Hey guys-
Just getting some ideas before I start pulling stuff apart.
I just bought my '92 GS500E on Saturday (day before yesterday). It has a running issue, so I want to get some advice.
To start it, you have to open the throttle. PO was using the throttle cable barrel adjuster to set the static throttle position open a little bit. Choke it and start it cold with the throttle wedged open a little bit with the barrel adjuster and it'll start and run fine.
Once it's warmed up, of course, even if you take it off choke, if you leave the throttle adjustment like this then it idles at 3-5K rpm. So the routine the PO was doing was to start and warm up the bike on the stand with the barrel adjuster opening the throttle a little, then once underway set the barrel back down flush and then when stopping the bike, bump the throttle to keep it from stalling.
PO had done a lot of work on the bike to get it mostly sorted out including rejetting and a bunch of other issues. But this was the remaining issue and he said he didn't bother getting it dialed in because he could make it work just fine by not letting it really drop to idle. In other words, you can keep it from stalling by blipping the throttle a little bit when it's idling.
OK.
So my thoughts on this are:
1. maybe when the PO did the jets, he lost one or both of the "tiny o-rings" and one or both are missing.
2. maybe the pilot jet is just way out of adjustment and there needs to be a lot more enrichment to start without doing the barrel-adjuster trick
3. maybe there's a vacuum leak somewhere (in addition to or instead of the tiny o-rings) ... PO suggested "airbox boots" whatever that is
4. maybe (probably) the idle is just set too low and if it were set higher it would not try to die at idle
It's been pouring rain constantly here in Austin so I haven't done any troubleshooting. Mostly I want to know what to look for when I get out there with wrenches in hand, if I get a few hours break from the rain while I actually have time to look at it.
Regarding the idle being too low, the PO says that it can't be set so that it will idle high enough to not stall. What does this tell you? What could this mean?
I did verify that the choke cable is connected and pulling correctly. Also if it matters, I did get the impression that the PO is being pretty honest abut everything and also is a reasonably capable mechanic. IOW, I have no reason to believe that he either screwed something up badly or he's trying to hide something. I'm assuming there's some honest mistake (like losing a tiny o-ring) or one more thing to fix (other vacuum leak etc.). I just don't want to spend a ton of time trying to chase this down. Besides this the bike is 100% sorted and ready to ride.
My current theory/plan is:
1. need to adjust the pilot jets (choke) so that it will start cold on choke without having to block the throttle open
2. probably there is a vacuum leak somewhere preventing it from idling without stalling ... find and fix ... and here's where I really need help on where to look
3. once I get #1 and #2 fixed or verified, if it still misbehaves, could this be valve adjustment? I'm not sure.
Ideas?
BTW when the PO changed the jets, he said he went "up one size" on the main jet. I have the exact info at home but not with me right now to verify. If it matters, the bike also has a stainless Yoshimura muffler from a GSX-R750 on it. I suspect the main jet is not related to the problem.
Thanks and sorry for the long post, my second post!
Welp, not much response yesterday...
I'm going to pull the tops off of the carbs and ensure the "little o-ring" is not missing. My research seems to indicate the running issue I have is most likely caused by these o-rings being MIA. Might as well double check, seems pretty easy to get to.
I'm talking the suzuki part number 13509-17C00 o-rings, "#10" in the service manual diagram, "vacuum port" o-ring, this one:
(http://www.litetek.co/images/OR-001_Fitment.png)
If my google-fu is any good, then this is a 3.0mm x 1.5mm o-ring (3.0mm ID, 6mm OD, 1.5mm CS). Finding a metric o-ring locally might be tricky. Anyone know if a standard #006 o-ring will work? That's 2.9mm ID and 1.78mm CS for a 6.46mm OD. If so then I can probably get those at a local hardware store, even Home Depot might have one.
You seem pretty knowledgeable so this might be a moot point, and I see that you said the PO said the idle cant be adjusted high enough that it doesn't die at idle, but did you try to adjust the idle screw yourself? I would at the very least try that, just on the off chance that the PO was wrong.
haha I only seem knowledgeable because I read a ton here on gstwins.com ...
EDIT
Alright, I pulled the tops off of the carbs and those "little o-rings" were in fact missing. But someone had tried to plug up the vacuum port on the top of the carb with goop of some kind. That was unexpected.
BTW a #006 o-ring from O'Reilly Auto Parts fits perfectly. $1.29 each and there's an O'Reilly on every corner it seems.
I did eventually get it to idle when it was warm but it still wants to stall. Also had a heck of a time starting it with the choke on. I am guessing maybe the idle mixture? But now it has the o-rings so at least that's done.
Well well, the intranets win again!
I managed to figure out who the PO of this bike is here on gstwins! A little bit of easy searching and I read his posts which detailed the mod/repair history of the bike. It's a gold mine of information.
Anyhoo, I realized that the PO did the "vacuum petcock delete" like this: http://gstwins.com/gsboard/index.php?topic=58895.0 However, I wasn't told about this so my starting troubles were probably due to flooding ... I didn't close the manual petcock when I parked the bike on Saturday. Or last night for that matter.
And ... I also discovered that the PO didn't change the pilot jets, but did drill the pilot mix screw covers and according to his posts, "backed them out to 2.5 turns" ... which also explains hard starting, difficult idling, etc., and maybe also the bogging at 1.5-2k rpm.
So I have some more work to do. For now, adjust the pilot mix screws and adjust the idle, try to improve idle quality as much as I can an get the bike to idle consistently without stalling or throttle blipping if possible. Longer term, get some 40 jets and swap them, along with a thorough carb cleaning and inspection for vacuum leaks after reassembly.
One question: where do I get new pilot jets? I have read that they should be like $3 each but Jets R Us has them for about $5.79-7.50 each. Is that the right place to get them and/or a decent price? I think this bike is literally going to nickel and dime me to death. Is this something I might be able to get locally (Austin TX) in order to avoid paying $10 for shipping?
Thanks!!
Learning a ton here. this forum is a great resource.
I guess I'm [almost] the only one talking in my thread. But maybe I'll eventually say something that causes someone who knows an answer to chime in.
Yesterday I tried adjusting the pilot mixture screws, first by putting them all the way in and then backing out four turns. The bike ran fine but really did not want to start or idle without throttle, even on choke. At first I thought it might still be lean. I rode it until it was fully warmed and then tried to adjust the pilot screws again and couldn't get it to change idle speeds via the screws. Then I pulled the plugs and they were super black. It's running rich at idle, clearly.
After I shut the bike off I began to go through the pile of removed parts from the bike that the PO gave me, which included the original pilot jets. I guess the PO did change the pilot jets.
I cleaned the plugs and put them back, then reset the pilot mix screws to 2.5 turns out. The bike would not start back up, choke or not, with or without throttle. The engine was still warm, it had only been sitting maybe 15 minutes since riding.
So, now I've fixed the vacuum leak, verified the choke works, set the idle so it'll idle when warm, but the pilot mix was way too rich which is likely what was causing it to want to idle at 3K rpm to begin with. I've never gotten it to start without a lot of throttle AND choke, and it won't start now. I'm kind of stumped. Next up I think I need to just let it cool and try to start it again, but I ordered new pilot jets so maybe I should just wait until they arrive and bite the bullet, pull the carbs and thoroughly clean them and ensure the correct pilot jets are installed. Get it back to a known good setting and with known clean carbs and fresh jets. The jets will probably arrive by Saturday.
Question: if the PO happened to install 40 pilot jets, then what is the initial pilot mixture setting that will enable it to start so I can tune the pilot mixture?
Oh, and I despise those pilot screws. Really needs a knurled knob or a T-handle. Getting a screwdriver bit on that is a gigantic pain.
I have absolutely no helpful information to add to your post. I just wanted you to know you are not being ignored! I am reading because I am fairly sure I am going to have to do similar things to my GS once my parts arrive. Thank you for the detailed questions/answers.
On a related note, yes getting a screwdriver in to those screws is a *insert profanity here*.
stock pilot jet is a 17.5 so if there is a 40 in the bike now then that is the problem. they go up in 2.5 increments so a 20 or 22.5 would work as these bikes are lean from the factory.
Quote from: grader on August 25, 2016, 06:18:59 AM
stock pilot jet is a 17.5 so if there is a 40 in the bike now then that is the problem.
This is a '92. I think the stock pilot is 37.5.
I also think it has the stock main jets in it now, but there is a set of 127.5 in the parts bucket, and according to the PO's messages on the forum here, it sounds like he tried the 127.5s and went back to the stock. Or it's possible there are 125s in it now. Hardly matters, because the bike runs great at >1/4 throttle. All of my current running issues are at idle, light throttle, and low-speed (<2k rpm).
Quote from: Lbx! on August 25, 2016, 06:07:11 AM
I have absolutely no helpful information to add to your post. I just wanted you to know you are not being ignored! I am reading because I am fairly sure I am going to have to do similar things to my GS once my parts arrive. Thank you for the detailed questions/answers.
Hope this is helpful then. Since it's likely to rain all weekend this weekend, I think I'll plan to tear everything down and clean the carbs, change the pilot jets (assuming I get new ones by Sat AM), and I have some other stuff to do (change the ignition switch, handlebar and fuel cap, replace the tank bolts with correct bolt and maybe retap one hole, etc.). Might as well just tear it all the way down, then I can set the initial pilot needle position with the carbs upside-down on the bench where I can see the screw heads and easily count turns.
I assume 2.5 turns out is still the correct initial position.
The instructions for setting the pilot jet screw position generally are like this:
1. start and warm up the bike
2. set the idle at 1500+
3. turn the pilot screw out until revs stop increasing and then turn out another 1/4 turn
4. repeat 2-3 on the next carb
5. set the idle back to 1200ish
Now, my problem is that turning the pilot needle screw out does not increase revs. So I assume I can go backwards here, right? Set the idle at like 1500-2k, then turn the pilot screw IN until revs begin to DECREASE, then repeat with the next carb. Now do steps 2-4 on both carbs again.
My current theory is that the PO left out the "little" o-rings causing a vacuum leak at idle, resulting in a really lean mixture at idle. So he probably set the pilot needle really rich to compensate, which resulted in making it barely run at idle (closed throttle) but once the throttle opened the extra air from the vacuum leak was insignificant so it ran super rich while in the pilot circuit. This is why I had bad running (hesitation/bogging) at 1.5-2K rpms and also why the bike could not be set where it would idle below about 3000 rpm. Opening the throttle enough to get air in the throat of the carb resulted in a 3k rpm idle due to the super rich pilot jet setting, and backing out the idle enough to reduce below 3K rpm closed the throttle enough to make it run super lean due to the vacuum leak.
I fixed the vacuum leak and then the bike could idle but it was really, really rich, which is why it wouldn't start on choke and would die when I put it on choke even when cold. And it stalled at idle when warmed up. I initially (without checking the plugs) thought it might still be lean at idle and made matters worse by adjusting the pilot jet more rich. By the time I got half a clue what was going on, the bike was already hot and would not start because it was likely flooded or who knows what.
I'm going to steel myself to "do it right the first time" and go ahead and tear everything down, clean, rejet, and put it all back together by the book. That way I can verify everything is done right, or at least I can stop blaming the PO for what might be done wrong.
You guys can follow along and see what I find. I am sure a lot of these 25 year old bikes are in a similar state.
I'm not a huge wrench turner and am also a new GS owner, so i'm learning a lot reading your thread. Thanks for keeping us up to date on how your troubleshooting is going. I'm sure i'll use this information in the future. good luck!
Quote from: SirHansford on August 25, 2016, 11:44:12 AM
I'm not a huge wrench turner and am also a new GS owner, so i'm learning a lot reading your thread. Thanks for keeping us up to date on how your troubleshooting is going. I'm sure i'll use this information in the future. good luck!
Yeah I think the real key is that when the PO rejetted the carbs he left out the little o-rings and then that started a crazy wild goose chase to try and get it to run right, resulting in nearly everything being set wrong.
For those who have been following along, here's the current state.
I tore down the carbs over the weekend to check what was up. I found a lot of things along the way. Lesson here is: you never know what the previous owners might have done right or wrong to the bike, so best to make sure and do the work right yourself. Or at least make sure compromises you make are those you have chosen for yourself, so you won't go nuts trying to debug something with no information on what might have been done wrong.
First thing I found was the vacuum hose going to the petcock was not in fact a vacuum hose. It was a fuel hose, and it was making a poor seal on the carb. So this is likely another source of a vacuum leak.
Next I found that neither the airbox boot clamps nor the carb boot clamps were tight (!). No wonder the thing wasn't working right.
Went to drain the carbs, one of them was missing the drain screw and the hole it goes in was filled in with goop... looks like epoxy. Brilliant.
Carbs torn down on the bench, the pilot jets had already been replaced with 40s. I put them right back. The main jets were the originals (122.5). The PO gave me a little envelope labeled "GS500 Jets" that had the original pilot jets and a set of 127.5 main jets in it... my guess is he originally got 40/127.5 set to use, could not make it run right with the 127.5s installed due to his numerous vacuum leaks, and put the 122.5s back in. I swapped them to the 127.5s.
There was some buildup of some white and tan crusty junk all over the bowl seal surface on both sides. I let the bowls soak in Dawn+water for about 24 hours then cleaned up with the Dremel with a nylon brush bit. The float o-rings were cracked and hardened and would not hold the floats in place, and the o-rings I had here were too fat and I couldn't get them to fit back together with the new ones. I have to order more o-rings but for the time being I made a game-time decision to put it back together with permatex just so it will run. Yes, I know I will have to tear them down again!
Float height was not even close to right, far as I could tell. Probably off by 3-5mm (high). No wonder it was flooding.
Everything was clean and good to go so I buttoned it back up. I didn't take the tops off since I had just done that the other day, and I knew the o-rings were good and everything was good to go. Dunno if there are shims/washers on the needles. We'll see how it runs. Easy enough to get to that part if I need to check or change it.
I set the pilot screws to out one turn, since there are 40 pilot jets and it was running poorly with them out 2.5 turns before.
Getting it back together was a colossal PITA. That freakin' airbox! I'm ordering a pair of pods right away! But one thing I DID discover is that to get the airbox back on, it REALLY helps to take the air filter OUT, and then push the airbox flanges onto the carbs from the inside of the airbox by reaching in the air filter hole. This literally took me over an hour to get the airbox on. I wound up actually pulling the carbs back off and putting the airbox on the carbs first then cramming it all back on together, which was easier, but not close to easy.
I added a blob of permatex on each of the broken-off carb top vacuum ports just for good measure, I don't want it to leak. Gotta order some new carb tops, or even find some used/broken or maybe a pair of carbs that are in bad shape so I can use them for parts, including these tops. And a new bowl for the one with the missing drain screw.
The PO had added an inline fuel filter and I debated heavily whether to chunk it. If I had any extra fuel hose on hand I would have just tossed it, but I didn't, so I didn't. But, I found that the fuel filter was really what was causing all of this to be so hard to assemble. There's just not room under there for a fuel filter along with everything else. With a lunchbox or pods it would be fine. If I wind up having to pull it all apart again, I'm putting new carb tops on, pod filters, and probably redoiing all of the fuel hoses and maybe change the type of fuel filter as well. I'll be shocked if that fuel filter is not pressing on a fuel hose causing it to be restricted while it's running. But there's no space to even get a light in and look so who knows? We'll find out when it runs.
Took surprisingly long to get the carbs primed but once it was all back together and I cranked it about 50 times it started right up. On choke! Which it wouldn't do before! I had to bump the throttle a little to get it to start but nothing like before. I started fiddling with the idle adjustment almost immediately and found that once it had been running like 30 seconds I took it off choke and it was idling at 5K rpm. I backed it off and got the idle close to right... I just had a few minutes to fool with it. But then I turned it off and the ultimate test. 5 minutes later I tried to restart and what do you know? It fired right up! Great news. Now at least I can ride it to the gas station, get gas, and not have to get a truck to take me home.
I still need to reset the pilot needles but at one turn out at least it was running far better than before.
Here's a question for the experts: what does it mean when it is slow to return to idle? I rev it and it comes down to like 3.5K rpm and then slowly (3-5 seconds) returns to idle. I am guessing it's coming off the main circuit and going to the pilot circuit and it is telling me it's still rich on pilot ... ? Also it seems to idle faster OFF choke, even when cold, so that's probably telling me the pilot is still rich. Am I on the right track here?
One thing's for sure, I know my way around the carbs a lot better and feel pretty comfortable working on it now. Well worth it. I think just a few minutes adjusting the idle and pilot mixture and I'll be in business. Eventually I'll have to pull it all apart again and put in new float o-rings but I'll probably wait until I can get new carb tops and a replacement carb bowl before I do that, that is assuming I can get it to run acceptably. The goal here is not to make the bike awesome. It's to make it reliable and usable to ride 100 miles a month over the next few months. This is Texas and we expect a far milder than normal winter, meaning it'll be highs in the 70s and lows in the 50s even in January. That sounds like perfect motorbike weather to me.
I'll update whether I can get the pilot screws and idle set right after I have a few more minutes to play with it.
Have fun and keep the revs up.
I've been following along with this post, have had nothing helpful to say. But I'm cheering for you! Glad to hear you had some success over the weekend!
Quote from: mr72 on August 29, 2016, 04:47:37 AM
...
Here's a question for the experts: what does it mean when it is slow to return to idle? I rev it and it comes down to like 3.5K rpm and then slowly (3-5 seconds) returns to idle. I am guessing it's coming off the main circuit and going to the pilot circuit and it is telling me it's still rich on pilot ... ? Also it seems to idle faster OFF choke, even when cold, so that's probably telling me the pilot is still rich. Am I on the right track here?
...
Slow return to idle is a lean condition as far as I know. The way the choke works (if I remember correctly, could have this backwards, so maybe double check what I'm saying lol) is that "opening" the choke, is actually
restricting airflow, if effect creating a richer condition (so really, youre "closing" the choke, rather than opening it). Then, as the engine warms up, you can take the choke "off", returning the fuel/air mix back to normal, which is normally a leaner condition..
Idling faster off choke and being slow returning to idle sounds to me like your fuel-air mixture is too lean. Try adjusting that, after making sure my memory isn't mixing up the way the choke works haha.
ETA:
Quick googling: seems to me that my memory is correct, but I did find this on Yahoo Answers: "Modern carburetors typically provide a rich start mixture by means of an orifice which supplies extra fuel. The orifice is normally covered by a piston which is moved by operation of the "choke" lever." Not sure if this is the case on the GS500, but its essentially the same thing: in a normal functioning engine, the further the choke lever is "open", the richer the fuel/air mix is. So, if youre getting higher RPMs with choke off at idle, and it is slow to return to idle, I would bet your f/a mix is too lean.
Found this thread too, seems to confirm the above http://gstwins.com/gsboard/index.php?topic=21206.0
Quote from: qcbaker on August 29, 2016, 07:49:28 AM
Slow return to idle is a lean condition as far as I know.
And the internet confirms your assessment.
Actually I'll be quite pleased if it's lean, because before I tore it all down it was running so rich at idle that it would die and refuse to start up again when it was hot... it would really only run close to right when it was stone cold.
Quoteis that "opening" the choke, is actually restricting airflow, if effect creating a richer condition...
...but I did find this on Yahoo Answers: "Modern carburetors typically provide a rich start mixture by means of an orifice which supplies extra fuel.
Yeah I think the GS carb actually adds fuel when on choke as opposed to the traditional choke that closes the air inlet by some degree (to see in real easy action look at a weed eater :) ). No matter. I can adjust the mixture at idle. I only have the pilot needle backed out one turn right now, so lean running would not be surprising and it's easily fixed.
By the way today I bought one of these http://www.harborfreight.com/8-piece-right-angle-screwdriver-92630.html to adjust the idle mixture.
(http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/9/2/92630_zzz_500.jpg.jpeg)
Idea is to use the "handle" to hold the bit in place and turn the knurled knob on the back of the tool to make adjustments. With the ratchet it's 20 clicks for one turn, so you can set it 1/4 turn by 5 clicks etc. Let's see if it works. Could make my life a whole lot easier. Man that screw is a huge pain to get to with ordinary tools.
I have everything I need to put it all back together now this afternoon. Kind of excited about it actually.
Quote from: mr72 on August 29, 2016, 11:27:34 AM
...
I have everything I need to put it all back together now this afternoon. Kind of excited about it actually.
Hopefully you get everything back in order. Happy to be of some kind of help lol.
I'm in the same boat as Torstein... been following along but haven't had anything helpful to add... except good luck!!!
And also, thank you for sharing your experience... it may very well help others in the future :thumb:
Okay guys, here's the way it is.
I put it all back together and it started right up, no sweat. I had the pilot mix screws turned 1 turn out. Once the bike began to warm up, I took it off choke and the idle was like 4000 rpm. I adjusted it down and set to try to set the mixture screws.
Recapping ... I just pulled the carbs and cleaned and put them back together with 40 pilot and 127.5 main jets. Bike would not start when hot before and would not idle when warmed up. Previously it had 122.5 mains with the 40 pilot jets. It also had numerous opportunities for vacuum leaks.
Here's the current behavior:
- when I first started it, while it was warming up, it would be delayed idling down. Rev it to >7K and on the way back down it would hang at 3-4K for like 5 seconds and then return to ordinary idle. This was with the pilot mix screws set to one turn out. Right now, this is looking like a good place to go back to.
- I went about setting the idle mix screws once warmed up and by the book, that is 1/4 turn past where the idle stops increasing, they are each set about 3 turns out.
- when warmed up (or cold, actually), rev it on the stand and it will NOT idle down. It stays at 4-5K rpm. If I briefly turn on the choke it will return to idle and when I turn the choke back off, it will stay at idle. So it will idle off-choke, but only after I "blip" the choke on and off.
- the right carb idle mix screw seems to have no effect(!) ... could be that I backed it out so much that it now is as rich as it'll get and backing out more makes no difference
I know everyone said that delayed idling down indicates lean. Now I think I have it way rich. When we say hanging idle means lean, are we talking about a full turn on the mix screw or 1/4 turn or less?
Quote from: mr72 on August 30, 2016, 07:43:18 AM
...
- when warmed up (or cold, actually), rev it on the stand and it will NOT idle down. It stays at 4-5K rpm. If I briefly turn on the choke it will return to idle and when I turn the choke back off, it will stay at idle. So it will idle off-choke, but only after I "blip" the choke on and off.
...
I know everyone said that delayed idling down indicates lean. Now I think I have it way rich. When we say hanging idle means lean, are we talking about a full turn on the mix screw or 1/4 turn or less?
Based on our discussion about chokes earlier, "blipping" the choke on would make the mixture richer for a second. If that causes the bike to return to idle properly, then to me that still indicates that the bike is running lean, not rich.
Are you absolutely sure you've eliminated the possibility of a vacuum leak somewhere?
Quote from: qcbaker on August 30, 2016, 07:57:16 AM
Based on our discussion about chokes earlier, "blipping" the choke on would make the mixture richer for a second. If that causes the bike to return to idle properly, then to me that still indicates that the bike is running lean, not rich.
On the contrary, if I leave the choke on, that is I don't "blip" it, then the bike will die. I think it's just not returning to the pilot circuit AT ALL until I turn on the choke, which makes it run so rich it wants to die, and this causes the revs to go down and if I turn the choke back off when it gets to idle then it'll continue to idle.
It really feels like the bike just only is running in the main circuit and you have to force it to go to pilot by getting it to stall.
Come to think of it, a gross vacuum leak could cause this... that is air getting in other than the throttle plate.
Quote
Are you absolutely sure you've eliminated the possibility of a vacuum leak somewhere?
Nope! But it's not exactly easy to check. How long will it run with the tank off? I think the tank has to be off in order for me to really check for vacuum leaks. I suspect the repaired hole where the balance vacuum ports used to be in the carb covers might be leaking still. And there are a hundred other places it could be leaking but to get any carb cleaner sprayed on there requires the tank to be off.
ALSO I just remembered, there was a drop of fuel on my screwdriver bit when adjusting the pilot mix screws. Is it possible a bad pilot needle o-ring could be causing this? Talking #17 in this picture:
(http://www.southbayriders.com/forums/attachments/347826/)
If so, what's the spec/size of that o-ring?
I'm sorry, I don't think I'm knowledgeable enough about the carbs to be of much real help here... :dunno_black:
Everything from here on out is speculation on a subject I have limited knowledge of:
The only thing I can think of is that the pilot jet is very rich, but you also have a vacuum leak somewhere, causing the bike to run lean when on the main circuit and rich when on the pilot circuit? I'm not sure if that's even possible lol
Quote from: qcbaker on August 30, 2016, 10:17:06 AM
I'm sorry, I don't think I'm knowledgeable enough about the carbs to be of much real help here... :dunno_black:
Well I'm not very knowledgeable about carbs and especially not this one but I am above average even among gearheads on this general topic... although I'd be far more comfortable working on the fuel map via a computer and megasquirt :) I did do a ton of work with my 240Z carburetors long ago and they are similar enough to this that it's easy enough to translate.
Quote
Everything from here on out is speculation on a subject I have limited knowledge of:
The only thing I can think of is that the pilot jet is very rich, but you also have a vacuum leak somewhere, causing the bike to run lean when on the main circuit and rich when on the pilot circuit? I'm not sure if that's even possible lol
Yeah I think it's definitely NOT running lean in the main circuit. I haven't ridden it on the road since I got it back together with the 127.5 jets but I think with 127.5s and the stock airbox it's highly unlikely to run lean on the main jet.
But it MIGHT be lean on the pilot jet, but REAL lean at idle due to a vacuum leak.
My current (questionable) theory is that at small throttle opening (idle) there is air getting in one or more places where it shouldn't ... maybe the pilot needle o-ring or some other vacuum leak, and this causes it to run lean at idle no matter what I do. This entices me to adjust it way too rich. So when the throttle is closed it causes a big vacuum condition and sucks in a lot of extra air through the vacuum leaks and makes the revs hang, since the pilot is adjusted so rich that there's plenty of fuel to mix with the vacuum-leak air and keep the revs up even though the throttle is [mostly] closed. If I do something like choke it or even if I were to ride it and let it roll in gear and pull the brake, then once the revs get down low enough there's not enough vacuum to suck much air in and it returns to idle, but since it's leaking in air, it's very lean so it won't idle at a the correct speed and it tries to stall.
Basically I think the problem is likely continued vacuum leaks and possibly bad (or missing!) o-rings on the pilot mixture needles.
I ordered a pair of o-rings for the mixture needles and also new o-rings for the floats. Today I am going to pull the tank and pull the carb covers and re-seal that broken-off vacuum port on each one, plus make sure the slides are not sticking (wouldn't that be a kicker ...). With any luck I can get it to run well enough to ride a bit until the o-rings come in and maybe by the weekend I can take it apart and replace the o-rings.
I have a MSF course coming up in abut 10 days and I have ridden maybe 30 minutes on this bike, the only riding I've done in 20 years. I need it to run well enough to get a little practice operating the controls in before the MSF course. It's a bit scary riding a motorcycle that tries to idle at 4-5K rpm! The minimum speed in gear is like 30 mph! Right now it will run and idle (mixture needles set 1/2 turn out or less) but it wants to stall so I have to blip the throttle when it's sitting still. I think that's good enough to practice riding but not good enough to leave the neighborhood.
Quote from: mr72 on August 30, 2016, 10:51:49 AM
...
I have a MSF course coming up in abut 10 days and I have ridden maybe 30 minutes on this bike, the only riding I've done in 20 years. I need it to run well enough to get a little practice operating the controls in before the MSF course. It's a bit scary riding a motorcycle that tries to idle at 4-5K rpm! The minimum speed in gear is like 30 mph! Right now it will run and idle (mixture needles set 1/2 turn out or less) but it wants to stall so I have to blip the throttle when it's sitting still. I think that's good enough to practice riding but not good enough to leave the neighborhood.
Well, it sounds like you have a better idea of whats going on in the carbs than I would lol. As for your MSF course, are you taking the Basic or Advanced course? If you're taking the Basic course, a lot of places will have bikes for you to ride there. I think the Advanced course you have to take your own bike, though.
I'm taking basic, and they provide motorcycles. But I just need to retrain my hands and feet to work correctly on a motorcycle. I found my muscle memory was confused after 20 years of avid cycling, so I just need to get some parking lot minutes in, get the coordination of my hands and feet back where they were when I was a kid.
I had a similar experience when I bought my GSF. I rode dirt bikes every summer for like 8 years when I was younger. I hadn't ridden for about 6 years when I bought my GS, and my first time pulling off from a stop was a bit jerky, but I didn't stall or drop the bike. Felt like I just needed to remind my hands and feet how to operate the bike, then after a couple rides I found that I got back into it pretty quickly. Once you fix up your gremlins, I'm sure you'll get back into the swing of things fairly quickly. It's like they say: "you never really forget how to ride a bike" lol.
Well my problem is that for the 20 years while I have not been riding motorcycles I have been riding bicycles, mostly mountain biking, like 5-10 hours a week. So my hands really think they know what they are doing, but they are trying to do two incompatible things... grab all the lever with your left hand at a stop, which you'd NEVER do on a mountain bike unless you really are in love with that head injury, and the dive you get from pulling the right lever just feels all wrong. It'll just take me a few miles to get it back into the groove.
It's kind of like trying to drive a RHD car on the left hand side of the road.
Last night I worked on this a little more.
I tried spraying carb cleaner all over the carbs, intake boots, etc. to see if a vacuum leak would reveal itself. It didn't.
I noticed there was no cap on the right carb vacuum port, and I know it's supposed to be internally blocked off but I went ahead and put a cover on it, which didn't help.
I am about sick of taking this tank on and off! It's a huge pain to get the bolt holes to align to get it back on, since most likely one of the POs bent the bracket. But it's coming off again, because again I think there HAS to be a vacuum leak somewhere causing this issue. So I'm going to give it one last ditch effort to repair.
I ordered o-rings for the floats and the idle mix needles, after finding an amazingly cheap source. They are on the way. Hopefully they get here by the weekend so I can get the bike together and try it when I have some time.
I didn't investigate whether the diaphragms are leaking or whether the slides are working. I think a leaking diaphragm would have the opposite problem ... the bike would not want to rev UP from idle. But a sticking slide (or two) might cause the hanging idle, no?
Also, someone has put goop of some kind, like epoxy maybe? all over the attachment points of the little brass tube on one of the carbs.... the part you see here to the left of the vacuum port and throttle shaft:
(http://i205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/Mikuni%20BST33SS%20Carbs/rightside-1.jpg)
I imagine they put the goop on there because there was a leak. Is this vacuum or fuel?
So here's the current condition:
There is some elusive set of mixture/idle adjustment conditions wherein the bike will idle with the dreaded "hanging idle" symptom. When set like this, I still have to nurse the throttle to keep it from dying.
Much more common is the condition where it won't return to idle. It hangs up at like 5K and won't idle down on its own. You have to do something to force it like apply the choke briefly or (presumably) let out the clutch a little to try to stall it.
OR I can set the idle lower and it won't hang up at 5K but instead it just won't idle, it dies if you don't constantly hold the throttle open a little bit.
We're talking like 1/8 of a turn of the idle speed adjuster difference between 5K-hanging-idle and won't-idle-dies.
Basically this is exactly what it was doing when I got the bike.
Since I discovered the missing vacuum port o-rings and replaced them, AND there was no real change in behavior, I think I can safely assume there is still a big vacuum leak.
My next move is to pull the carb caps back off and revisit the plugging of the vacuum ports (recall, they were broken off some time in the bike's history and a PO "plugged" the holes with some kind of goop like permatex). I figure eventually, if I can get the bike to run quasi-reliably and don't end up throwing it off a bridge somewhere, I should replace the tops but they are kind of expensive and something tells me I might have to replace the entire carbs. So I am going to just redo the plugging of these ports, hopefully do a better job and ensure there is no way they can still leak.
WHERE ELSE SHOULD I BE CHECKING FOR A VACUUM LEAK?
1. Vacuum ports (one on top of each carb, one on side of each carb [petcock])
2. intake boots
3. ?? where else?!?
I saw this while browsing the wiki, sounds kind of like some of the symptoms you're having
http://wiki.gstwins.com/index.php?n=Troubleshooting.BikeRunsBadly
maybe it will point you in the right direction.
Quote from: qcbaker on August 31, 2016, 08:52:37 AM
I saw this while browsing the wiki, sounds kind of like some of the symptoms you're having
http://wiki.gstwins.com/index.php?n=Troubleshooting.BikeRunsBadly
maybe it will point you in the right direction.
BTDT ... a lot.
I cleaned the pilot jets manually and replaced the mains.
I have a new set of pilot jets here and I think I'll replace them for good measure when I have the carbs off again probably this weekend.
Since I read your post quite fast I did not notice if you checked that the left carb vacuum port is capped where a hose would connect to the original petcock.
Good job fiding that those 2 little o-rings on top were missing.
I also capped the right carb vacuum on my bike just for good measure :D
Do you get RPM fluctuation when you stop at a traffic light for example?
Quick tip: When diagnosing I like to have the bike on the center stand (horizontal)
Inspect the intake boots, if the rubber is dry you can have a leak there.
Do not put your tank on and off (I have done that about 10 times last month), find a way to feed the bike with fuel. With a small bottle or so connected to the carbs fuel line.
Start your bike without the airbox with a bit of choke since she will not run without choke this way, listen to the engine running, are there any RPM changes?
Spray break cleaner to the intake boots -> RPM changes?
Go ahead and make yourself a simple tool to equalise your carbs (with the airbox!) just for good measure. If you can't equalise there is a leak somewhere
(:star: careful since the leak could be in your equalising tool!! been there done that ahah)
With patient and persistence you will fix it! :cheers:
Quote from: crazydred on August 31, 2016, 09:38:00 AM
Since I read your post quite fast I did not notice if you checked that the left carb vacuum port is capped where a hose would connect to the original petcock.
I didn't bother to update, but it appears the original petcock was put back and actually working properly, except that the PO had put vinyl fuel hose in place of the vacuum hose so it was quite obviously not only leaking but incapable of holding a vacuum. I replaced the hose.
Quote
Good job fiding that those 2 little o-rings on top were missing.
Searching this forum showed me where to look. However, I think this still may be the cause of my vacuum leak because of a crummy job sealing the remnant of the broken-off vacuum ports.
I should take a picture and post it, where the vac ports are broken off and sealed off. It's going to make balancing the carbs a little more tricky. I'm gonna have to use my old uni-syn. :)
Quote
I also capped the right carb vacuum on my bike just for good measure :D
While I have the carbs off next time I think I'll tap the hole and put a screw in it with blue loctite just to make dang frikin' sure it doesn't leak. Or maybe I'll just fill it with JB Quik.
Annnd... searching the internets popped up some kind of good ideas on sealing vacuum leaks on stuff in CV carbs bikes, like painting rubber parts that may have stretched or may have tiny surface cracks with plasti-dip, such as the intake boots. I figure these must be easy to get off of there anyway once the carbs are off so I will likely pull them and check to make sure there's not a leaking o-ring or cracks.
Quote
Do you get RPM fluctuation when you stop at a traffic light for example?
Well, I'm not riding the bike. I've only actually ridden it maybe 20 minutes total since I got it, and not at all since I put the carbs back over the weekend. This is because of the inconsistent idle.
But it doesn't seem to fluctuate. It either will be hanging idle that delays to rev down, or if I enrichen the pilot enough to prevent that, then it can't be set to idle other than 4-5K rpm or too low to keep the bike running.
Quote
Quick tip: You can check for air leaks by spraying brake cleaner to the carbs while the bike is running. If RPM changes you have a leak.
When diagnosing I like to have the bike on the center stand (horizontal)
I did this, of course, with carb cleaner and not brake cleaner. There was no leak evident. I may try it again, being more attentive around the intake boots. Would be way easier if the bike were elevated 4 ft. in the air :)
Quote from: mr72 on August 31, 2016, 09:58:04 AM
Do you get RPM fluctuation when you stop at a traffic light for example?
This is because of the inconsistent idle.
But it doesn't seem to fluctuate. It either will be hanging idle that delays to rev down, or if I enrichen the pilot enough to prevent that, then it can't be set to idle other than 4-5K rpm or too low to keep the bike running.
If the RPM does not come down from 4k you have an air leak, on my case the airbox was no connected properly to the carbs!
Post a picture of the broken carb top :)
Quote from: crazydred on August 31, 2016, 09:53:34 AM
Inspect the intake boots, if the rubber is dry you can have a leak there.
Right, that's one thing I have not yet checked.
Quote
Do not put your tank on and off (I have done that about 10 times last month), find a way to feed the bike with fuel. With a small bottle or so connected to the carbs fuel line.
Good idea.
Quote
Start your bike without the airbox with a bit of choke since she will not run without choke this way, listen to the engine running, are there any RPM changes?
Spray break cleaner to the intake boots -> RPM changes?
Another good idea :)
Quote
Go ahead and make yourself a simple tool to equalise your carbs (with the airbox!) just for good measure. If you can't equalise there is a leak somewhere
I have (somewhere in my collection of vintage tools!) a uni-syn carb synchronizing tool. I just have to dig it up. But I need to get the thing basically running right first. Since the carb-sync vacuum ports are broken off/sealed up from my carbs, the preferred simple method to balance them is not available.
Quote
With patient and persistence you will fix it! :cheers:
I'm pretty confident of that. It's just whether I have a sufficient quantity of patience and persistence to invest!
Quote from: crazydred on August 31, 2016, 10:03:50 AM
If the RPM does not come down from 4k you have an air leak, on my case the airbox was no connected properly to the carbs!
I can see how that's highly possible, but in my case I attached the carbs to the airbox before fitting the carbs to the intake boots, so I am 100% sure they are completely and fully connected. But I suppose it's possible I have a crack or air leak in the airbox somewhere, such as the interface between the rubber air horns and the air box. I intend to eliminate this possibility in the near future with pod filters.
Quote
Post a picture of the broken carb top :)
Will do. In fact, it turns out I have the evening to myself today after work so I might actually dig into this yet again. I'll take the time to take pictures.
I still think there's one or more air/vacuum leaks that is causing ALL of this trouble. With 25-year-old rubber parts, it's not surprising. But it is a huge PITA to track down.
Well I must say that your bike is older than me and I would be glad to see it running properly again ahaha :icon_lol:
When you post some pics we can analyze the damage :)
Quote from: crazydred on August 31, 2016, 12:03:29 PM
Well I must say that your bike is older than me and I would be glad to see it running properly again ahaha :icon_lol:
It'll be running properly again eventually, that's for sure.
I mean, I have been working on cars and small engines for far longer than this bike has existed. First motorcycle I nursed back to functional state from non-running state was a mid-70s Yamaha DT80 that I fixed when I was 12 ... that was 1985. The next summer we resurrected a 70s Honda Z50A, well sort of, it was missing the right side engine cover and we never replaced it. But boy did it run. And throughout my teens and 20s I did lots of work on carbureted cars including my 240Z and a couple of VWs my brother had and some friends' Z cars. ... and I think I've worked on countless weed eaters, lawn mowers, leaf blowers, chainsaws, mini-bikes, go-carts, engines bolted to bicycles, mopeds, you name it. Guess I always had a knack for this and I've been at it for three decades.
I'll get it eventually. Just need the collective here to help me skip a lot of steps. It took me a month of daily tinkering to get that DT80 running nowadays I'm not some kid on summer vacation where I can go tinker with something all day every day for a month. I need to get this bike working right in hours, not weeks or months. And I think that's even possible!
OK this evening's update.
I took the carbs off after running the bike out of gas with the tank and airbox off spraying carb cleaner over everything trying to find a vacuum leak where none could be found.
Took the carbs apart again and here's what's up, so far.
- the o-rings on the mixture needles were shot. Both are flat as a pancake. New ones on the truck.
- the boots connecting the carbs to the engine are in mint condition. No way they are leaking. They are perfect.
- the carb tops where the vacuum ports are broken off... first I inspected the broken off spot where the holes were filled in. Looked like solid work. Then I poked a screwdriver through the "goop" that had filled in the holes, and lo and behold, it was some kind of ... wax? grease? who knows. Somewhere between old grease and wax. About the consistency of peanut butter. NOT GOOD. I cleaned the holes out really good, put a piece of masking tape on the inside and then filled the holes with JB Clear epoxy.
Carb tops with original goop:
(https://4.bp.blogspot.com/-7aYBf--ZQhU/V8gPbzv8jgI/AAAAAAAAECs/6wMGAHe-oWQqFil3yOsbOupM0YomzoG-wCLcB/s1600/2016-08-31%2B19.33.50.jpg)
Carb tops with epoxy setting up:
(https://4.bp.blogspot.com/-veUqXA99Ixg/V8gPgzo4nlI/AAAAAAAAECw/N4f3WgYNmH8frF06P4eqJaxVGvPgZejBwCLcB/s1600/2016-08-31%2B19.44.15.jpg)
- ran a 0.013" guitar string through most of the orifices and channels of the carb and sprayed everything with carb cleaner. Carb looks to be good to go besides the float o-rings, needle o-rings, and of course that disaster of broken off vacuum ports.
I actually feel good about it now. I inspected the carbs and couldn't find anywhere else that a leak may be happening. Everything seems to be working fine. One of the diaphragms looks a touch dodgy but no pinholes or other issues. Slides move like they should. Needles are fine. I replaced the old (new looking) pilot jets with a new pair just for good measure. Should get the o rings by the weekend or so and be able to put it together and see how it runs. If it doesn't run mostly right after this, then I will be truly lost.
Truly I think 99% of the problem was the waxy goop in the vacuum ports, and the other 1% was bad o-rings on the mixture needles. Getting rid of the airbox in favor of pods will just remove chances for stuff to leak and make assembly far easier.
Good job man, you are going the right way :thumb:
I got everything back together and I am back to the drawing board.
Replaced all of the carb o rings, intake boot o rings, thoroughly cleaned the carbs and set the float height. Put in 40/127.5 jets. Set the idle mixture to 2.5 turns out. Left the stock air box.
Bike started fine and warming up in the garage seemed to run great. I thought I had fixed it. Then I rode it and the idle was hanging up at 3k. I can't adjust it so it doesn't hang at 3k without being too low to stay running. The idle is not really consistent.
Finally I started toying with the idle mix and now it won't start when hot. I am going to set it back to like 3.5 turns out once it cools and try again. I managed to get it running well enough as long as I nurse the throttle when stopped. I am close to thinking that's as good as it will get.
Ideas? BTW I am absolutely sure there is no vacuum leak. And I hate carburetors.
---EDIT---
Well, after sleeping on it and mulling the problem most of the afternoon yesterday I think the problem is that I might have had the mixture nearly spot on but then I adjusted it too far. And maybe the carbs need balancing and the valves need adjusting and I just don't have patience to do that all right now, while I do have patience to ride it with a slightly iffy idle.
So I set it back to 2.5 turns and when I get to ride again I'll set the idle speed so that it requires the occasional throttle bump to keep running and then leave it alone until I can make time to adjust the valves and sync the carbs and then see if I can make finer adjustments to the low-speed mixture to get it to idle better. Right now this bike with 20K miles on it has just too many little things that have been neglected, I am afraid I probably can't get it perfect with just the carbs.
OK, I'll keep talking to myself here. Perhaps it helps some of you who follow along :)
I think I have been doing three things wrong:
1. expecting the bike to run right without any quirks even though it's 25 years old with 21K miles which may need valve adjustment and carb sync to be the best it can be
2. making adjustments before it was fully warmed up after a 15+ minute ride on the road
3. making too-coarse adjustments to the idle mixture... I was turning the screw 1/2 turn at a time
Oh and the other things I am doing wrong is being way too impatient and ignoring my instincts.
I read two other sites' posts that helped me a lot, maybe they are of use to you guys:
http://alt.motorcycle.sportbike.narkive.com/oHTaYnXK/blip-throttle-and-revs-hang-rich-lean
http://www.thegsresources.com/_forum/showthread.php?199096-Adjusting-the-Idle-Mixture-on-CV-Carbs
My gut tells me the bike is running rich at idle when fully warmed up. I can smell it, and it feels like other engines I have worked on that are rich. It may be totally ok for it to be running rich, especially considering it's summer and very hot and it'll lean out in winter, as long as I can keep it running at idle.
The hanging idle or slow return to idle I think was happening when the bike was not fully warmed up but off choke. I think I have been in too much of a hurry and assumed it was warmed up before it truly was. I just need to keep it on choke longer.
I really think it's running rich, but it's close. I can't ride this daily or even close. After I finish my MSF course this weekend I figure I'll be on pace to ride maybe once a week, very rarely a second time in a week. I just need to get it to where it will start when it's hot and it idles low enough that I can stop the bike without it revving itself. Then I can tweak it after my next real long ride while the engine is fully warmed up, and maybe lean out the idle mixture 1/4 turn max on each ride until it's right on.
Main thing is, if I can get it back to where it was on Saturday after I put it together, that is running fine but idling too low and you have to nurse the throttle a touch to keep it running, then that's probably good enough that I can work it 1/8 or 1/4 turn at a time every half hour of ride time until it gets more perfect or until later I can make time to adjust the valves and sync the carbs. It may never idle without bumping the throttle until I can adjust the valves and sync the carbs.
Update --
I rode it today until it was fully warmed up, then stopped a few times and set the idle speed. Once I got it home it was well warmed up (maybe 20 minute ride) and it was doing a little hanging idle. I wound up adjusting the mixture screws to a total of 3-1/4 turns out and there is minimal hanging idle and it will idle well as long as you are willing to occasionally bump the throttle.
Funny thing is, this is basically how it was running when I got it. But when I got it, it had a bad stumble and hesitation under 2K rpm and now it pulls great from idle on up. I never revved it over about 6K in the whole ride (all max 35mph streets neighborhood). I think the next step is to adjust the valves, which likely has never been done, and go from there.
Some things to take away:
- Adjusting the idle at anything but fully warmed up conditions is a fool's errand
- There are a ton of places for vacuum leaks to occur, ferret them all out before you try to tune the carbs
- Replace all o-rings in the carbs before you try tuning. Just like vacuum leaks add air where you don't want it, bad o-rings add fuel (and air) where you don't want it. That will ruin your tuning.
- Once you take stuff apart, don't put it back together until everything you can get to has been checked and fixed.
- 'Perfect' is probably too much to ask of a 25-year-old motorcycle with 21K miles, be willing to settle for "usable"
And finally, OWNING an old GS500 is a hobby in and of itself, separate from RIDING an old GS500
At the end of this little adventure I still have a bike that doesn't idle perfectly but it is at least usable. I'm not worried about it leaving me stranded or getting me into trouble.
Super psyched that you've made so much progress with this! Thanks for posting so many updates, I'm sure it will help people in the future if they ever have a similar problem.
Hopefully I can get my bike back on the road soon too lol.
For anyone who wants to follow a little more literary and less procedural description of this, check out http://joshkarnes.blogspot.com/2016/08/motorcycle-diary-pt-1.html
If you really dig reading some things I write, check out my books: http://joshkarnes.net/
That's all of the self-promotion I will do :)
Pretty interesting thread, you write well enough to keep your audience engaged. :D
I had a similar problem with my old Katana 600 which runs 4 of these annoying carbs instead of 2. As it turned out, after I'd done all the replacing of rubber parts (even the o-rings behind the rubber intakes) sealing every nook and cranny of the airbox, every o-ring in all 4 carbs (even the ones inside/under the needle jet holder...yep, there's one there too), turned out to be a poorly routed/adjusted throttle cable. Unless you lay eyes on the butterflys with the throttle fully closed, it's hard to tell where a fully closed throttle is. I ended up having to leave more play at the throttle tube than I like (in retrospect, I think the throttle tube should have been replaced) but just getting used to a different position of the right hand.
Anyway, on my GS I'm going methodically through the bike after I bought it from a PO who had a "friend" work on it for him. The carbs were assembled all wrong with missing o-rings and flopping float seats--a wonder the thing ran at all. Valve inspection and possible adjust is also being done after I remove all the over-tightend/seized bolts on the valve cover (actually have to drop the motor to get it done). Bottom line: never trust what a PO tells you, even if they are being sincere. Most of the time, they have no idea what they're talking about. The guy I bought my bike from for instance told me the carbs just need to be synchronized. Well I knew it was much more than that and told him as much since I was going to start with rebuilding the carbs and adjusting the valves THEN looking at carb synchronization. :thumb:
You're certainly right about the wrenching/riding ratio. You gotta enjoy them both if you own an old GS. Luckily, these old birds aren't too complicated. :cheers:
Good luck finding the hanging idle. What a pain! :sad:
Quote from: Arpee on September 10, 2016, 01:18:10 PM
Pretty interesting thread, you write well enough to keep your audience engaged. :D
Thanks! :) Fortunately the readers of this forum are already interested in the topic.
Quoteturned out to be a poorly routed/adjusted throttle cable.
I have double, triple, etc. checked mine, and even put what the factory manual recommends, 5-10mm of free play. I set the throttle with a fair amount (over 10mm) of free play and then adjusted it at the grip using the barrel adjuster. I
think I am in good shape here, but you never know.
Quote
Anyway, on my GS I'm going methodically through the bike after I bought it... Bottom line: never trust what a PO tells you, even if they are being sincere.
Right on!
Quote
Good luck finding the hanging idle. What a pain! :sad:
Actually I think I fixed the hanging idle, but I'm left with an annoying idle condition where if you set the idle to the correct speed when the engine is warm, then part of the time, maybe even most of the time, it will try to stall at idle by idling too low. But if you increase the idle at all, I mean even 1/10 or less of a turn on the idle adjust knob, it idles at 2K+ rpm. I am actually beginning to think this is due to the 40 pilot jets, and that with the 37.5s that the bike came with from the factory it might be able to be tuned to idle a little better. For example, you cannot set my bike to idle at 1500 rpm. It just won't. It will either go 2K+ or just touch the knob lower and it's 1100-1200. My guess is that once you open the butterflies
at all then it runs 2K rpms or more just because there's enough fuel at the pilot jet to run faster with the smallest amount of air you can get in past the throttles. With the throttles closed there is only enough air at the little bypass inlet whatever you call it to allow it to idle at under 1200 rpm. And due to some wear, poor state of tune, etc., mine won't idle consistently under 1200 rpm without trying to stall most of the time, so I have to constantly blip the throttle.
I just finished range day #1 of my MSF course and I have day #2 later today. I am doing the course on a Honda GROM. Now, first of all, talk about an easy bike to ride! And it's so unbelievably maneuverable. Anyway, I am rapidly getting hooked on how perfectly it runs (of course, these bikes are band new, less than 100 miles on them). Starts every time, idles absolutely perfectly all the time, can sit for 10 minutes straight at idle and just run without a hiccup, never hesitates or has to have the throttle bumped, etc. The GROMs are fuel injected while the other bikes (V-star 250s, an Eliminator and a DR200) all have carbs and they have that old school tendency to stall sometimes and you have to get the choke right and all that. I really like a lot of stuff about this GS but I'm telling you it's quite tempting to consider replacing it, promptly, with a fuel-injected Honda. And the tinkerer in me is working furiously on a plan to retrofit the CB500R's fuel injection to my GS :)
BTW, all... this is really good, if you can work around the occasional imprecise English:
http://members.ziggo.nl/minara/word%20bestanden%20website/Carburetor%20MIKUNI%20BST33.htm
And this looks like a winner!
http://stenhouseracing.com/shop/index.php?main_page=product_info&cPath=5_4&products_id=1
Kind of spendy, though. However, it sure would make adjusting those things way, way easier.
Learning that there are Aprilia, BMW, KTM and other Suzuki motorcycles (plus many more) bikes that share these Mikuni BST 33 carburetors really opens up the options on parts. Plus some of these owners are more technical or more likely tinkerers, and many have even replaced their carbs with NEW carbs, especially non-CV carbs. For those like me, who detest this carb design, this could be great. I mean, why spend so many hours rebuilding, tuning, etc. to get them close to right when you can flat out replace the entire carb with something brand new that will work perfectly from day one? And be easier to tune?
Quote from: mr72 on September 12, 2016, 09:22:58 AM
many have even replaced their carbs with NEW carbs, especially non-CV carbs. For those like me, who detest this carb design, this could be great. I mean, why spend so many hours rebuilding, tuning, etc. to get them close to right when you can flat out replace the entire carb with something brand new that will work perfectly from day one? And be easier to tune?
Here, here. The BST 33 wasn't too bad on its own on my DR350, but start lining them up in pairs and things get messy quick. The CV carb gets good gas milage and offers smooth response which is great on the street. That's about where the pro's end. The con's are as long as the arm, starting with fiddly air leaks and goof-ball petcocks...it goes on from there. Fuel injection is a welcome relief from all this.
Well, my problems persist.
Today I rode over to the gas station to fill it up (was on reserve to get there) and it died once at a stop sign, then wouldn't start again after filling it up. There's fuel all over the outside of the carbs and dripping onto the top of the crankcase from somewhere. My guess is it's flooding.
So, it's going to be back to the gas station with a trailer, bring it home and then tear the *@#$&$#%! carbs down AGAIN!!!
Out of frustration I bought a set of carbs from another forum member that I hope will be in better shape than the ones that came with this bike. Given the general condition, broken stuff, jury-rigged, holes filled that shouldn't be, epoxy on the carbs to fix (?) leaks, etc., I think these carbs may be a lost cause, best used for spare parts. The replacement pair is a cheap/quick fix.
However, in the long run, presuming a lot of factors like I can put a thousand miles on this bike over the next six months and I decide I am going to keep it for >1 year, I think I may spring for a pair of Mikuni VM32s and convert to something that requires less perfection to work. Considering I can buy VM32s brand new for $80-90 each, along with throttle cable and other misc. things I might need I think it may well be worth $200 to get brand new carbs on there that are not such a pain to tune.
Thanks for all the details. Following intently.
When it rains doesn't rain, it pours floods.
Well, I got the "new" carbs in, and they seem to be intact and in good shape, but for kicks I pulled the bowls and cleaned them, verified the float height and pulled the jets to verify the size (40/125). Gave it a cursory cleaning on the outside of the carbs, set the idle mixture screws to three turns out and mounted them on the bike.
Unfortunately I left it on prime and wound up with a cup or so of gasoline on the floor of the garage after leaving it sitting for a few hours. I suppose that answers the question of whether the float needles seat perfectly. Annnd... of course it wouldn't start. Which is wonderful.
I put the petcock back to Run and put it on the battery charger just in case, since I anticipate having to crank it it a lot to start it. But I am hopeful it will not only start, but it will idle correctly once I get a chance to try it this evening.
BTW I may have found the (another) cause of a lot of my problems with the old carbs, again quite by accident. See, when setting the float height on the "new" carbs, I noticed that the float needles don't constantly try to fall out. They are basically stuck in there, although I don't know exactly how firmly since I didn't try to remove them. On the old carbs, setting the float height is quite a challenge because the float needles fall out constantly when you tip the carb. Something tells me there must be some kind of o-ring or seal in the float needle valve holder that holds the float needle in place, and that part is missing or bad on my old carbs.
I seriously doubt that's the ONLY remaining problem on those old carbs, so they are best meant for the junk bin.
Like @rabies I too am following intently. This has been an epic journey and I have nothing but admiration for your tenacity.
Thanks for that.
Unfortunately my tenacity is going to have to go up a notch. The bike won't run with the new carbs. This is what it does now:
https://www.youtube.com/watch?v=MA9jmxpkeCk
Frustrating to say the least. My current quasi plan, at least until a person more intelligent or experienced than I advises me otherwise (likely in the other thread I started about this) is to pull the "new" carbs off, take them all the way apart, double freakin' check everything, replace the jets with the new ones from the other carbs (that were working, so I know they are not clogged), run a .015" guitar string through the pilot orifices, and transfer all of the new o-rings I can from the old carbs to the new.
My present theory is that the "new" carbs have clogged pilot jets which is why it won't start/run. Or the fuel orifice feeding the pilot circuit is clogged. Or something I have no idea to check is bad.
In general these replacement carbs are in far better condition than the others and in theory should work better eventually. They reportedly came off of a motorcycle that was running, at least much better than mine is now. I put 6 oz of Berryman's B12 in the tank, and I bet if I could get the thing to run a little while it'd start to clean itself out.
For the very little that it's worth, I agree with your theory. If the 'new' carbies have been sitting for a while with old fuel in them this could lead to clogged pilot jets.
Thinking 'happy thoughts' for you.
Disclaimer- Just trying to help with some ideas but I'm a noob so some of my ideas might sounds silly to the old hats! haha.
Hiya man, i'm still following your journey with this bike. I'm no ace mechanic by any stretch of the imagination or even knowledgeable (i usually just know enough to get myself in trouble lol) but I do like to tinker and do a lot of reading on subjects i'm interested in. Thought i'd toss out a few ideas for you to maybe check over. You say you think it's running rich and you run into most of your problems after the bike is warmed up? Have you checked the fuel pressure regulator? Ive read that they can cause hard starting and richness after the bike is warmed up when going bad . And that might account for why you can never seem to get the mix adjustment screw dialed in proper without it going wonky quickly after.
Also, you are thinking there might be a vacuum leak somewhere that you're having trouble nailing down, maybe you could try the smoke method of testing? I've seen a big 1000 dollar smoke machine tester that is used in shops, but i've also read about just using a cheap 99 cent cigar, puff away and blow it into an open line (or put a longer spare hose onto a point in the system to make it easier) and try to see where any smoke my be escaping. I'm not even sure if this would work in this application as i've never done it but it might be worth trying and i'd be interested to know if it works. Could also take a peek at the vacuum damper. I'm not sure if those are prone to go bad or not but it's something to look at if you can't nail down the vacuum leak and you're sure there is an issue with vacuum. Thanks for keeping us updated and I will continue to follow your thread till you prevail, and i'm sure you will! Good luck 72.
Quote from: SirHansford on September 22, 2016, 07:03:27 AM
Disclaimer- Just trying to help with some ideas but I'm a noob so some of my ideas might sounds silly to the old hats! haha.
Thanks for that. These ideas aren't silly but they may not all apply.
Quote
You say you think it's running rich and you run into most of your problems after the bike is warmed up?
Well, with the previous carbs I think I got the mixture fully sorted out, but the bike still would not idle consistently. Unknown why. Got sick of trying to work on those carbs which had unfixable potential problems, so I decided to change them to a "new" set that have yet-undiscovered, but maybe fewer and more fixable problems.
Quote
Have you checked the fuel pressure regulator?
No fuel pressure regulator, or fuel pump even, on most carb'd motorcycles. Certainly not on this one.
Quote
Also, you are thinking there might be a vacuum leak somewhere that you're having trouble nailing down,
That's not a bad suggestion if the "new" carbs seem to have a vacuum leak. The original carbs may have had vacuum or fuel leaks that I had not yet addressed, and I suspect maybe some that could not be repaired. If the "new" ones exhibit vacuum leak like symptoms (if I can ever get it to start!) then I'll try the smoke.
QuoteThanks for keeping us updated and I will continue to follow your thread till you prevail, and i'm sure you will! Good luck 72.
Mostly I just write here because I have nobody else to talk to about this stuff. Perhaps some knowledgeable folks will continue to chime in and help sort this out, and then later on others who may have similar problems with their quarter century old bike will have some info that might help them identify their problems.
Speaking of which, here's today's update:
I went out this morning to pull the carbs back off and inspect and clean some more. First alarming thing I found was that the right carb had no fuel in the bowl. Opened the drain screw, nothing came out. Once I got the carbs off, I pulled the bowl, no fuel. Dry as a bone. Why? Oh, because the float needle valve was literally stuck in the seat. That was likely a big part of my problem.
Also I discovered another alarming issue, my own fault. On the other carb, the spring in the top of the diaphragm was misaligned and would have caused the slide to never open, if the bike would ever have run enough to generate enough vacuum to try and pull up the slides. Fixed that.
And I discovered a crack in the vacuum hose going to the petcock. This is double bad since it would create a vacuum leak AND result in cutting the fuel supply. Fixed that.
I swapped in the known-good (not clogged) 40/127.5 jets from the other carbs (bike has equivalent of a "slip-on" exhaust, so bigger mains make a little bit of sense). Had a heck of a time getting the old pilot jets out of the "new" carbs. I didn't check (yet) if they were clogged. I also swapped the float needle seats (with new o-rings!) from the original carbs into the new, and ran a guitar string through the orifices to make sure they were not terribly clogged. Then I put everything back together. I did this whole entire job in less than an hour and had the bike ready to attempt starting.
And... well it wouldn't start. But I think that's because I had the petcock on "Run" instead of "Pri" ... if I put it on prime it may start. We shall see.
Also the overflow fuel hose was still attached to these carbs when I got them and I am reusing it, but it was pre-bent into a shape that wants to run below the airbox and down by the rear shock. Now, I may not be a physicist but I do think that if it does ever overflow that it will siphon constantly since the overflow hose runs below the carb bowl. I guess it hardly matters since there are more serious concerns if fuel comes out.
After work today, I'll see if it'll start. I still have a lot of idle speed setting and etc. to do. But as usual I am optimistic and hopeful it will eventually work. But I am coming close to my tolerance limit for working on this bike. I think if it doesn't start and run mostly correctly so I can ride it after this latest escapade, I might trailer it to a shop and hand over my wallet... or alternately I might go ahead and bite on that $200 worth of brand new VM32s and at least eliminate wear and tear from my list of concerns. I hate to admit it, but this is so annoying that I'm contemplating getting it limp-running enough to sell it, try and get most of my money back, and buy a FUEL INJECTED ER-6n instead. I don't mind having a cheap motorcycle that I occasionally have to tinker with, but I am beginning to be sick of having a cheap motorcycle that never will run and I only ever get to tinker with. I think I'd get a lot more riding enjoyment from one of those little GROMs from the MSF class! At least they would start and run every single time!
OK quick update:
I just had a few minutes, went out to start it up having put the carbs back in a way that might work and it started up and ran like a scalded cat. Revved itself to about 7,000 rpm until I turned down the idle, something like 3K, to let it warm up. I think I turned it down too low. I only ran it a couple of minutes in the garage and then tried turning off the choke and it died and won't start back yet but these are problems I know how to fix.
The awesome news though is this: NO HANGING IDLE!!! That's a tremendous improvement over before. And it revs and runs like crazy. I think it's very close to 'right'.
I truly think I just need to get the idle speed and mixture set correctly with it fully warmed up and it'll be good to go.
"new" carbs + new jets from old carbs + new o-rings + thorough carb cleaning/declogging = RUNS!!! I do realize I'm basically back to square one but before there were no other squares to advance to while this time I think I might actually get past 'Go'. There is hope. I'm putting away the explosives.
As they say at the football - "Played hard! Done good!" :thumb:
Hey Josh, just want to keep cheering you on!
Just finished my own GS project this summer, and took apart the carbs at least twice in the process. But totally worth it, it's such a fun bike to ride. With the tweaks I made, it runs about as well as my Yamaha R3 which is 10 years more modern.
A couple random suggestions:
- these bikes seem plagued by vacuum leaks. I removed the PAIR system; capped off the white plastic discs at the top of the carbs; switched the stock petcock with a simple on/off mechanical lever. Lots of threads on this forum about this process. The bike runs great with these modifications.
- make sure the slides bounce up and down easily without the least resistance. This was the cause of my hanging idle. I had oiled their surfaces in the mistaken belief that it would help the process, and only made things worse. Bone dry or a light spray with WD40 did the trick
- the bracket /slide plate that opens and closes the choke on the carbs can bind. I had to put in delrin washers on mine to get it aligned properly, so that it would slide easily back and forth. Before this, I really wasn't off choke when I thought I was, due to binding
- run the bike with the gas tank and air filter off (run a temporary fuel system with a funnel or turkey baster, but stay safe). This way you can check to see if the slides open and close correctly as you rev. Also check that your throttle cables are behaving.
Best of luck, and rock on!
Quote from: Endopotential on September 23, 2016, 12:15:29 AM
Hey Josh, just want to keep cheering you on!
Thanks!
Quote
Just finished my own GS project this summer, and took apart the carbs at least twice in the process.
Well I've had each pair of carbs apart at least twice already. One of these days it'll be the last time I
have to take the apart to get the bike to run!
Quote
- these bikes seem plagued by vacuum leaks. ...
No kidding. I think I have chased them down on this bike, who knows about the "new" carbs. Mine ('92) doesn't have PAIR. My history of leaving the petcock on prime seems to indicate I should try and stick with the vacuum petcock for the time being. But I wouldn't mind if it had an "OFF" manual setting.
Quote
- make sure the slides bounce up and down easily ...
They do with the carbs off the bike. Haven't looked with it running.
Quote
- the bracket /slide plate that opens and closes the choke on the carbs can bind. I had to put in delrin washers on mine to get it aligned properly, so that it would slide easily back and forth.
I wondered about that. Seems like a rather imprecise assembly. I wonder if that was not one of my problems with the original carbs.
Quote
- run the bike with the gas tank and air filter off (run a temporary fuel system with a funnel or turkey baster, but stay safe).
Yeah next time I have the tank off, I'll have to give this a shot. I really am hoping to not have to deal with this for a while.
I mean, truth is, I just want this bike to run so I can go ride it some and make a meaningful decision on whether I keep it for a long time and do the mechanical and cosmetic work it would need to be a long-term addition to my home, or whether it's not the bike for me and I flip it and buy something else (with fuel injection!).
Update:
Friday I started it up and rode down my steep driveway and it died on the street. It was surging when aimed downhill which was strange to say the least. It wouldn't start again, so I left it sitting overnight on the street. It's too heavy to push back up my driveway.
Saturday morning I went out and pulled the carbs again. I have got this down to a science, let me tell you. There was liquid gas in the intake boots and one plug was wet with gas even after sitting overnight. I re-checked the float height and it looks like for whatever reason I really had myself fooled before. The floats were too high so I adjusted them and for good measure I put the float needles from the original carbs into the "new" ones. They all looked to be in just fine shape but the "new" carb had one float needle sticking and I didn't want to risk it.
Now, putting it back together, I discovered something. Anyone else get annoyed putting the stock airbox on? Well I think I have that licked. First of all, I used some "General Purpose Cement" from Harbor Freight to glue the airbox boots in place, since they kept popping out of their hole when I wrestled with it before. Any decent rubber-based cement will work, but this sub-$1 stuff works perfectly. Now when you go to put the airbox in, first get the fuel petcock and hoses completely out of the way. Then put the REAR of the airbox in first, with it tilted like 60 degrees. It will slide right in to its spot. Then with the air filter out, put a hand inside the airbox and manipulate the boots over the carb throats from the inside. Just like that, I had the airbox in there in like 30 seconds this way. The real key is gluing in the boots, and then knowing to put the rear of the airbox in first with it tilted.
Once I had it all together I noticed visible "junk" in the reserve fuel hose. I pulled it loose from the petcock and drained it. Didn't want that "junk" in the carbs! Then I tried to start it and it wouldn't fire. Figured out eventually that the tank petcock was turned just a little bit PAST vertical, which results in restricted or no fuel flow. You know it will turn like 110 degrees, but you need it at 90 degrees for it to flow. Lovely. Once I got THAT sorted, I started it up and it ran just like it was supposed to for long enough for me to notice it dripping fuel from one of the fuel hoses. Turned it off and then tightened the snot out of the tank hose clamps. Now no leaks. Petcock in the right place. Everything together. Started it up and voila! It fired right up, revved itself to 5K rpms, and it works pretty well. Well enough for me to ride it up into my garage.
This morning I decided to go out and fiddle with the idle mixture and idle speed on the "new" carbs. I wound up with 3.5 turns out and I still think it may be a little lean. I rode it about 5 miles until it started raining, and set the idle to about 1500 rpm with it hot.
I still think it needs idle tuning, but I also think it CAN be made to run right now.
It has a little stumble coming off idle and I think that's because it's lean. It has a little hanging idle, again likely lean. But that I can fix.
Other good news is that it seems to be capable of starting while the engine is hot. Getting closer to a usable motorcycle here. I thought the day may never come.
If we didn't have thunderstorms in the forecast all afternoon and evening I'd be out riding it now.
Next time you have the carbs off, pull the jets and with compressed air, blow air in every frigging hole under the bowls :thumb:
Topic: Idle troubles: Maybe pull the idle mixture screws too and blow some compressed air in there, also any small holes in the bores/carb body's, don't blow any air in the large ports on top, those ports supply vacuum for the slides.....they are not potentially clogged like the small holes in the body's might be.
That's great to hear!
Sent from my iPhone using Tapatalk
Quote from: Suzuki Stevo on September 25, 2016, 04:48:24 PM
Next time you have the carbs off, pull the jets and with compressed air, blow air in every frigging hole under the bowls :thumb:
Topic: Idle troubles: Maybe pull the idle mixture screws too and blow some compressed air in there, also any small holes in the bores/carb body's, don't blow any air in the large ports on top, those ports supply vacuum for the slides.....they are not potentially clogged like the small holes in the body's might be.
Funny. I actually thought of doing exactly that when they were off, but my air compressor was also broken. So I used a .013" guitar string to run through every orifice. Then I got the valve rebuild kit for my air compressor in the mail later Saturday and repaired it. So next time, I'm golden!
Here's hoping there's not a next time for me to have the carbs off. At least not in 2016! Chances are slim, I know.
Question: what affects idle speed more, the mixture or the idle speed screw? I am still having the issue I had with the previous carbs where it will idle at like 2.5-3K rpm and then if I turn the idle screw just like 1/16 of turn, it goes down to like 900. Does this indicate an idle mixture problem or something else?
It's funny it is doing basically the same thing with the second set of carbs which makes me also think I need to get serious about checking the valve clearances.
Alright. My dislike for this thing is increasing.
Yesterday I had a few minutes and given the gorgeous weather we are supposed to have here for the next week I figured I need to get the bike working so I can go ride it with my dad this weekend. BTW, lest any of you think by saying "my dad" all the time I'm some kid, well I'm not. My dad just turned 65 and I'm 43. Riding motorcycles in a leisurely fashion is something he wants to do to enjoy his pre-retirement spare time, and it's pretty much the whole reason I bought a motorcycle.
So I went out and rode around the neighborhood a bit just to a) get the bike warmed up enough to set the idle and b) build my confidence that the ol' GS is not going to strand me at a stop sign.
Good news is that it started right up and ran like it is supposed to when it was stone cold. I went ahead and started riding with part choke on and then turned off the choke completely after about 5 minutes. Bike was a little stumbly coming off low/idle revs at initial throttle opening which I now realize may very well be caused by a vacuum leak (did I mention I hate these carbs?). But overall, it ran just pretty great. After riding for about 10 minutes I decided to try setting the idle. I set it lower than it was (it was hovering around 3K) down to under 2K but I didn't want to go too far and have it stall at a stop sign. Eventually after riding for about 20-30 minutes I returned home and tinkered with the mixture a tad trying to get it to idle.
I was still not able to get it to idle correctly.I can set it to idle at about 2K rpms but if I try to drop it any more, it idles below 1K and stalls if I don't keep bumping the throttle. And it's very sluggish coming off "idle" when it is trying to idle at whatever 500 rpm that it is trying to do.
So, I went ahead and pulled it into the garage where it predictably stalled (it's never made it into my garage without dying). The frikin' thing WOULD NOT START again. So it won't start while hot. I tried with some choke, all choke, no choke, it just won't start.
And this is exactly where I started. Only now I have different carburetors and I have spent probably 20 hours working on this blasted thing. It will idle either at 2K+ or it will die, and it will not start when hot.
Someone posted a 2007 GS500F with under 3K miles on it on the local CL for $1K and I am incredibly tempted to just go buy it, drop the money into the F-E conversion and sell old red. Give up. I hate to consider that since even though the 2007 is much newer it is far more complicated to work on and I have no love for the fairings or appearance. But I just need something that will run reliably and I am beginning to think this old klunker won't ever do that.
Anyway, back on to the issues. As I was getting off of the bike, contemplating what might have gone wrong, I noticed an alarming sight. One of the tiny little washers that goes on the idle mixture needle was laying on my workbench. That means it wasn't in the carb! Maybe that explains why one of the carbs did not seem to be responding to mixture changes. And that might be the whole problem.
Can any of you confirm that this washer missing may cause poor idle AND not starting while hot?Later last night I pulled the needle screw and for sure, the unresponsive carb had no washer. I managed to plug the o-ring out with a toothpick and it was also rather flat but seemed kind of OK. I had a spare so I replaced it. For good measure I pulled the needle from the other carb and it had the washer, but I was not able to get any o-ring to come out of the hole (I didn't pull the carbs). Maybe there's one stuck in there, who knows. Maybe it got lost while I had the carbs torn down, like the washer for the other carb. So I put the mildly flattened o-ring from the other carb in there just in case, figuring two flattened o-rings is probably not a disaster but I'll order new ones for both sides anyway. I re-adjusted to 3 turns out AGAIN and I'll try my tuning exercise AGAIN today after work.
I seriously need solid advice on why the bike won't start when hot. And this is not some kind of electrical problem. The starter turns just fine. It occasionally tries to fire. It kind of behaves like it's flooded to some degree, but I didn't pull the plugs to see if they are fouled. I figure it could be one of the following:
- Missing o-rings and washers on idle mixture needles caused erratic fuel delivery and it's super rich at idle, flooding. Why then would it start when cold? Are the plugs just drying?
- Missing o-rings and washers on idle mixture needles caused vacuum leak which screwed up my idle stability as well as prevents starting, but why only when hot? Maybe because the choke fixes this when cold, but when it's hot the choke makes it too rich?
- Some other undiagnosed problem is causing everything wrong... maybe it won't idle under 2K rpm because the igniter is not working correctly on 12V battery voltage and only has enough juice when running on the alternator's voltage but it only acts like this when it is hot. Maybe tight exhaust valves are causing the poor idle and no-start because of no compression at low rpms but the clearance is bigger when hot and when cold compression is fine. Maybe it's something I am too inexperienced to contemplate.
- Maybe I need a whole different motorcycle.
So should I buy the '07 F and give up on the '92? I only paid $1K for the '92 and it's in better shape now than it was when I bought it. I could definitely get my money back out of it. And $100 in lights and brackets turns the F into an E. Starting to think that's the way better bet.
No point doing anything if the valves are not in spec, If the carbs are stock.
I've owned many of these bikes and when the exhaust valves are really tight, the bike has trouble idling even when fully warm and hard to start. If a little tight, it will run okay when warm.
Quote from: HPP8140 on September 28, 2016, 09:52:45 AM
No point doing anything if the valves are not in spec, If the carbs are stock.
I've owned many of these bikes and when the exhaust valves are really tight, the bike has trouble idling even when fully warm and hard to start. If a little tight, it will run okay when warm.
Yeah but I am having the opposite problem, if I am reading you correctly. Mine starts and runs great when cold and has a 1000-rpm wide hole where it won't run between 1K and 2K rpm where the idle speed jumps when it's hot, and it won't start at all when hot. It's not hard to start when cold, just impossible to start when hot.
IME (with cars ... Miata specifically) a tight valve makes it run rough when cold and one it warms up the alloy head expands more than the valve hardware (valve stem, bucket, shim, cam) and the valve closes fine, runs smooth when hot. I am having opposite issues here.
I'm hopeful that my missing washer and maybe missing o-ring were the root cause of my issue, but I have my doubts. Thinking about it, that o-ring doesn't make much sense because what does it seal on the screw side? A washer? I guess it's possible it seals against the neck of the needle and on the outside against the body of the carb and the washer and spring just keep it in place, but it's weird. I wonder if the bike would run a lot better with a factory-style brass cap pressed back over the idle screws after adjusting ... or even just a rubber plug. What is the leak here anyway? grr.. I need a diagram of fuel and air flow for this carb.
Quote from: mr72 on September 28, 2016, 07:18:00 AM
...
Someone posted a 2007 GS500F with under 3K miles on it on the local CL for $1K and I am incredibly tempted to just go buy it, drop the money into the F-E conversion and sell old red. Give up. I hate to consider that since even though the 2007 is much newer it is far more complicated to work on and I have no love for the fairings or appearance. But I just need something that will run reliably and I am beginning to think this old klunker won't ever do that.
...
So should I buy the '07 F and give up on the '92? I only paid $1K for the '92 and it's in better shape now than it was when I bought it. I could definitely get my money back out of it. And $100 in lights and brackets turns the F into an E. Starting to think that's the way better bet.
The 07 F is not really "far more complicated". Is basically the same bike, with the same engine, except with an oil cooler. And like you said, its extremely easy to just turn it into an E body type. So, if you think you can basically break even on your current bike and buy the more reliable, newer one then that definitely a viable option.
If you do end up buying the F, you can sell the fairings for a couple hundred bucks if they're in good shape.
Quote from: mr72 on September 28, 2016, 10:19:09 AM
Quote from: HPP8140 on September 28, 2016, 09:52:45 AM
No point doing anything if the valves are not in spec, If the carbs are stock.
I've owned many of these bikes and when the exhaust valves are really tight, the bike has trouble idling even when fully warm and hard to start. If a little tight, it will run okay when warm.
Yeah but I am having the opposite problem, if I am reading you correctly. Mine starts and runs great when cold and has a 1000-rpm wide hole where it won't run between 1K and 2K rpm where the idle speed jumps when it's hot, and it won't start at all when hot. It's not hard to start when cold, just impossible to start when hot.
IME (with cars ... Miata specifically) a tight valve makes it run rough when cold and one it warms up the alloy head expands more than the valve hardware (valve stem, bucket, shim, cam) and the valve closes fine, runs smooth when hot. I am having opposite issues here.
I'm hopeful that my missing washer and maybe missing o-ring were the root cause of my issue, but I have my doubts. Thinking about it, that o-ring doesn't make much sense because what does it seal on the screw side? A washer? I guess it's possible it seals against the neck of the needle and on the outside against the body of the carb and the washer and spring just keep it in place, but it's weird. I wonder if the bike would run a lot better with a factory-style brass cap pressed back over the idle screws after adjusting ... or even just a rubber plug. What is the leak here anyway? grr.. I need a diagram of fuel and air flow for this carb.
Okay, did not read entire thread.
Quote from: qcbaker on September 28, 2016, 11:18:45 AM
The 07 F is not really "far more complicated". Is basically the same bike, with the same engine, except with an oil cooler. And like you said, its extremely easy to just turn it into an E body type. So, if you think you can basically break even on your current bike and buy the more reliable, newer one then that definitely a viable option.
If you do end up buying the F, you can sell the fairings for a couple hundred bucks if they're in good shape.
From what I have read, it looks like the '07s have noticeably more complicated carbs. Dunno when they switched. It's not just the carbs but it's sensors etc. But this bike is reportedly reliable and running right today.
The fairings on it are mint as far as I can tell from the pictures. But the seller has not gotten back to me, my guess is it's gone. If I hear back, I think I'm just going to go buy it.
Well, it wouldn't start today. I finally ran the battery low enough that it was guaranteed to not start. It's on the charger now. It may start and run again with minimal tinkering, who knows.
I have an appointment to look at the '07 GS500F tomorrow. I am pretty much ready to give up on the '92. We'll see how it goes. I may have taken my farewell ride on the '92. I will have only ridden less than 20 miles on it total if I sell it, that's in about 2 months.
wow, $1000 for a 2007 with under 3k? that's pretty darn amazing for price granted it doesn't have a country of gremlins living on it. I paid 2000 for my 2007 with 5k miles on it and the bike KBBs for 2450, so yeah, if the bike runs well, doesn't make a bunch of noise and passes a good thorough inspection, i'd be all over that. at that price, i'd buy it just to have a 2nd bike and a parts bike should one go down. good luck man
I hate to say it, but I'd go with the '07. I bought an '09 in Feb. for $1,700, and thought I was getting a pretty good deal. I'm probably up to $2,000 into it, and it's finally running the way it should...if only it would quit raining.
I admire your efforts, but if you think you can get your money back out of the '92 (which you probably can), buying the newer bike is probably the way to go. I know there are some differences starting with the '04 models, but I don't think the newer ones are much more complicated than the older models.
FWIW, I went out today and tried to start it, and it won't start. I take that back, it will occasionally start with WOT, and it runs at like 400 rpm with WOT and then dies after 5 seconds. Then it won't start for a long time.
While it is trying to start, it backfires every so often, sometimes through the intake, sometimes exhaust.
Left plug came out wet with gas. After 5-second of bad running the right plug came out black.
Sounds like left carb is super rich and right carb is just somewhat rich.
Anyway, this has officially used up the last of my patience. Basically if I am going to have to put more time and money into a motorcycle, it's not going to be one that's 25 years old with 21K miles and a ton of issues. I'll start with a cleaner slate, better candidate for freshening.
EDIT---->
Somehow by a ridiculous miracle of fate I just fixed it.
It was one too many o-rings on one of the pilot needle adjusters. I pulled the needle, just to check, fuel dumped out the hole. Picked out the superfluous o-ring (one is apparently buried in there), and then put the needle back. Adjusted both carbs to 2.5 turns out. Cranked it with the throttle open to clear the flooding. It started, then after holding the throttle for about 3 seconds it started ripping up in revs and it idled at 4.5K, up to 5K with choke, even rolled down my steep driveway without surging. Turned off the choke and it wanted to idle at 3K, adjusted it down a bit, rode around my 3 mile loop a few times, adjusted the idle back down to under 2K with no issues when I got back.
And for the first time I rode up the driveway and into the garage without it dying at the top.
Turned it off and restarted it easily with the engine hot. In case I was going nuts I did it again, turned off and restarted, no sweat.
It still has a hair of a hanging idle so it probably is still a touch lean but man, how nuts that the thing actually runs.
I'm still going to look at the '07, leaving in like 5 minutes. I still will likely buy it and sell the '92, but at least I will be selling a RUNNING GS500E! Or if the '07 doesn't work out then I'll have something that works.
Dang. That was weird.
Quote from: mr72 on September 29, 2016, 11:12:18 AM
FWIW, I went out today and tried to start it, and it won't start. I take that back, it will occasionally start with WOT, and it runs at like 400 rpm with WOT and then dies after 5 seconds. Then it won't start for a long time.
While it is trying to start, it backfires every so often, sometimes through the intake, sometimes exhaust.
Left plug came out wet with gas. After 5-second of bad running the right plug came out black.
Sounds like left carb is super rich and right carb is just somewhat rich.
Anyway, this has officially used up the last of my patience. Basically if I am going to have to put more time and money into a motorcycle, it's not going to be one that's 25 years old with 21K miles and a ton of issues. I'll start with a cleaner slate, better candidate for freshening.
EDIT---->
Somehow by a ridiculous miracle of fate I just fixed it.
It was one too many o-rings on one of the pilot needle adjusters. I pulled the needle, just to check, fuel dumped out the hole. Picked out the superfluous o-ring (one is apparently buried in there), and then put the needle back. Adjusted both carbs to 2.5 turns out. Cranked it with the throttle open to clear the flooding. It started, then after holding the throttle for about 3 seconds it started ripping up in revs and it idled at 4.5K, up to 5K with choke, even rolled down my steep driveway without surging. Turned off the choke and it wanted to idle at 3K, adjusted it down a bit, rode around my 3 mile loop a few times, adjusted the idle back down to under 2K with no issues when I got back.
And for the first time I rode up the driveway and into the garage without it dying at the top.
Turned it off and restarted it easily with the engine hot. In case I was going nuts I did it again, turned off and restarted, no sweat.
It still has a hair of a hanging idle so it probably is still a touch lean but man, how nuts that the thing actually runs.
I'm still going to look at the '07, leaving in like 5 minutes. I still will likely buy it and sell the '92, but at least I will be selling a RUNNING GS500E! Or if the '07 doesn't work out then I'll have something that works.
Dang. That was weird.
Great to hear that you fixed it, finally! :woohoo:
Why buy the 07 if you got yours running correctly now?
I went and looked at the '07. It was in pieces when we got there to look at it. After half an hour of helping the owner try to get the battery connected etc. we finally jump started it from my Jeep and it refused to idle and died constantly. Basically mechanically no better than the bike I have, and frankly for a 9 year old bike with only 3K miles on it, it was in no better shape than my old one. Dents, laid down several times on both sides, you name it.
I made a low-ball offer, they balked, I passed.
So then, I came home and my old '92 started right up. We hung around and let it run for a few minutes until it was partly warmed up, turn off, then it started right back again. No sweat. Half an hour later I went out and fired it right up, rode it for 20 minutes, worked like a champ, did a little more fine adjusting of the idle, and when I got home it was idling perfectly at 1300-1500 rpm or so and then restarted when it was hot.
I think I have the gremlins tamed for the time being.
So, the old girl came through. She didn't want to get tossed for a newer model. I think she's got the potential to be a keeper. She's sure putting on a good show this afternoon.
My dad wants me to do a ride with him this weekend into the back roads to a little town about 20 miles away or so, so this will be a big excursion. I think the GS will do it.
Man. Talk about a big 180. My old bike must be reading this forum.
:woohoo: for the '92 !!!
Congrats mr72 :star:
Indeed :woohoo: !!!
Mate, that's excellent news.
Reaffirms my faith in tenacity.
Just adding on here. There are actually some things I learned in this process and I realized that I mostly came here to the forum to describe symptoms and ask for help, but I didn't mention what I learned that worked.
So just a quick recap, for those in the future who may stumble upon this thread with similar problems of their own.
With the original carbs, there was an array of problems that caused my original symptoms. It's hard to track down exactly what caused what since the behavior was very erratic, but here's what I found:
- "little o-rings" that seal the vacuum ports were missing -- this causes a major vacuum leak
- vacuum ports were broken off and improperly sealed -- even with new "little o-rings" this caused a major vacuum leak
- intake boots o-rings were hard, brittle and flat -- this caused a major vacuum leak
- float o-rings were shot -- this caused a major fuel leak into the carb bowls and inconsistent float level
- float needle seat o-rings also shot -- further causing a major fuel leak and bad float level
- pilot/idle needle o-rings were bad, which caused inability to correctly idle or set idle mixture even when other things were fixed
- some other undiagnosed problems on the carbs prompted me to replace them -- most likely more vacuum leaks and whatever o-rings I did not change were bad
All in all, these carbs were just done in. That's the long and short of it. One could potentially rebuild and nurse them back to health but it wouldn't be worth it.
I bought a set of replacement [used] carbs and then proceeded to make mistakes in addition to other issues that led to recurrence of similar symptoms. Here's the run-down.
- replacement carbs had been sitting and had misc. corrosion and clogs, most of which I cleaned and cleared before first installation. After I installed them the first time, I discovered the pilot jets were still clogged and the float level was wrong, so I replaced both jets in both carbs and adjusted the float height twice.
- most o-rings were in pretty good shape but I replaced them anyway.
- one of the float needles was sticking so I put the float needles and seats from the original carbs into the replacements
- first installation indicated I still had a vacuum leak, it was a crack in the petcock vacuum hose.
- due to my OCD about the pilot mixture needles' potentially bad o-rings, I removed them to inspect, finding they were in good shape, I put it back together but left out one of the washers. The bike ran right one time when it was put together this way but the carb on that side didn't seem to respond to any idle mixture adjustment. Then it would not start again.
- when I fixed the missing washer on the pilot needle, my OCD about o-rings kicked in again and I replaced the o-ring on that needle while it was out. Then for good measure I checked the other carb to ensure that the washer and o-ring were on that needle. The washer was there but I couldn't get an o-ring to come out with the carbs still on the bike, and I wrongly assumed it was missing so I added one and put it together. After this, the bike wouldn't start. The carb with the extra o-ring on the needle valve was flooding.
- when I removed the extra o-ring from the pilot needle that apparently had two on it and put it back together, the bike runs perfectly. If I had left the pilot needles alone on the replacement carbs rather than checking them and introducing my own mistakes, it would have worked fine from the start
I learned a ton about vacuum leaks and the pilot screws when working on this, and I'll post new threads on that. I just wanted to tie this one up.
Congrats! Glad to hear you've got it all worked out.
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Congrats 72! Really happy to hear ya tracked down that gremlin man. I'm sure you were ready to pull your hair out, but boy oh boy, now you know that vacuum system and the carbs like the back of your hand having pulled them apart so much. I would take that as a win win as you walk away from this a much more experienced owner who'll have no fear whatsoever taking on any issue you might run across in the future. * HIGH FIVE *
Thanks guys. I'm pretty pleased with how this all turned out. It wasn't what I expected or what I wanted, but in the end, like you say, I racked up a lot of quick experience and also built up some confidence not only that I know how to handle issues with the GS, but also confidence that I know the bike inside and out.