Okay, I'm about to give up. I just don't understand. My bike is showing all the symptoms of running lean due to poor fuel flow. It runs fine for a bit, starts sputtering at speed, and both spark plugs are white.
I figured that it was a constriction in the fuel lines. I checked. The flow seems sufficient. I thought that maybe it was a problem with the float valves. Nope. The carbs were cleaned out right before christmas to try and fix this, and I cleaned out the jets before I rode it last weekend to try and diagnose it. I even took videos of the fuel flow out of each carburetor with my phone. The videos work in quicktime, but I don't know what else they work with if you don't have it.
Video 1 (right carb) (http://devils.eng.fsu.edu/~rhunter/gs500/MOV00002.3gp)
Video 2 (left carb) (http://devils.eng.fsu.edu/~rhunter/gs500/MOV00003.3gp)
I mention in the video that I thought the flow out of the left carb is less. I now disagree with that assessment. Oh, and I have a cold, and I sound like it.
Isn't there a screen or a filter in the stock petcock? I thought I remember someone taking it apart and cleaning it.... Vacuummmmmmmmmm leak? Not pulling enuff vaccuummmmmm?
If it was clogged, there wouldn't be enough fuel flow.
Switching the petcock to PRI doesn't help the situation, so it's not a vacuum problem.
Hey Eg, hope you're not selling the bike, oh yea my neighbor doesn't have the money to buy it. He never did.
GL finding out why it's lean. :thumb: :thumb:
try backing the fuel mixture screws out a half turn.
I went through this and finding out why mine was rich. Turned out the mixture screws were out way too far.
I4
The question is, do you guys think the fuel flow is insufficient? That's kinda' why I took the videos. :icon_mrgreen: I think it's fine, but I may be wrong.
I will check all your suggestions when I get home from work assuming it doesn't rain today like they're say it might. I'm also going to remove the fuel filter to check whether it is clogged.
Edit: And yeah, tussey, my bike's still for sale, but I'm going to at least try to ride it before it goes away. And I'd hate to be that bastard PO who gave someone a bike that wasn't running right.
I4
could it be somthing with valve adjustment. where the engine is bringing in to much air for the amount of fuel? what exhuast are you running? I had a problem with my car one time that was like this. no matter what engine I swapped in it (3 to be exhuast USDM and JDM) it always ran lean ,,, too lean . needless to the say all three engines bit the dust and I couldnt ever figure it out. Untill I figured out what they all had in common. the header on the motor, it wasnt properly designed and I was hard on the car My father can explain it to me again, I'm no engineer but it was causing major problems with the engine.
its just an idea. I could be way off but I thought I would share.
How fast the fuel flows out of the carb bowl drain has nothing to do with how fast the carb bowls fill.
It does after a while. It can only flow as fast as it can fill.
Edit: I reread my post, and yeah, it does seem like that's what I'm saying, but believe me, I let that thing run for several minutes. I got at least a pint of gas out of one carburetor before deciding that the flow wasn't going to slow down, so it's running into the carb at least that fast.
Yay! Good weather and a day off so an update:
I've done some experimenting this morning. The petcock and fuel filter do restrict the fuel flow significantly. So to eliminate that possibility. I ran a line directly from the reserve to the carburetor and plugged the other line. No change, and that flow will drain the tank in minutes, so we know that's not the problem. It flows constantly, and the problem manifests itself almost immediately, so there's no vacuum forming in the tank,
The next experiment, I unhooked one cylinder at a time to see how each is running individually. Running on the left cylinder, it backfires significantly, but otherwise it runs okay.
Running on the right cylinder, there was no backfiring, but that could be because it was run first, and the left exhaust wasn't hot. However, this cylinder was the one giving me the problems. It's missing fairly severly on that cylinder. It's causing the jerkiness that I feel when riding.
The fuel level in the carbs is even with the float bowl gasket on the right, and about 2 mm above on the left.
That's all I've checked so far. Next on the list is checking the timing (unlikely but easy), the mixture screws, adjusting the right fuel level up a bit.
The timing is fine. I adjusted the right fuel level to be very close to level with the left. I checked the right carb jets, and they're clean as a whistle. The mixture screws were both 3 turns out, which is what I've been running since I got the bike.
So how much money did you put on it? :icon_mrgreen:
Really important question.....
is it running lean at idle... or half throttle..... or WFO.....?
it sounds like at idle only......
what size idle jets are in there?
do a compression test.....just cause I asked
sync the carbs also......same reason as above
and 1/4 turn more open on your air bleed screws
re read first post....
what size mains also?
stock air box?
stock pipe?
werase643: Read my signature for most of your questions.
Correction on the problem description. Rerunning my test last night with each cylinder, the right's running fine, and the left is running badly.
I think I may have found the problem though. I got so excited that I didn't fix it yet. The part of the float with the o-ring has a passage that's supposed to be open. It's clogged. It might not be drawing fuel fast enough in that one. I'm going go clear it out and go for a test ride if the rain doesn't hit first.
Compression was checked as one of the first things, sorry. The cylinder that's running right has worse compression than the one that's running badly, but they're both within spec. Don't remember the exact numbers ATM.
The carbs were synced. I thought that was initially the problem. I'll adjust the screws if I don't fix it, but 3 turns worked for several months.
i was going to ask about the o-ring around the float needle seat, next
the right is trying to do more work to compensate for the left
after you clean/fix....probably have to resync the carbs to get the cylinders pulling air in together
Well, I put it together and started it before the rain hit. It looks like it's going to get bad soon on the radar, so I'll wait until afterward to test ride and resync the carbs. When I started it, it didn't seem to be missing anymore, so hopefully that's done it. I'll let y'all know.
So I caught a break in the rain, and took it for a spin. The purpose was to warm it up for rebalancing since I'd had the carbs apart and cleaned that bit of gunk out, but I couldn't help but notice that the symptoms were the same, or worse. I had to keep reminding myself not to panic.
So I got it home, balanced the carbs, and went back out before the serious rain got here. It runs great. Doesn't miss a lick. Just in time for the rain.
Quote from: Egaeus on February 25, 2007, 12:05:55 PM
So I caught a break in the rain, and took it for a spin. The purpose was to warm it up for rebalancing since I'd had the carbs apart and cleaned that bit of gunk out, but I couldn't help but notice that the symptoms were the same, or worse. I had to keep reminding myself not to panic.
So I got it home, balanced the carbs, and went back out before the serious rain got here. It runs great. Doesn't miss a lick. Just in time for the rain.
So you fixed it? Clogged carb hole? Badass Eg, good troubleshooting!! :thumb: :thumb: :thumb: :bowdown: :bowdown:
Quote from: Egaeus on February 25, 2007, 12:05:55 PM
So I caught a break in the rain, and took it for a spin. The purpose was to warm it up for rebalancing since I'd had the carbs apart and cleaned that bit of gunk out, but I couldn't help but notice that the symptoms were the same, or worse. I had to keep reminding myself not to panic.
So I got it home, balanced the carbs, and went back out before the serious rain got here. It runs great. Doesn't miss a lick. Just in time for the rain.
Great job!
I always wander to resync carbs and do all this job, do you have to disassable the bike to take carbs out for each tiny little adjustment or is there another way to do that?
To synchronize the carbs you have to take the frame covers loose, and take the seat and tank off. I take the frame covers off, but you don't have to. It is done while running, so you need to hook the tank up at about the same height so that fuel will flow. I will post a short, small video that I took yesterday of my carb balancer in use that I took in anticipation of my bike not running right. I didn't need to post it for that, but I will do so when I get home.
Okay, so cleaning out the choke didn't fix the problem. Between rain, darkness, cold, and going out of town, I finally got around to putting the bike completely back together, and I rode for a bit and it starting having the same symptoms after a few miles. It's running sporadically on one cylinder, and backfiring out of the exhaust again.
Funny thing is that now, since the choke is working 100%, it actually has an effect on the bike. When I pull back the choke, the bike starts running correctly. The missing goes away, and the backfiring stops. Switching to PRI has no effect. When I am idling warm, without choke I idle at a normal speed, but with choke it goes up to ~5000 rpm.
So the jets are as clean as new, the emulsion tubes are clear, and the fuel level in both carbs is at the correct height. I'm at a loss. I'm thinking vacuum leak, but where? The boots are flexible and the clamps are tight and the frame petcock is working fine, so where could it be leaking?
A quick shot of starting fluid at the boots while running will tell ya, if she speeds up, that's it.
You need to prove some things beyond reasonable doubt first....
Float level needs to be seen at the exact point in time of the problem occuring. You need to connect some clear tubing to the float drain stub, open the screw and bend the tube upwards above the carb. The fuel will level off in the clear tubing to show the float level in the carb at ANY time!
If you want to set up the tubes properly you can use right angled tube connectors to go around the carb. I use pet store aquarium pump connectors, they seem to be petrol proof! The tubing should be proper clear fuel line if you can get it, otherwise expect it to melt after 5 minutes. Don't use silicon rubber tubing, it melts!
MAKE SURE THIS TUBING IS SECURE!
Run the bike on 'prime'. When the problem happens, very quickly switch to 'on' and kill the engine. Then check the float level. If it's ok you can rule it out. Be careful that the tubes don't fall off or move or fuel will go everywhere and torch your bike and yourself.
Your 'choke effect' can be VERY misleading!! There could be many causes to this fault.
Okay, so I got some starting fluid and rode the bike to work so it'd be warm when I got home to work on it. I took videos. I also got some clear weed eater fuel line so I can check the fuel level while running (the aquarium line's ID is too large, it falls off). I will do the fuel level test later, but I went ahead and checked for vacuum leaks. I, however, am a dumbass. See the video....
The videos
Balanced carbs on the 25th (http://devils.eng.fsu.edu/~rhunter/gs500/CarbsBalanced.3gp)
Still balanced today (http://devils.eng.fsu.edu/~rhunter/gs500/CarbsStillBalanced.3gp)
I check for vacuum leaks (http://devils.eng.fsu.edu/~rhunter/gs500/VacuumLeakTest.3gp)
f%$k! I'm a dumbass (http://devils.eng.fsu.edu/~rhunter/gs500/OhCrap.3gp)
That's okay, I never throw things away (http://devils.eng.fsu.edu/~rhunter/gs500/NowWeWait.3gp)
So if you have any ideas as to why the starting fluid caused my right cylinder to quit running instead of the predicted behavior, I'd be interested in hearing them. Obviously, the rest will have to wait until tomorrow....
Okay, the vacuum leak is fixed. It was a vacuum leak. I still don't know why it caused the cylinder to quit running, but anyway....
It's running worse now, believe it or not. It's still sputtering and backfiring out of the exhaust.
I'm willing to believe that the vacuum leak out of the top cover would cause a problem during normal operation. However, when balancing the carbs, the aquarium line is much tighter than the cap that's on there. The carbs should be balanced.
I ran it on one cylinder at a time again. It's having the same problems on both cylinders (cutting out, backfiring). Having fixed the vacuum leak, I'm now back to my original hypothesis: fuel starvation.
Reasons:
- Problem only occurs on the road. Idling, it runs fine. The fuel level while running in neutral is 1-2 mm above the float bowl mating surface.
- Problem occurs with both cylinders.
- There is some fuel flow restriction from the fuel filter.
- The choke provides more fuel, and alleviates the problem. Sometimes, it helps more than others, which I suspect to be because the fuel level gets too low for the choke to help as much
After lunch, I am going to bypass the fuel filter and see if that fixes the problem. To the filter, the flow is reasonable, though the petcock is a little restrictive. I think that may be the problem, since the tank is in pretty bad shape.
Woohoo! Update and progress. I bypassed the fuel filter. It helped, but didn't fix the problem. So I rode back home, got a screwdriver and the clear weed eater fuel line, and rode with my petcock ON.
(unimportant part) I started having severe symptoms of fuel starvation and I ended up on the sidewalk and after checking the fuel level in the left carb and finding it low, I remembered that I was low on gas and it should have been on RES. I then let the float bowls fill up in PRI, turned it to RES, and set off again.
So when I started getting the normal mild symptoms, I rode it for a bit, and when convenient, I cut the ignition, shifted into neutral, and coasted into a "road to nowhere" and checked the fuel level. Left was dead on. Right was about 1/2 cm low.
So it's the right cylinder that's giving me problems. I presume the left cylinder backfiring by itself was due to unburned gas from the right cylinder in the hot exhaust. So much for that diagnostic methodology.
Now, I have a very, very limited set of possible causes. I haven't pulled the carburetors (for the thousandth time) and checked, but it should be a simple case of garbage or dried fuel in the line from the T to the needle valve, or a sticking needle valve.
So now the obvious question: If there's no blockage, how do I prevent the needle valve from sticking? Is there something I can put on it to make it less prone to sticking?
So I hear that this engine is bulletproof. I'm about ready to put that to the test....
Or in other words, cleaning the float valve assembly had no effect. In thinking back, I may have had the bike on the side stand when I checked the fuel level. Anyway, the fuel level is correct for both sides, and I still have the problem.
Maybe a rebalance is called for since I disassembled the carbs, but I need a new top cover for my carburetor first.
Beyond that, I'm stuck.
Hmmmm... doesn't sound like fuel level.... 1/2 cm shouldn't matter much.
Slightly Low float bowl levels will affect the first 1/2 turn of the throttle and not so much w.o.t (wide open throttle) -this is because the main jet is lower down in the float bowl and generally not as fussy.
You balanced the carbs while you had the air leak!! this will need doing again, but to be honest- unbalanced carbs aren't going to cause this fault. during W.O.T the balance doesnt really matter that much. Not enough to give you this problem.
From the video, it looked like you were spraying the EZ start with the carb balancing caps off. I can't tell, but this will really REALLY mess things up if you're riding with them off!
I'm not sure after all these posts, what the symptoms now are??
Running one cyclinder at a time will give you erratic "farting" anyway!
There are numerous causes to what I think your symptoms are..
Bearing in mind I'm not sure what they CURRENTLY are, here's some suggestions:
Slightly blown head gasket, partially duff spark plug, intake manifold leak, main jet missing/fallen out, mid jet and main jet put in the wrong holes, HT leads breaking down, partial fault with electronic ignition, blocked emulsifier jets may have been missed.... er... lots of things!
How about you Drive the bike on PRIME with the float tubing attached (and new plugs), but switch to ON and immediately stop the engine when the fault shows in that order.
Have you re-done the EZ start test, since you fixed the leak?
Also bear in mind that when you have a leak, the engine will quite possibly tick over faster than if you didn't have a leak.
Carburettors are set up for max power and then 'richened' a little to avoid over-heating. More air can speed them up!
This problem sounds like a real Buddha Loves You! you have my sympathies.
When the problem occurs, is one side hotter than the other? I usually spit on the head near the plugs on each side to tell.
If the spits sticks and boils it's ok, if it beads off like mercury -it's too hot!!! are both sides the same?
I'm no expert, but I fault-find things for a living....
If you don't mind, please re-list the most up-to-date symptoms as accurately and in depth as possible, explaining whether it occured after a re-build!
Quote from: johnlaughland on March 12, 2007, 10:04:39 AM
Hmmmm... doesn't sound like fuel level.... 1/2 cm shouldn't matter much.
Slightly Low float bowl levels will affect the first 1/2 turn of the throttle and not so much w.o.t (wide open throttle) -this is because the main jet is lower down in the float bowl and generally not as fussy.
You balanced the carbs while you had the air leak!! this will need doing again, but to be honest- unbalanced carbs aren't going to cause this fault. during W.O.T the balance doesnt really matter that much. Not enough to give you this problem.
From the video, it looked like you were spraying the EZ start with the carb balancing caps off. I can't tell, but this will really REALLY mess things up if you're riding with them off!
I'm not sure after all these posts, what the symptoms now are??
Running one cyclinder at a time will give you erratic "farting" anyway!
There are numerous causes to what I think your symptoms are..
Bearing in mind I'm not sure what they CURRENTLY are, here's some suggestions:
Slightly blown head gasket, partially duff spark plug, intake manifold leak, main jet missing/fallen out, mid jet and main jet put in the wrong holes, HT leads breaking down, partial fault with electronic ignition, blocked emulsifier jets may have been missed.... er... lots of things!
How about you Drive the bike on PRIME with the float tubing attached (and new plugs), but switch to ON and immediately stop the engine when the fault shows in that order.
Have you re-done the EZ start test, since you fixed the leak?
Also bear in mind that when you have a leak, the engine will quite possibly tick over faster than if you didn't have a leak.
Carburettors are set up for max power and then 'richened' a little to avoid over-heating. More air can speed them up!
This problem sounds like a real Buddha Loves You! you have my sympathies.
When the problem occurs, is one side hotter than the other? I usually spit on the head near the plugs on each side to tell.
If the spits sticks and boils it's ok, if it beads off like mercury -it's too hot!!! are both sides the same?
I'm no expert, but I fault-find things for a living....
If you don't mind, please re-list the most up-to-date symptoms as accurately and in depth as possible, explaining whether it occured after a re-build!
Symptoms are:
One cylinder (I believe it's the right) is missing when I try to maintain speed. An example is in 4th gear at 45 mph (~5k rpm). When I maintain this speed, It jerks and bucks. It's a mild form of the jerking and bucking caused when you are, say, running in ON when you should be running in RES. Or, in other words, only one cylinder is cutting out. If I let off the throttle or lay into the throttle, it stops the jerking and bucking. Sometimes, it will backfire out of the exhaust, especially if I have been keeping it constant for a relatively long time. This started sometime in October or November. I don't remember that I did anything to it, but that was 5 months ago.
As far as your post:
I balanced the carbs when I had the air leak, but the air leak was on the top vacuum cap. It would not have been leaking when the carbs were balanced, as the carb balancer would have sealed where the cap was leaking.
The caps were on when I sprayed the starting fluid. Don't worry, I know better than *that* at least. :)
I did retest with starting fluid. The leak was sealed with the RTV silicone.
As far as the suggestions, here are my responses:
Head gasket: no signs of an oil leak. I believe I've heard that it will seep oil if it's leaking.
Spark Plugs: changed with no effect
Carbs: Jets are intact. There is no mid jet on 89-2000 carbs. All holes in the emulsion tubes are clear.
Ignition: I can't say for sure. However, seeing as it seems to be related to the throttle input, I don't think it is. I've checked the spark on both sides, and it's a good spark with the spark tester set at 20kV. The spark looks identical on both sides.
How will running on PRI do any good? It seems that running on ON will be the more appropriate course of action. PRI has no effect on the symptoms. While I didn't run with the tube on and the drain screw out (a good way to lose the drain screw), I did kill the engine when the symptoms were present and coast the rest of the way to my stopping place, so the state of the fuel level at the time of the problem should have preserved.
Edit: changed when it will backfire. It backfires both when I let off the throttle or accelerate. I noticed a backfire when accelerating today on the way home from work.
Okay, another factoid that I didn't bring up earlier because of a mistake I made. Last night, out of desperation, I tested the compression again. I failed to do it correctly and didn't open the throttle. Needless to say, I didn't get a good reading. What I got was 85 psi on the right and 110 on the left. I about had a heart attack until I got out the Clymer manual and realized that I did it wrong.
Today, I did it correctly and got 145 on the right, and 146 on the left.
Now, what would cause the incorrect readings to be so different? My guess is imbalanced carburetors or a vacuum leak (Whee! Circles!). Why? Because obviously the left carb can take in much more air than the right to get such a higher reading. But how can that be? Everyone saw that the carbs were balanced, and that I found one vacuum leak (and it was fixed, though you didn't see that part).
Well, I'm inspecting my homemade differential manometer and I'm noticing that the aquarium line is looking a bit yellow and feeling a bit hard. I'm going to feel really stupid if the second vacuum leak isn't on my bike at all, but rather on my balancer. I'm going to seal it up with RTV silicone and try the balancing again. Before I do that though, I have to get a new top cap, as you can plainly see that the replacement isn't going to yield good results.
Quote from: Egaeus on March 12, 2007, 11:31:54 AM
An example is in 4th gear at 45 mph (~5k rpm). When I maintain this speed, It jerks and bucks. It's a mild form of the jerking and bucking caused when you are, say, running in ON when you should be running in RES. Or, in other words, only one cylinder is cutting out. If I let off the throttle or lay into the throttle, it stops the jerking and bucking.
Just looking at the quoted material my first instinct would be to
check valve clearances. If that's not it, then it's hard not to notice that the problem zone seems to be approximately where the pilot circuit transitions to the main jet. So, when you cleaned the carbs did you check for blockage by squirting carb cleaner through the straw and into the pilot air jet at the carb mouth to see if the fluid squirts out
all of the pinhole jets in the roof of the carb throat aft of the venturi? :dunno_white:
Well, these would be obvious culprits but this thread and its relatives are too much to sort through to know all the troubleshooting that's already been tried. :dunno_white:
Running on primary just overrides any other vacuum problem. It is possible to have TWO faults, which really confuses things.
This is why it's never worth changing more than one thing to find a fault.
-You adjust ONE thing and if it don't cure it, you PUT IT BACK AGAIN!!!
-There's nothing Worse than creating two faults!!!
-Cuz then, you may cure the original problem only to think you haven't!!!
I know this from bitter experience of having to fix electronics that other engineers had their mitts on first!
A partial fuel block will fill up quite quick when there's no demand and only show itself at high demand/ speed.
Switching to ON just before turning the engine off should give you a 'snapshot'of the fuel levels.
Sounds like you have a mid-carb problem, probably lean, since the power comes back in at W.O.T. and backfires a bit on overrun.
Hmmm... could it be the carb diaphragm? That might explain it....
A small hole would not matter at tickover or show at W.O.T, but maybe it wouldn't lift the slide enough at mid throttle??? I'm not sure what the symptoms would be cuz I've never had it.....
Next time you have the carbs out, put them to your mouth like a trumpet, seal the other end with your hand and gently blow. The throttle slides should lift up to the highest point and only drop down when you let the air back out. compare the two. If one behaves differently to the other then have a look at the diaphragms. Don't blow too hard!
I know this isn't very technical but hey, I'm a bodger!
Someone friendly near you should lend you their carbs for a day! I
I don't know what else it could be, but I'm no mechanic, I'm an electronic fault finder...!
PS - you can test the vacuum gauge by connecting Both to the same cyclinder and see if they read the same! (T-link needed)
Valves? Mine ran like crap when the valves were wacked. You can check the slides by taking the tank and the air filter/airbox off and running the motor, you'll be able to watch the slides for a few minutes before you run out of gas...if your vac is incorrect the slides won't lift the same. Dunno? Just tryn to through that out..
For the record, the valves are right on the money. They don't even tick they're so perfect. :icon_mrgreen:
As far as my most recent theory, once I took the carb balancer off of its 2x4, it literally fell apart. There's no way it was sealing. I sealed it up last night and now it will hold a vacuum without any significant leakage except between the two sides (the sensitivity adjustment won't make a perfect seal). However, the total pressure in the device stays constant as far as I can tell.
So I finally balanced my carburetors with the new and improved carb balancer. I took videos of it, so you can critique my method. I did it as a how-to.
Calibration 1 (http://devils.eng.fsu.edu/~rhunter/gs500/CarbBalancerCalibration1.3gp)
Calibration 2 (http://devils.eng.fsu.edu/~rhunter/gs500/CarbBalancerCalibration2.3gp)
Balancing the carburetors (http://devils.eng.fsu.edu/~rhunter/gs500/BalancingTheCarburetors.3gp)
Check for leaks (http://devils.eng.fsu.edu/~rhunter/gs500/CheckForLeaks.3gp)
So after all of that, I went for a long test ride to see if it helped. Well, the symptoms on the road seem a little less severe, but definitely still present. At idle, it seems that is misses worse than before. Since it's doing this at idle more severely, I was able to take a video. I tested the spark on the video as well, so you can see it.
still not working (http://devils.eng.fsu.edu/~rhunter/gs500/WTF.3gp)
One step forward...three or four steps back.
So out of sheer desperation, I rechecked my valve clearance. There are two valves L-In and R-Ex that were ever so slightly out of adjustment (.09 mm and somewhere just under .038). I switched the shims between those two (a 258 and 260...for the third time, long story) and remeasured, and I'm happy that they're correct now. No effect.
You heard how well it was running when I balanced my carbs, right? And you heard how bad it was running in the night video right? Now I can't balance my carburetors. Just ain't happening. It's so off that I can't get it to do anything. I did my best, and gave up on it. I did determine that when the bike starts missing, the right develops more vacuum than the left. I have overthought the significance of that, and I still haven't decided which cylinder that indicates is misfiring.
While I was checking the valve clearance, I did triple check my timing. It's correct.
And while riding yesterday, I put it on PRI at a stoplight and turned it off to see if that helped the idle. It didn't. I left it on PRI, and this morning, I had a puddle of gasoline. Now the needle valve isn't sealing? WTF?!?! When I rebuilt the carb, I didn't replace the needle valves because they looked new. They still do. I don't know what's going on....
I'm really getting sick of this thing.
Hows your carburettor breather hose. Check to ensure it's not blocked.
(http://img141.imageshack.us/img141/3503/carbbreatherdg6.jpg)
If it is you will have an air lock in your float bowls.
Heh, yeah I saw your thread this morning and about jumped up and down because I found something different to check. Believe me, I'm going to check that thing as soon as I get home. I'm going to feel dumb if that's it considering that I've been trying to fix this off and on for over a month. :icon_mrgreen:
Of course, the tube would be perfectly clear of debris. And when I took it out to check it, I discovered that it was messed up. It must have been sitting against the exhaust at some time. Whee! More stuff to replace!
So did this fix your problem? :dunno_white:
No, it was just brittle, not obstructed. I tried running without it just to make sure. Nothing changed. Don't know about the gas leak. I don't really feel like losing more gas...if I have any more to lose. :)
With your float bowls off, have you tried blowing through your breather hose. Does the air flow easily out of the carbs?
I haven't done anything since I checked the line. I won't be looking at it again until probably next week. Just don't have time....
For the still-interested, here's today's progress:
Cliff notes version:
I took the carbs apart and found a little residue on a jet needle and main air jet, but IMO nothing that would be significant. The fuel leak was caused by a pinched seal at the fuel T. I will test ride tomorrow.
The full version:
I haven't touched it for 2 weeks, but I had some free time so today I took apart the carburetors with the appropriate pages of the service manual printed out for reference. Unfortunately, I didn't put them back in and test before it got dark, but here are some observations I made of both carbs:
Diaphragm and piston constant velocity system: Diaphragms are intact. Pistons move freely and equally. I have seen the pistons operate on the bike, and they seem fine. The o-rings that everyone loses are there and in good condition. I replaced all o-rings about a year ago.
Idle fuel system: Pilot jet clear. Pilot air jet clear. 4 pilot bypass ports clear. 1 pilot outlet port clear. Idle mixture screw and o-ring show no visible signs of wear. Screws are set at 3 turns out.
Main fuel system: Needle jets (emulsion tubes) clear and all holes in the tubes are open. Jet needles show no wear. I cleaned some apparent gasoline residue off of one jet needle. Main air jets are clear. One might not have been completely clear, but it definitely is now.
Choke system: starter jets clear, air passages clear, starter pipes clear, plungers move freely.
Float system: Floats have no gas in them (no leaks), needle valve seats are conical (no wear), system moves freely.
Air vent and fuel line T's are all clear. I did find my fuel leak though. The rubber ring that seals the fuel T was pinched the last time I put it back together. It didn't seal correctly. Those rubber pieces are quite poorly made. I replaced them a year or so ago, and they're already cracking....
Mods: 40 pilot jets, 127.5 main jets, K&N in the airbox, and I have raised the jet needles 1.2 mm with #4 washers. This seemed to be working okay for quite a while, but I'd be willing to adjust it if necessary.
Other than the extremely minor issues noted above, I see absolutely nothing wrong inside the carburetors.
Possible adjustments:
- I could adjust the needle, but lowering it would make it run leaner, and raising it more than 2 washers for a nearly-stock setup is (IMO) getting ridiculous.
- Adjust the idle screws out a bit. I don't know why it would all of a sudden be wrong, but it's definitely worth a try.
After seeing nothing wrong, why am I still obsessed with the carb? Because the problems are definitely related to throttle position. Idle and maintaining speed causes the missing and backfiring. Full throttle is great. I wonder what the cops would think if I tell them that I can only ride with the throttle wide open....
I thought I'd start another reply to address some of the suggestions that were mentioned that I didn't respond to earlier, though I did try most of them. I figure it's the least I can do.
Quote from: tussey on February 19, 2007, 10:36:02 PM
try backing the fuel mixture screws out a half turn.
I am going to try this tomorrow if it's still acting up. 3 turns is the recommended amount for my setup and it was working before, but who knows what has changed, and I've exhausted many other possibilities.
Quote from: Wrecent_Wryder on February 20, 2007, 02:10:25 AM
If you (or the PO) have had the tank off, double-check the tank petcock. Make sure the screwdriver slot is exactly parallel to the two feed tubes. It's a bit awkward to turn on and off, so fairly often it ends up not perfectly aligned, which can cause fuel starvation at speed- and setting the frame petcock to "Prime" won't help, because not enough flow is getting that far. You want to check with a good flashlight or somesuch. IMHO, some fair percentage of "phantom" GS "diaphragm" problems are just tank petcock mis-alignment. It doesn't take much.
If that's not it, well, it's a long shot, but try cracking the filler cap open, see if that cures the sputtering (this requires a little forethought and a spare key if you want to wait for it to happen). If for some reason there is NO air vent to the gas tank, the gas will flow fine for a while, until you develop a partial vacuum in the tank, then it will get progressively weaker.
Longer aftermarket fuel lines and/or filter? Make sure they're not contacting the engine head. They're not as far away as you might think, and if they touch, heat can build up in the line and vaporize fuel in it while you're riding.
Just some thoughts.
Definitely not fuel flow. I bypassed the filter that I had added, and it flows great. It will empty the tank in no time.
Definitely not the filler cap. I have an extra key, and I opened it while it was running. No change in the missing.
It starts almost immediately after I get on the road so the engine's still cool and it's been fairly cool on most days I've ridden. It couldn't be vapor lock.
Quote from: Wrecent_Wryder on February 20, 2007, 10:22:51 AM
I took a look at the videos... seems unlikely that our little carbs could suck fuel faster than that, but I've never done anything similar with mine, so I really have no frame of reference to judge what I'm seeing. With some scenarios, though, like the lack of venting to the tank, overheating fuel line, or lots of water sloshing around in the tank under the gasoline, it might flow just fine in a test like that and still be a problem when you're under way... there's just so little pressure with the gravity feed and short drop, it doesn't take much.
Definitely not water sloshing. There's no "blob" on the bottom of the tank, and the tank was filled with ethanol for a bit during the brief ethanol experiment. It would have absorbed most if not all of the water.
Quote from: Susuki_Jah on February 20, 2007, 10:33:51 AM
could it be somthing with valve adjustment. where the engine is bringing in to much air for the amount of fuel? what exhuast are you running? I had a problem with my car one time that was like this. no matter what engine I swapped in it (3 to be exhuast USDM and JDM) it always ran lean ,,, too lean . needless to the say all three engines bit the dust and I couldnt ever figure it out. Untill I figured out what they all had in common. the header on the motor, it wasnt properly designed and I was hard on the car My father can explain it to me again, I'm no engineer but it was causing major problems with the engine.
its just an idea. I could be way off but I thought I would share.
I bragged about the valves not ticking, and they started. I checked the valves again, and two were very slightly off. I switched the shims, and they're all perfect. The measured clearance for all of them is between 0.04 and 0.06 mm. Exhaust system is stock.
You sure its not running rich?
Usually if it requires full throttle to run its because there is too much fuel...
requiring you to have the trottle wide open to let more air in.
Quote from: galahs on April 01, 2007, 06:24:45 AM
You sure its not running rich?
Usually if it requires full throttle to run its because there is too much fuel...
requiring you to have the trottle wide open to let more air in.
Hehe, you threw me for a loop there for a second. No, it's not running rich. The plugs are white.
So, remember a couple of pages back when I took the carbs apart, cleaned the choke, and thought it was fixed. Well, it wasn't my imagination. I finally rode it tonight, and miraculously, doing nearly nothing to the carburetor fixed it again. I rode for about 15 miles, and stopped to get gas, since I didn't know how much I had left after the leak. By the time I got to the station, it was back.
So what is it about the act of taking apart the carburetors and putting them back together temporarily fixes the problem? It's not heat related. The problem shows right back up when it's cold. It's the taking apart of the carburetors that stops the problem. Double-u-tee-eff?
So how's this for a theory. What do you do when you take apart the carbs? Drain the fuel right? But it is never completely drained. Then you take off the top caps, and turn it over and take off the float bowls. I then have been inspecting everything, putting it back together, and it will run okay for a bit.
My theory after my experience last night that I didn't want to share for fear of polluting anyone else's thought process was that there was sediment in the carburetors that was being washed up into the carb body when I turned it over. This sediment was then gradually falling back down into the bowls when the bike was running due to the vibrating and splashing, subsequently causing the bike to run like crap as it made it's way into the jets.
So just now, I take them off, drain the bowls, take them off without turning the carb over, and sure enough, there are significant amounts of tiny rust particles. The particles are small enough that they move freely and are easily suspended in an agitated liquid, but plenty big enough to clog jets (at least temporarily). Here's hoping that I have figured it out. I am going to get a cellulose filter (the current one is just another screen) and see if that helps the rust situation until I get the plastic painted and my new tank on.
I have had similar issues with my bike after taking my carbs apart and putting them back together. I put the blame on the carb boot seal. If it's not perfect, the bike runs horrible/lean. Rust doesn't help either. Mine is rust free.
Just so you know, for the record, the fine rust particles *were* the cause of the problem. I have been moving, so the bike has been sitting forlorn and wanting to be ridden. My test ride consisted of riding it to the new place. It ran great. No missing. I hate rust.
In related news, the tank, the cause of all of my problems, has finally sprung a leak around the JB Weld. It's just enough to keep the epoxy looking wet, but it's a great...opportunity to finally get around to changing the tank. Now that I have a "real job" I can afford to have the replacement plastics painted to match. Woohoo!