Ok, so I still have an annoying dead spot...but after some testing I decided to not only mark the throttle, but make a pretty chart too!
I also adjusted the valves ever so slightly since the intakes were a bit tight. Anyway. The test setup:
1990 - 17K miles
40/150, 1 washer, 3 turns
K&N Lunchbox
883 Sportster Exhaust slip-on
What I notice is between 1/4-1/2 throttle, the bike just bogs down hard. It hesitates and surges a little until I get past that 1/2 way mark. Then it's off like a rocket.
(http://i6.photobucket.com/albums/y217/Soloratov/JettingIssue.jpg)
Can't believe no one has commented on this yet... but then again... there is 'jetting' in the title! :flipoff:
Props on the chart - Diggin' it!
That sounds like a transition issue between the jets. Another washer might help.
Have you done a plug chop at that spot and WOT?
When my carbs in my three jet '04 were stock, I had a surge between 6-8k at half throttle - it pulled harder there than any other spot - so much, it kinda' set me back in the seat (yes, I'm talking about a GS! lol) That surge seemed a little exaggerated on the seat because just before it pulled, it seemed to hesitate for a second. I did a plug chop there and found my plugs were white. But brown at idle and WOT. I added a washer, and then it pulled smooth all the way up - plugs looked pretty darn consistent after that too...
It just sounds very similar, but more prominent in your case - possibly more prominent due to two jets vs three :dunno_black:
:cheers:
- Bboy
The first thing before doing any jetting changes is to make sure the float height is spot on and stable. The clear tube test I'm sure you've heard us mention before.
Your jetting seems reasonable for your set up. Have you replaced your old diaphragms? Old diaphragms can be stiff and cause problems on transition. My bike performed much smoother once I replaced the diaphragms. There may be something you can do to condition the old rubber, but new diaphragms are relatively inexpensive.
I will start with, thanks for the replies....
First, Bombsquad:
I did a float check as one of my first tests and everything is spot on. I also checked the sync and both carbs are nice and in line. The diaphragms were removed when adjusting the current setup, and they are nice and soft. No dry areas or splits.
Bockin:
I figure it has to be either tail end of the pilot jet, or the washer-main jet transition. So I planned on either going up one pilot jet, or adding another washer. I'm guessing as you mentioned it's probably very pronounced due to only 2 jets. I did a plug chop, a good one, and to be honest I wasn't really sure what to think. I have iridium plugs, and the insulator was nice and brown, and the strap was maybe a bit lighter than I would like so I will try a washer and see what happens. I can't imagine an 883 muffler is all that different than say...straight pipes that use the standard 40/150/1 washer setup....I guess I could pick up some 42.5 pilots just to try but that's really just a pain.
Your symptoms get better when you open the throttle slowly ... sorta open only a little and as the motor starts to catch up open more and so on ?
If it does that, then your slides are rising too fast. You may need to close 1 hole in the slide.
Does the bike run fine when you are holding steady throttle @ just under 1/2 lets say ? Then, your problem is definitely the slide rising too fast.
If it acts pops and misfires or surges and what not at steady throttle, then its lean and your float may be low.
Remember problems when opening throttle are rich.
Steady throttle problems are lean. And you can be either, and still have slide rising issues, or be spot on and have slide rising issues.
Cool.
Buddha.
42.5 pilots will give you really really crappy take off, unless you rev it to 3500 everytime at take off, or the motor has had flow work done on the head.
I've read your post again, your jetting is fine. Brown is fine, anywhere brown is OK, the parts that will get the color is where it will get color ...
Cool.
Buddha.
Buddha makes a really good point with carb tuning that makes sense to me in his second paragraph.
Quote from: The Buddha on July 12, 2014, 12:44:32 PM
Remember problems when opening throttle are rich.
Steady throttle problems are lean. And you can be either, and still have slide rising issues, or be spot on and have slide rising issues.
However, in his first paragraph I don't agree with plugging a hold in the slide becuase it's rising too fast. I think that plugging a hold would actually make it rise faster because there would be more vacuum exerted on the top of the diaphragm.
It makes more sense to me that your diaphragms are stiff or leaking (possibly not sealing around the edge due to age?) and not rising when they should. I would think in this case you would see the behavior you are describing, which is basically like taking away the 1/4 to 1/2 throttle.
I completely disassembled the carbs (just in case I missed some cleaning), and did some checking. Everything looks great. Decently clean, nothing weird.
I double checked the diaphragms and they really are very nice. Soft and rubbery, fit nicely and seal well. I'm going to have to go with The Buddha here, only because what he describes is spot on. No matter how fast or slowly I accelerate between 1/4-1/2 she just gives up. I could roll on as slow as grandma and I hit the mark, she's down for the count. I hold steady, and it's like I'm forcing it to run against it's will, but get it past 1/2, and away we go.
I'll stick with the current jet setup, but double check the floats, spray around for some air leaks, and then add a washer at a time to the needle and see if I can get it richer. Testing shall resume tomorrow.
Quote from: Soloratov on July 12, 2014, 09:27:49 PM
I'm going to have to go with The Buddha here, only because what he describes is spot on. No matter how fast or slowly I accelerate between 1/4-1/2 she just gives up. I could roll on as slow as grandma and I hit the mark, she's down for the count. I hold steady, and it's like I'm forcing it to run against it's will, but get it past 1/2, and away we go.
No its not slide coming up too fast ... if you open it like a grandma - it should accelerate pretty much without any symptoms of the issue. Unless you grandma's name is Danica Patrick ...
I'm Stumped.
Cool.
Buddha.
Quote from: bombsquad83 on July 12, 2014, 07:22:48 PM
Buddha makes a really good point with carb tuning that makes sense to me in his second paragraph.
Quote from: The Buddha on July 12, 2014, 12:44:32 PM
Remember problems when opening throttle are rich.
Steady throttle problems are lean. And you can be either, and still have slide rising issues, or be spot on and have slide rising issues.
However, in his first paragraph I don't agree with plugging a hold in the slide becuase it's rising too fast. I think that plugging a hold would actually make it rise faster because there would be more vacuum exerted on the top of the diaphragm.
It makes more sense to me that your diaphragms are stiff or leaking (possibly not sealing around the edge due to age?) and not rising when they should. I would think in this case you would see the behavior you are describing, which is basically like taking away the 1/4 to 1/2 throttle.
We plug a hole. It does slow the slide, the air on top gets out slower and the thing rises slower. Its well known. DJ supplies these plugs and drill and tap ... and I suggest you use a 4-40 tap available @ homedepot and a plastic screw (also HD issue)
A diaphragm with a leak (either @ the edge or the middle) will not come up past a certain point at all. The result will be a bike that refuses to rev past a certain throttle position. Remember - throttle position, not rpm is what carburetion is all about.
Cool.
Buddha.
Solaratov - all I can think of is - well your exhaust can.
Its a weird issue I have never before heard of or experienced, and I've done over 50 bikes personally (OK OK before you think I am some sorta super man mech - 18 of them were mine) ... the 150/40 setup on a 89-00 with pipe and K&N is almost a slam dunk. If people got issues its either a second washer or a air screw or float type issue.
So I'm guessing your pipe is the culprit, cos no one I know has run a sportster can. Either remove it and try it or see if you can persuade a local guy to donate a can to fit and try. I would bet it changes ...
Cool.
Buddha.
Thanks Buddha. I actually found a few things. I had taken the carbs off to do some checking and cleaning, and I found the floats were off after all. I had the covers off and with the carbs upside down I measured and they were sitting way low...sitting at 11.5-12mm. So, I adjusted to the 14.5 in the book. Also, I reset and made sure both sides were synced, and then reset my mix screws at 3 turns...figure it's easier to count off the bike. So...I will get it all put back on, and test with 1 washer, then 2 if needed. If it improves great...if not...I'll be sad because I really like the low slung exhaust, and it sounds great! All part of the experiment I suppose.
He he, OK. Make sure the float level is @ the top of the bowl via U tube method.
Cool.
Buddha.
Quote from: bombsquad83 on July 11, 2014, 03:05:20 PM
The first thing before doing any jetting changes is to make sure the float height is spot on and stable. The clear tube test I'm sure you've heard us mention before.
He he, Bullseye - bombsquad ... Now being bombsquad is that success or failure ? Or both.
Cool.
Buddha.
In all fairness, I did the tube test...but now that I think back it was during a time of frustration, and I only did it when I went to drain the carbs....on the side stand....
Quote from: The Buddha on July 14, 2014, 07:39:23 PM
Quote from: bombsquad83 on July 11, 2014, 03:05:20 PM
The first thing before doing any jetting changes is to make sure the float height is spot on and stable. The clear tube test I'm sure you've heard us mention before.
He he, Bullseye - bombsquad ... Now being bombsquad is that success or failure ? Or both.
Cool.
Buddha.
Just hope that I was able to help. Thanks for the educating on the slides. That has to be one of the most complicated pieces of tuning CV carbs.
Any input is help Bomb. Even if it just got me to double check things...which obviously I needed to do!
Well...I think...THINK i have it fixed. The hesitation is now extremely subtle, and only noticable when I settle into a constant speed. Even then it's very slight. But...LOOK AT THIS RIDICULOUS ADJUSTMENT!
3 Turns
40 Pilot
150 Main
5...yeah. 5 WASHERS
Doth me thinkst I need to go up another main size?
(http://i6.photobucket.com/albums/y217/Soloratov/IMAG0149.jpg)
I still think your diaphragms are causing this. This is only a theory, but I think bikes of our vintage (early 90s) that have likely sat without use for a long time suffer from a stiffening of the diaphragms. They may look soft and not have any pin holes, but it takes more vacuum than it should to get them to lift out of the resting position that they have sat in for so long without use. I know my bike suffered from this and didn't appear to have anything wrong with the diaphragms. Anyway, it's just a theory.
Other thing is, what is the marking on that needle? I believe if it's stock it should read "O-3". Looks a little fatter at the bottom than I remember, but it's probably unlikely it's anything but stock.
EDIT: O-3 is actually the needle jet number for a stock carb. The jet needle you pictured should have "5DH8" on it if it's stock.
Oh, and it's still very possible you should need 2 to 3 washers even with an otherwise perfect carb set up.
By the way, I hope nobody here mistakes me for any type of expert. I'm just sharing my thoughts based on my (limited) experience, which I hope will be helpful.
No worries Bomb. I would completely agree with ya, it could certainly be an issue, but I'm thinking it's just still a weird air filter/exhaust weirdness. Purely because I have it so close now, and because I can roll on slowly, and now, even whack it to any point in the throttle and it's fine. It's purely when I cam sitting at a constant throttle position in that 1/4-1/2 range that I get any hint of a hesitation...which now is WAY better than it was. Now the bike is at least able to be ridden.
If I can get a deal on some diaphragms at some point I will probably grab a pair, but at $23 each from certain places, that's a bit steep.
Quote from: Soloratov on July 20, 2014, 09:00:46 PM
No worries Bomb. I would completely agree with ya, it could certainly be an issue, but I'm thinking it's just still a weird air filter/exhaust weirdness. Purely because I have it so close now, and because I can roll on slowly, and now, even whack it to any point in the throttle and it's fine. It's purely when I cam sitting at a constant throttle position in that 1/4-1/2 range that I get any hint of a hesitation...which now is WAY better than it was. Now the bike is at least able to be ridden.
If I can get a deal on some diaphragms at some point I will probably grab a pair, but at $23 each from certain places, that's a bit steep.
$23 per diaphragm is steep. I got mine on ebay for $35 total for the pair including shipping. The price from the same seller has gone up by a couple bucks, but it's still the best I see out there.
http://www.ebay.com/itm/GS500-GSX600-GSX750-RF900-GSXR1100-CARB-SLIDE-DIAPHRAGM-/201129474510?pt=Motorcycles_Parts_Accessories&hash=item2ed44039ce&vxp=mtr
$17.99x2 + $2 shipping = $38 total
Beautiful. I had found those last night, but I am sometimes wary of buying soft parts like this on ebay. Thanks for the recommendation.
I'm pretty sure its not your diaphragms.
You may have a whistler ... its a leak between the white slide guide and the carb body.
If it gets worse - say you need to go to 6 -7 and 8 washers ... yea guide O ring is gone.
You could otherwise try a 155 main jet ... and a scant 1 washer.
Who knows maybe you have a wee bit of extra wear on the spacer and the slide. It has sunk the needle 1-2mm ...
I've seen people wear the white guide to the point the slides will rattle, and the needle out of that carb was so machined looking ... maybe you have a needle that has worn the part where it sits in the slide.
I dunno ... diaphragms with leaks wont let the thing get over a certain rpm and that rpm will vary depending on the load. 8k in 1st, 7k in 2nd, 6k in 3 rd, 5k in 4th, 4k in 5th etc etc ...
Rattly slides ... see if you can feel too much play when the slides are installed in the carb.
Cool.
Buddha.
Hmmm. I know the white inserts were used replacements for cracked ones. Not sure how old they are. Am I looking for play in the slide itself or just the needle?
I have some 152 and 155 jets here, so i will try the 155's and see where it put me. Otherwise, I might just go online and grab one of those cheapy Emgo mufflers since I know people run those with standard open pipe jetting, or on the bay I can get a replacement stock for cheap too. Just don't want to dump a lot of money on it before I know whats wrong, but I know lunchbox+stock pipe is pretty iffy too.
You'd have to look for play in the slide. Not needle. That has some play and its OK.
Cool.
Buddha.
I'm glad you guys are hashing this out. I've been dealing with the exact same thing and between me(little knowledge) my mechanic bud (cars more than bikes), my bike guru friend (scattered knowledge), we've gone the other direction. I'm running k&n lunch, Vance and Hines full, 40/150, no washer or clip 3 @ 1 turn Same symptoms. I went to clip pos. 1(lowered the needle) out to 2.5 and it limited the symptoms. Now I'm screwing with going smaller on the mains, clip 3, 2 turn base point. I'm at 140s right now, but I think I'm going to try the 155s as well, and see if I can mix it out.
Side note, until about a week ago I had another set of slides in that were drilled. Symptoms were consistent. And few other theories have surfaced, poor compression, valves and spark. No tests have been done yet
92 20k miles
Quote from: Nakedguy on July 28, 2014, 07:40:30 AM
I'm glad you guys are hashing this out. I've been dealing with the exact same thing and between me(little knowledge) my mechanic bud (cars more than bikes), my bike guru friend (scattered knowledge), we've gone the other direction. I'm running k&n lunch, Vance and Hines full, 40/150, no washer or clip 3 @ 1 turn Same symptoms. I went to clip pos. 1(lowered the needle) out to 2.5 and it limited the symptoms. Now I'm screwing with going smaller on the mains, clip 3, 2 turn base point. I'm at 140s right now, but I think I'm going to try the 155s as well, and see if I can mix it out.
Side note, until about a week ago I had another set of slides in that were drilled. Symptoms were consistent. And few other theories have surfaced, poor compression, valves and spark. No tests have been done yet
92 20k miles
Needle clip positions ??? you've got a dj needle in there ? If so your right main is somehwre around 136-134.
If its the stock needle - AKA some euro country - then its like 150 or thereabouts.
Cool.
Srinath.
Nope factory pro kit needles and mikuni jets...
I gave the dj needles to a friend who thought the crazy taper would help on his 78 cb
I'm going to replace the orings in the floats, they seemed a little rough. Popped in the 155s, mid clip or stock on the needle at 1 turn, still boggin but fun. I'm thinking go leaner on the needle and fix the orings, see what happens.
155 ? or you meant to say 145 ?
I am confused 100% with problems with 4-5 GS'es ....
Cool.
Buddha.
Tried the 145s 140s 150s and now 155s. With the 155, There was puff of dark smoke from the exhaust when blipping the throttle and over rich stall out at idle. Going back to 150 and testing the spark. Buddha, I know very little about bikes and even less about carbs, all I do know is what I've read here and have been told by people with a stronger grasp of the subject at hand. The only consistent variable to this equation is the 1/4 -1/2 bog. It's driving me nuts really, but it's about the journey, right? :dunno_black:
Floats have been checked and rechecked. Everything has been cleaned thoroughly. Orings have either been replaced or checked, carbs have been synced, plugs have been swapped twice. Slides have been swapped, diaphragms have been swapped, I've tried multiple mix screw,needle, main jet, combos with little success.
I'm willing to do the work, but this is getting ridiculous. Any ideas are welcome
Sounds to me like you and I are in this little journey together my friend! I did a few other things, including completely removing the restrictor plate that is inside the sportster mufflers. Basically it makes it a straight through pipe. Same deal as any other slip-on without baffles. That leaves me with a simple option. I will set it to the usual accepted setup of 40/150 3 turns and 1 washer. At that point, if it still does not run properly, or at least, REALLY close, then I am left to only assume something is wrong with the engine itself. I will add that I have tried all kinds of combos as well, and while they did provide differences each time, it was never consistent richer or leaner.
As a test, here is a plug chop I did right after removing the plate...still having the same exact symptoms, in the same 1/4-1/2 throttle spot. The setup was this:
Flow through pipe
Lunchbox
40/155 jets
1 washer
2.5 turns
Riding results were unchanged. 0-1/4 throttle awesome. 1/4-1/2 it just chugged, coughs, and sounded like it was stalling out. After 1/2, (with this setup) it acted a bit rich, but still accelerated ok.
(http://i6.photobucket.com/albums/y217/Soloratov/IMAG0152.jpg)
(http://i6.photobucket.com/albums/y217/Soloratov/IMAG0153.jpg)
Oh, and to clarify, the body of the plugs are not burnt or anything...thats engine paint. I had taped the caps of the plugs but left them in to touch up the top of the motor. The plugs themselves are only 1 season old and have a nice bright spark.
I'm testing my electronics today and if that doesn't help, I'm going to throw the old exhaust back on (some cobbled together d&d mess). And if that doesn't help, I'm probably going to rebuild the engine. Will report back
I swapped the coils tonight based on my friends theory. Went back to 150/40, raised the needle to what would be 1 washer and 2.5 turns on the carbs. Will reinstall the carbs tomorrow for some testing
I'd put money on that not doing anything. If there were a problem with the coils, it should affect the whole throttle range, not just one single section. If anything I would think idle would be where you would see a coil problem the most...at leas thats how it was with my friends bike. Weak coils get the least amount of power through them at idle, and his would just start horribly hard, and then idle really bad before dying, rev it up, and it seemed fine.
I'm trying anything at this point
No change on the coil, jet, needle screw changes.
Pull you lunchbox and tell me if you get some blow back as well, while blipping your throttle.
Gs gurus, what causes blowback thru the carbs?
Quote from: Nakedguy on July 30, 2014, 01:50:06 PM
No change on the coil, jet, needle screw changes.
Pull you lunchbox and tell me if you get some blow back as well, while blipping your throttle.
Gs gurus, what causes blowback thru the carbs?
Tight intake valves?
Not beyond the realm of possibilities.... Could anything else cause blowback? Timing? Low compression? I want all possibilities so I can take care of it and use up some treadlife
This hit and miss nonsense has to end
Quote from: Nakedguy on July 30, 2014, 03:06:02 PM
Not beyond the realm of possibilities.... Could anything else cause blowback? Timing? Low compression? I want all possibilities so I can take care of it and use up some treadlife
This hit and miss nonsense has to end
Timing is another possibilty that I thought about later after posting the first time. No harm in testing compression and checking the valve clearances and timing.
Doing all of this with a little help on Saturday
Here's what I've got so far. Timing is good, spark is good, compression is good, valves are good and plugs are good.
Carb boots had a leak, not on the engine side but on the carb side.(biggest issue and not that big of a leak.)
After fixing the leak
Started with the mains, 150, middle clip or stock needle, 2.5 turns. Way too rich.
Went to the 145s at 1 washer or clip 4, 2.5 turns, still rich.
Went to clip 1, or the same distance as 2 washers above stock on the needle, 3 turns.
Bog is gone! feels flat-ish but decent
I won't have any more time to mess with her until Friday, but really getting close. Having the factory pro kit adjustable needles is really making the difference in tuning.
I'm with you. Here is what I have now. It just seems so wrong....
I went and sealed up the joint between the muffler and pipe. Then removed the restricting plate from the Sportster muffler. I basically have a 1 1/4" straight muffler. It's an open pipe with SOME baffling. So I work under the assumption is would be the 40/150/1 washer setup. Assumption wrong.
Currently:
40/147.5/no washer. Seems FAR better than any other test so far.
Could this possibly go to a 145 main!? I'm going to run out to the bike shop and pick some up to try...just seems so off...
What is the diameter of the sportster pipe vs some of the other aftermarket open exhausts? A smaller diameter can actually provide more speed to the exhaust that does a better job of scavenging air from the cylinders for better flow. If the sportster exhaust has a bigger diameter, it could be slowing things down and not performing as well as a smaller diameter pipe might. There is obviously an ideal exhaust diameter that is not too small and not too big.
The inner diameter of the muffler is 1 1/4 inches. There is technically some baffling going on since I did not remove them, I just gave it a straight shot out.
After some more tests....
40/147.5/NO washer and 4 turns on the air screw! Even better performance now. So, I will stop out and pick up some 145's and then reset the mix screws to about 2 turns and start there.
:thumb: