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?

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.





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