ok  i let my project sit for a while.. went to start it it wouldn't start so i puled carbs. cleaned with carb cleaner and flushed everything with fresh  fuel. readjusted mixture screws to 2 1/4 turns out....went for a ride and the bike jerks  alot under load in mid rpms  also revs odd at same rpms in neutral but not as bad...i adjusted the mix again to 2 3/4 turns out stil there. and bogs some after the rough rpm area of 3-5krpms.... so i have a few questions whats going on? are the carbs supposed to have spacers on the needles stock? as mine have plastic spacers on each needle measuring around 1-2 mm.  what jets are supposed to be in bike stock? the carbs currently have 122.5 jets 

I don't know what year your GS is, but this link will show you an exploded diagram for the original '89 - '00 GS500 carbs (all images apply to US market carbs ONLY):

http://images.powersportsnetwork.com/fiche/images/Suzuki/1989/Motorcycles/2103_12.gif

This is the diagram for the 2001 / 2002 carbs:

http://images.powersportsnetwork.com/fiche/images/Suzuki/2001/Motorcycles/2102_13.gif

And this is the diagram for the 2004+ carbs:

http://images.powersportsnetwork.com/fiche/images/Suzuki/2004/Motorcycles/7247_13A.gif

NOTE: The information I am providing here applies ONLY to the original ('89 - '00) GS500 carbs, so if you have a different model, this information probably won't help you too much... but you can still learn from it, so I hope you'll take the time to read it anyway...

Look closely at numbers 5, 6, 11, and 32 in the '889 - '00 diagram; make SURE that those parts are assembled in the correct order. Next, look for part number 26, which is a SMALL O-ring that fits into the top of the carb body, close to the top of the diaphram (it is normally covered by the carb top). If it is missing, pinched, cut, or in any way damaged, you'll have problems similar to what you've described. Those O-rings are easy to lose / overlook when you disassemble a carb, so make sure they're seated properly when you put the top back on each carb. If they're missing, they're listed as part number 13509-17C00. You need one for each carb (might as well buy two and replace them at the same time), and mrcycles.com lists them for $2.94 each; of course, you can probably expect to pay a bit more at the dealership, but the dealer needs to make a profit to keep the doors open, so if you've got a good dealer, be sure to support him. These o-rings aren't  high-ticket items, so the dealer isn't going to buy a house with the profits from the sale...

The stock pilot jets (number 19 in the diagram) are size 37.5; for good basic carburetion, you'll need to install at least #40 pilots. The main jets you mentioned (size 122.5, number 31 in the diagram) are in fact the stock main jets, and you might as well order new (larger) pilots (at least size #40) and mains (at least size #125) NOW, or ASAP, because the stock jetting is TOO LEAN. If you're using an aftermarket airfilter or exhaust system, you'll need to install even larger jets... so follow the advice in the wiki:

http://cgi.stanford.edu/~sanjayd/gs500/Main

http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Rejetting

http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Rejetting-LeanOrRich?

If you've checked those links, you've probably noticed the jetting matrix (in purple), shown here:

http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Rejetting

and the same information displayed in basic tables just below the two matrices (one matrix is for the 1989 - 2000 model carbs, and the other is for the 2001+ carbs). Get familiar with the jetting matrix for your year model of the GS; it can help get you in the ballpark with jet sizes, as long as you aren't running open pipes with no air filter...

OK, that should be enough information to get you pointed in the right direction on understanding what you're dealing with, and you should be on your way to correcting these problems. If you're not familiar with carb work, now's as good a time as any to start learning more than you already know. Judging from what you've already written, you're not afraid to dig into the carbs, and that's a good thing.

Whatever else you do, do NOT make changes to your carbs (don't try to modify the needles, don't throw away ANY parts, even if you're convinced they're not the right ones, etc.), or you might regret it. DO ask for advice here before making any major changes, and the carb gurus will help get you to the promised land.

Take your time, read through the collected wisdom provided in the wiki, and ask for clarification of anything you don't understand. Since you're an experienced dirt rider, you're probably a LOT more familiar with carburetion than most of the people who post here, and that is to your advantage. With a little time and patience, you'll install the new jets and be back on the road before the snow melts.

I'd wish you luck, but I really don't think you need it. With your background, you can probably field-strip a carb faster than most of us can check tire pressures... but good luck anyway.

when you cleaned carbs with carb cleaner, did you soak em for a solid day?

Now that I think about it, I hope you didn't let the carb cleaner come into contact with any rubber parts, because the carb cleaner can do a LOT of damage to the o-rings and carb diaphragms, among other items.

While you're checking for the little o-rings I mentioned in my first reply (part number 26), check the carb diaphragms to make sure you can't see any daylight through them. A tiny pinhole in either one means you'll need to buy a replacement, NOT a cheap item.

Why do we have topics about Jerking and Head Shaking atm? 


Warning to all GS members... keep it up and you'll go blind!!!







(back on topic please)

sorry i have a 1990 gs500e  while the bike sat i installed k&n pod filters and a v&h exhaust  so i def need larger jets and pilots now?

as far as part 26 goes.....mine didnt have em when i took it apart.. i was wondering if there was supposed to be something there....but why the rough motor all of a sudden?  i actually have a rubbr o ring kit i prob have something that small in it as i do carb work to my own bikes alot but i havent messed with anything this new in a while hence my questioning the o ring when i had it apart

Typical Lean Conditions:
- Poor acceleration; the engine feels flat.  CHECK
- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.) CHECK
- The engine runs hot, knocks, pings and overheats. CHECK
- The engine surges or hunts when cruising at part-throttle. CHECK
- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle. CHECK AND  CHECK
- The engine runs better in warm weather, worse in cool. CHECK
- Performance gets worse when the air filter is removed. UNKNOWN ive ben runing with no filters k&ns are stil in package unopened

so would like 125-130 jets be fine for now? i can go to my neighbor an he will give me a set for free i think he has pilots too as he has a 1990 suzuki gsxr  and has tons of jets.... he is also the one who gave me my v&h free nothing wrong w it either lol he jus wanted a chrome exhaust instead of aluminum

Quote from: GSnoober on March 25, 2008, 03:17:54 AM
Now that I think about it, I hope you didn't let the carb cleaner come into contact with any rubber parts, because the carb cleaner can do a LOT of damage to the o-rings and carb diaphragms, among other items.

While you're checking for the little o-rings I mentioned in my first reply (part number 26), check the carb diaphragms to make sure you can't see any daylight through them. A tiny pinhole in either one means you'll need to buy a replacement, NOT a cheap item.

no i didnt i took everthing apart and separated all rubber parts before i even thought of using carb cleaner  i know first hand what damage it can do

as for the rubber diaphrams they are good but i can repair small holes in them i kave this cool ruber stuff for rubber coating toosla that works wonders on diaphrams and lots of other rubber seals and parts
its also an excelent fix for small seat tears or holes as youcan apply it and let it cure a little then texture it by applying a piece of leather to it to give the leater look to it.. the stuff is around $5-$10 for a pint and that lasts a very long time..... im on my same can now for 3 years

how far out can i turn my mixture screws? im at 4 1/4 turns and the jerking is almost gone....would it be ok to just adjust the mixture screw untill it runs good and leave it untill i can get the right jets an pilots?

A friend warned me not to turn the mixture screws out more than 3 to 3.5 turns on the GS carbs, because (according to him) the mixture screws will vibrate out if you turn them out any further. He had both mixture screws set for ~ 3.5 to 3.75 turns out from fully seated, and one of them fell out while he was doing ~ 70 MPH (indicated) on the highway. He didn't know what the problem was until he stopped on the shoulder. He shut off the engine, then dismounted to see if there was an obvious problem. For some reason, he noticed that the mixture screw for the left side carb was missing. The other mixture screw had backed out quite a bit, but hadn't fallen out, though it probably would have happened within a short time.

This is a decision I can't advise you on; if you lose one (or both) mixture screws, you won't be going anywhere until you can track down replacements. If this was MY motorcycle, I'd bite the bullet and do the carb work ASAP. Some people don't mind playing the odds, thinking nothing bad can really happen, but when I do that with my motorcycle, the whole world goes to hell every time, and I always regret pushing my luck afterwards, so I've learned not to tempt fate too often these days.

oh....well ill squeeze some rubber o ring s in front of the mix screws so they wont move