So Before the girlfriend left for her Italy trip her '02 GS500 had an issue where when she came to a stop the rpms would stay high and not come down.  So I take the carbs apart and clean the ever living bageebus out of them.  I replaced worn o-rings and a broken jet (stupid screwdriver) and gaskets. 

Remove the caps on the Idle screws and screw them all the way in and go one turn out.

Put everything together and start the bike up, gets to operating temperature and I adjust the idle screws to 3.5 turns and everything is peachy.  Idling smooth as silk.  Choke does what it is supposed to.  I go to give it gas and at lets say a 1" rotation of the throttle bike dies.

• removed air filter and watch the accelerator pump bounce up and down.
• Replace vacuum hose on the petcock vent
• Put everything back together and sprayed starter fluid all around the gaskets, intake manifold, and carbs waiting for idle to speed up (nothing)

Any ideas on anything else I should check.

Thanks in advance.

When you say "accelerator pumps", you mean the slides, correct? If so, they should only move depending on the butterfly valves (controlled by the throttle cable). Did you check the condition of the rubber diaphragms? Sounds like maybe a pinhole or some other vacuum leak around them.

Forgot to add - your hanging idle wouldn't be caused by that though. High idle is usually caused by an air leak between the carbs and motor (I know, you've checked that already........)

Yeah by accelerator pumps I mean the slide.  The move freely and bonce up and down when I give it gas.  I check for leaks using starter fluid and there were none to be found.  I also checked the diaphragms with a light behind them and didn't see any holes.  Thanks for the ideas though doesn't seem like the cause of my issue.  Idle is fine.  It's only when I give it gas it dies.

That "bouncing up and down" part is what concerns me. Does it look like they are shaking up and down, or are they moving a considerable amount? And have you tried putting the airbox back on?

uploaded video here.  They are bouncing significantly but I'm guessing it's because of the lack of fuel.  idk.     It's been in the garage for 2 weeks while I've been troubleshooting it and browsing forums.  I'd really like to get this running before she gets back from Italy.   
Appreciate the help.  Typically if the diaphram has holes in it you can manually hold the sliders with your fingers and give the trottle a twist and the engine will go.  This is not the case.  It's seriously acting like it isn't getting enough fuel.  In the morning I'm going to check the fuel float height again.  Honostly I'm not sure if I checked that on this latest rebuild or not.  This is the 3rd rebuild mainly because of the dealership giving me the wrong parts and doublechecking after the fact.

http://www.youtube.com/watch?v=xUX8diAV_ME&feature=youtu.be


Edit-probably helps to explain the video.  So bike is idling,  I give it gas you'll see the sliders pump.

Yeah, that doesn't look right to me......

I'm trying to think what would make them jump at all.......maybe if the butterfly valves were somehow flopping around. In all honesty though, I would say it's a problem around the rubber diaphragm. Like a leak around the edge, or maybe a leak in your choke plungers (if they share any passage ways above the slides).

I think you're carbs would have to be really dry to cause a problem like that just coming off idle. Not just a mm or two on a float adjustment.

Check the exhaust valve clearance. I just spent a month (well, working on it a few hours per weekend) chasing a similar problem. I checked and triple-checked everything on the carbs and could not get the bike running properly:
- cold, it idled fine, but tended to die when opening the throttle
- warm, the idle would hang high, and the bike would stumble/die when giving it part throttle - to take off, you have to peg the throttle wide open.

In the end both of my exhaust valves had 0 clearance.

Either way, it only takes a few minutes to check the clearance. Remember to buy a new valve cover gasket ahead of time though.

Most of the time you should be able to reuse your valve cover gasket.  You will need some high temp gasket sealer adhesive though to put a dab on each side of those half-circle sections of the head when you put it back together.

There are several valve adjustment instructional videos around.  Just search.

I did a complete overhaul on the bike a couple of months before the initial problem started occurring, new plugs, tighten head bolts, new chain, changed oil, checked clearances, so everything was within specs then.  Two months later the rpm issue came about after the bike sat unused for a couple weeks.  She would come to a stop and the rpms would stay high.
No worries I thought, running lean, carbs probably need cleaned/rebuilt so I did that and the result is this new problem.  didn't get to check float levels this morning, will do that tonight when I get home and if that doesn't net anything I'll take the carbs apart a third time and go by the numbers again.

So talking to a car buddy "accelerator pumps" are the diaphragm which Big Rich mentioned earlier. 

When the carb goes from Idle to open throttle it needs a quick shot of gas before the carbs can send the proper fuel mixture through to keep the bike running.  (Air flows faster until it has enough velocity to start pulling the atomized gas through).  The symptoms I described to him is a common problem on cars with bad "accelerator pumps"  So I'll go home and concentrate on that.  Does anyone know of a good way to test the diaphragm other than visual inspection?  Maybe I have a vacuum port clogged up or something.

Again thanks for taking the time out to help. 

Have you placed the caps in the vaccum plugs?

Did you checke the float heigh? The only way that worked for me was the transparent tube at the bowl drain method. Thats the only way you can check the there is enough fuel in the bowls.

Can you run the bike of a temporary tank, without the petcock? The petcock may be busted!

Pretty sure I just figured it out.  My advice to people taking apart the carbs.  I had to use an Impact driver the first time taking my carbs apart because the screws were in there too good.  Even though I put a piece of wood under the carbs and gently tapped the impact driver progressively hitting harder and harder.  This is what happened.  On both carbs.  Yeah super ecstatic about this one /sarcasm.

Wait........so those little gaps were there the entire time? Or did you just recently do that since starting this thread?

that is why the more modem carburetors have alloy caps   No more gaps from heat warped plastic or bent flanges from using impact driver on soft alloy

Big rich, the whole time.  Since I initially took the Carbs apart with the impact driver.  Next thing is how to fix it.  Wonder if a machine shop could do something about it out, or if I need to just put a crap ton  of gasket maker in there.

This might sound stupid but I think I would try straightening them flanges out.  I'd take a brass drift and shape it on the end so it semi fit that flange.  Then I'd place the carb upside down on a flat block of wood and tap on the back side of that flange with a medium ball peen hammer and drift, and see if I could move it back a little at a time.  You got nothing to lose at this point.  I know it's expensive, but your real fix is to buy her another set of carbs.  I think you know that, but the wallet is resisting.  Good Luck!

Instead of gasket maker in a tube, I would try the cut-to-fit stuff from an auto parts store. In the long run though, you might be better off saving up for some new carbs........

+1 to cheetahman

Take the carbs all the way apart, lay them bent side down on a hard flat preferably wood surface and very carefully tap it back to flat. You can bend aluminum all day if you work SLOWLY.
(don't use goop on the diaphragms, you'll hate yourself later.)

Then try it all again.

And dont use a hammer on any carbs ever again! You are a crazy person. < this obviously something you've learned.

I would replace all the screws for caps and bowls with allen key screws. your life will get easier.

oh and go out and buy yourself a quality #2 phillips head bit set. Bits wear out, and when they do, every screw you try to remove gets destroyed. thats life.

Good luck, dude!

Appreciate the feedback,

Took the carbs to a shop to get straightened out, Same issue got the flat gasket maker and cut out to fit carb, still same issue.  Problem is these carbs are not the carbs any diagram shows on this bike.  The girlfriend is the first and only owner of this bike so Suzuki must have ran out of parts during production and replaced it with another model of carb.  All of the screws were replaced with allen bolts.  It wasn't an issue of the screw driver bit, it was an issue on how those bad boys were torqued in there.

I took it to the dealer for them to take care of I'm tired of going to the dealer, ordering parts based off the diagram they are supposed to have for my bike, wait a week, get the part to find out it isn't correct then they have to go through the trouble of locating the part.  Same thing when I order the parts online.  We are just trying to get this thing running again so we can sell it.  We've purchased another bike for her at the beginning of the season and it's been sitting in my garage waiting for me to have time to work on it.

I had a very similar problem.  What I found was this:

You want to minimize the use of the idle screw (the one
that hangs down between the carbs).

It has a major impact on the way the GS runs.  If that thing
is even 1/2 a turn too high (at least on mine) I get tremendous
hanging idle problems.

The way I solved it was to let the bike get completely warmed,
then back out the idle screw and bump up the pilot screws
1/4 turn on each carb until the idle was stable and the bike
didn't hang while returning to idle from higher revs.

These carb are stranger than any others I've worked on.  The
pilot screws should be adjusted to be as lean as possible while
maintaining the idle at 1200-1500.

If not, the idle screw (between the carbs) tends to act like a
secondary choke.  You can get the same effect on my GS by
also running with the choke slightly on with all other aspects
of the carbs tuned perfectly.  When you roll up to a stop, the
idle hangs at 3000.

(rich idle circuit)

The problem was even more pronouned when inserting shim
washers under the needles with the stock needles.  I've
found it's much better to change jets than it is to insert
washers if you're using the stock suzuki needle.  If not, 3000
rpm is WAY too rich.  Guess it's just the profile on the
stock needles.

After a week's worth of playing with jetting, I now have my
GS purring like a kitten with no flat spots and no hanging
idles.  Takes a few minutes to warm up, but runs great after
that.

TJ