Okay, so I just took everything apart, and here's what I have found so far:

* The carbs seem fairly clean.  I realized that I don't have any carb cleaner, so I need to go to Kragen and get some.
* The diaphrams don't seem right.  On my old ZX6E, they seemed a lot more "springy", meaning that they snapped back into their original shape.  The GS ones look all crinkley, and seem worn out to me.  They don't spring back real well.  Should I replace them?
* I found a mysterious tiny black rubber gasket stuck to my hand when I took the carbs apart.  I have no idea where it goes...  :dunno:
* The spark plugs are in pretty good shape.  The left side shows good mixture, but the right side shows a little lean.  How do I fix that?  (The right plug was also not very tight when I pulled it)
* The header bolts needed tightening, but weren't horribly loose.
* I checked the inside of the gas tank again, and it still looks clean.  No floaties or clogged screen.
* The rubber gaskets for the carbs and air box appear to be in good shape.

I mostly wanna get you guys's opinion on the diaphrams before I put everything back together.

Thanks!
Jason

Original Post:  

So, I've had my 89 GS for about 3 years or so.  It has always run flawlessly (I take good care of my baby).  Just recently, it started idling really low (almost dying) when I turn the choke all the way off (yes, it's warmed up).  I tried the idle adjustment screw, but that doesn't work so well.  I have to turn the crap out of the screw to get it to a good idle speed (1200-1500).  When I do that and give it some gas, the RPMs stay way up for a couple seconds, and slowly come down (scary around turns).  If I ride it with the choke ON a little (idle screw set back to "normal"), it seems to idle ok.  Riding with the choke OFF seems fine - no flat spots from what I can tell, so it might only be an idle issue, and not a mixture issue.  I have not been messing with the carbs or anything...  Any ideas?

Thanks,
Jason

I'm mentally preparing for tearing the bike apart this weekend.  Gimmie some ideas, people!  It MAY have started when I changed the oil, but I didn't do anything different.  Used Suzuki 10-40 oil this time, cause the dealer stopped carrying spectro for some reason.  The plugs shouldn't be toast yet, but I can check em.  My K&N could probably use a good cleaning, but shouldn't have screwed up the idle all of a sudden.  I'm not sure how old the fuel is, but the tank's almost empty now.  The fuel shouldn't be more than a month old.  The tank doesn't have any crap in it (it's off a 97, and totally clean inside).  

So what's left??  Dirty carbs?  Clogged fuel filter? (Does the GS even HAVE a fuel filter?)

How many miles since your last carb cleaning or valve adjustment?

I've been having similar issues, bike will stall when choking down after warming up as well as when letting the throttle go from 5000 rpms to the bottom. My bike's at the dealer getting serviced... once I get some answers from them I'll repost...

That would be cool if you could let me know the outcome.  Haven't cleaned the carbs since the rejet (3 years?), and never adjusted the valves...  I didn't wanna break it if it was running so nicely!  I have put about 10,000 miles on the bike since I've had it.  It has around 23,000 miles?

Quote from: mrblinkThat would be cool if you could let me know the outcome.  Haven't cleaned the carbs since the rejet (3 years?), and never adjusted the valves...  I didn't wanna break it if it was running so nicely!  I have put about 10,000 miles on the bike since I've had it.  It has around 23,000 miles?

Valve problems should come on slowly - but the valve check interval for valves is well below 10,000 miles - you need to adjust them (at least check them) regardless of other problems.

Carb having a bit of dirt can come on very suddenly - could be that.

About a thousand other possibilities - small vacum leak from the hose to the petcock, crack in one carb boot, loose carb clamp, missing vacum spigot cap.

I would start with the valves since that needs to be done anyway.  Since you need to remove the tank to do that, it is a perfect opportunity to inspect & replace the fuel and vacum hoses, caps etc and even to run some carb cleaner through the carbs.  Change the plugs while you are at it - if this does not fix it then remove the carbs and do an internal cleaning.

I have the exact same problem.  I'm taking it in to be serviced this weekend, will post up when I hear whats what

I'm picking up the bike tomorrow from Berts in Covina. Service was a hassle (took forever) but they said that my issue was dirty carbs. They also suggested the bike really needs a valve adjustment, so maybe I'll be ordering one of Kerry's dvd's...  At least it isn't stalling anymore!!!!!

Thanks for the update!  I'll definetely keep an eye out on the carbs and let them know to give it a good look.


Kerry's DVD is A+++,  DVD plus a trip to get some tools and you'll be set to go.

Thanks for the info.  I'll clean the carbs and change the plugs this weekend.  I think a valve adjustment is a little outa my league.  What is this DVD you speak of??

The video thread is here.... but I don't know if its generally available yet.  http://gstwins.com/forum/viewtopic.php?t=13483

Trust me, I've never wrenched anything on my bike and after watching this (I was a guinea pig) I have no doubts that I could do it myself

Man, that Kerry guy is pretty damn cool.  I always thought that the people on this forum were mighty helpful, but holy crap!  I hope he finishes the final cut so I can order one.  I'll even give him extra $$!

Quote from: mrblinkI hope he finishes the final cut so I can order one.

Patience is a virtue....  

It wasn't one of my better ideas to start this whole video thing just before going on a 1-week vacation on the other side of the country, with only dial-up access.  I have felt obliged to spend a good bit of my time looking around southern Florida because I may never be back, so the video editing hasn't begun yet.  (So much for bringing a couple dozen CDs and jewel cases with me.  :x )

I plan to hole up in my hotel room tomorrow, but even so I have some additional footage to take when I get back home.  Hang in there!

Hey man, don't rush TOO much.  It's something I want to learn, but I'm still a little scared.  This way I can just blame it on you when people give me a hard time for my overdue valve adjustment.  

Quote from: mrblinkHey man, don't rush TOO much.  It's something I want to learn, but I'm still a little scared.  This way I can just blame it on you when people give me a hard time for my overdue valve adjustment.  

I got a hard time from the service dept when I went to pick up my bike, they were VERY serious about the valve adjustment (since I hadn't had it done since 600 miles and i'm pushing 10500 miles). I'm going to be attempting the valve adjust. next weekend since its a long weekend and i'll have more time to mess around with it.

Just to update, my idle/stall problem is fixed. All they did was drain the "float bowls" and I guess some dirt came out. Amazing that a little dirt can cause so many problems!! I'm going to attempt a full carb clean soon too...

I'm waiting on a video for that   :mrgreen:    Yeah, I'm that bad. lol

I edited the original post.  I thought it would pop back up at the top of the list, but I was wrong.

Just got back from the shop myself to get new tires put on.   I had him look it over and i went for lunch. He originally thought it would be a carb rebuild. When I got back he told me that he had taken the bike out for a spin, and adjusted the idle speed,  (Cold it idles at 1000, after riding about an hour in city conditions it was up to 3500)    

He said that he couldn't understand for the life of him why the previous guy had put on the K&N airbox, and that it actually is hurting my low end HP. He also informed me that the rejets were way too big, that they should only be 1 size bigger than stock, not what I have going on right now.   He suggested I put the stock airbox back on, and rejet the carbs to a smaller mains, pilot.

This is what the bike has now.   40 pilots, 147.5 mains, K&N Pod filter.
This may help someone, I don't know.  If anyone else can second this opinion, let me know

Quote from: mrblinkOkay, so I just took everything apart, and here's what I have found so far:

* I found a mysterious tiny black rubber gasket stuck to my hand when I took the carbs apart.  I have no idea where it goes...  :dunno:

If that is the tiniest o-ring you have ever seen, then it is for the vaccuum spigot.  It goes on the top of the carb just below the vaccuum spigot, next to the groove where you seat the diaphragm.  There should be a small depression for the o-ring.

You want that o-ring there, and make sure that it is in good shape (not torn or anything), otherwise your bike will mysteriously run like cr@p. :guns:

Cheers,
e.

Found the o-ring depression.  Thanks Ed89!  Also, about the diaphragms...  I didn't realize that they folded over (realized it when I saw the parts diagram on bike bandit...).  Once I did that, they appeared fine.  However, upon closer inspection, I found a very small hole in one of the diaphragms.  I'm talking pinhole size.  How much of an affect could a small hole like that have?

I haven't been blessed with a pinhole leak in the diaphragm, but have read that it does need to be replaced.

Your first description (idle screw doesn't seem to behave right, and RPMs hang after twisting the throttle) sounds like a lean condition.  That would be the case if you had reassembled the carbs without that little o-ring.  You could also get a vacuum leak where the carbs meet the engine; try spraying WD40 there, and see if the engine RPM speeds up.  Another place is a cracked vacuum hose from the carbs to the fuel petcock; or a missing cap on the carb vacuum port.