A little background, first. I've owned this '89 GS since '92. This is my 5th motorcycle. Before the Suzuki, I had two Triumphs and two Hondas. Previous to the GS, the Honda 450 I rode for 20 years. All those bikes, all those years, NEVER a fuel or carb problem. In 2007, my GS just had its 3rd carb re-do; cleaning, jets, etc. Crappy fuel was alleged to be the culprit again. In 2007 the GS ran great. Stabil in over the winter.  2008, the bike ran"almost" great. Once in awhile, a bit of hesitation, but otherwise, really pretty good. Once more, Stabil over the winter. April and May this year. some very noticable hesitation across the rev range occasionally, bothersome to be sure, but I was hoping that running it almost empty and putting fresh fuel would improve matters. June and July were no-ride months because of weather and prior commitments. Riding in August was almost intolerable because of increased hesitation and stumbling all over the RPM range. Rode to allmost a dry tank and then put in 2 galllons of Shell premium and 2 oz of Stabil. After that, the bike would barely run at all. Next new plugs (the old ones looked OK and the spark seemed good as well) and 3 oz of SeaFoam. (I'm getting desperate here). Now I have  excellent throttle response from around 5K and up to redline, but the only thing I can say about throttle response from idle to about 4500-5000 RPM is that it's "same day". The only way the bike revs above idle is to S-L-O-O-w-L-Y twist the throttle. I've drained fuel from the carb floats and it appears to be clean; it's clear and debris free. All the fuel lines were replaced with Suzuki lines when the carbs were redone in 2007. All the vacumn lines are attached and don't seem obstructed.

Any suggestions? A 4th carb redo seems to me to illustrate a poorly designed and intolerant fuel delivery system for a relatively simple bike, especially by 2009 bike standards.

Thanks  for any suggestions as to what to look at next so that the throttle rsponse is crisp and instantaneous like it once was "back in the day".

Paul

clogged idler jets sounds like a good cause. the >5000 good running sounds like hte mains are ok.

is your air filter dirty ?

valve check was when ?

is your choke sticking ?

I would defer to Buddha on this topic but here's my 2 cents.  I'm in the habit of cleaning my jets, checking my valve clearance and synching the carbs every spring.  One thing I like about this bike is it only takes a Sunday afternoon to do all that and its ready for another year of riding.  Good luck to you!

-Jessie

I agree with BaltimoreGS this is a Buddha question. My 2 cents are a question? I've read several times that the pre 91' carbs are prone to float wear and need to be reset over time not mileage. So though you are doing your due diligence with the stabil every year your floats may be ageing out of adjustment. Have you ever adjusted the floats?