I spent Sunday and Monday working on my bike.  It's now going great again!  I wanted to pass along a problem I found because it probably exists in lots of older GS500's out there (mine is a 1998).  If you have fuel coming into the airbox, or fuel dripping out the carbs, read on!

The carb float bowl seat (of the inlet needle/seat set) is held in by ONLY the friction fit of an o-ring.  When old and compressed, the o-ring no longer seals, meaning fuel goes AROUND the needle and seat.  No setting or re-setting of float level will change the overflowing condition.  Only replacing the o-ring will fix that problem.  I found the o-rings at the local O'Reilly's Auto Parts.  Needles and seats are almost $40 for each carb, and I did not need them once I resolved the o-ring issue!

I had been seeing a problem of a float bowl overflowing, and it got so bad that it was fouling the left plug and stalling at idle.  I finally had time this weekend to attend to the problem.  I removed the carbs and began trying to set the float level.  Numerous tries produced no change in the left carb, so I assumed I'd need a needle/seat on that side.  

I decided to swap the needles/seats to see if the problem followed the needle/seat to the other carb.  As I pulled out the seat on the bad side, it was almost loose in the carb body - not at all like the side which was actually working.  I took the carbs and seat down to the parts store and found an o-ring that fit perfectly.  Now I only had to set the float level.  I'm a little anal-retentive, so I did several tries before getting it just where I wanted (using a clear line coming out of the drain and held alongside the carb, I wanted the level even with the bowl cover seam).

Next, I checked the valve clearances -- all were good.  Then I wrestled the airbox for a good half-hour getting it re-installed.  

For the record, here is the preferred method of installing the stock airbox (a ROYAL PITA no matter HOW you do it)

• the petcock MUST be removed to remove and install the airbox
• check the alignment of the airbox-to-carb boots - there is a tab on the top of the boot that should align between two raised dots on the airbox,
• put carbs on the airbox (with the air filter removed, use your fingers inside the airbox to help guide the rubber boots over the carb velocity stacks),
• tighten the airbox-to-carb clamps,
• starting with the carbs angled down, wrestle the airbox and carbs into place, swearing and sweating profusely
• tighten carb-to-head clamps

Finally, I changed oil and filter, since some gas had undoubtedly made its way in to the oil when I last rode the bike with overflowing carb.

A 100-mile ride capped off the day and the bike ran GREAT.

hhaha, yea dude thats why they make rebuild kits with new needles and seats in em. those and carb gaskets for like 20 bucks man. lol nice discovery though.

I didn't see any rebuild kits with needles and seats for anywhere near $20.  Post a website and I'll buy some for later!

You take a painful approach to the airbox. I've had mine in and out several times without messing with the carbs at all. Helps to take the aircleaner out so you can fiddle with the carb boots from the inside. Petcock stayed on the frame, too. It's snug, and some swearing might have been involved, but you are making it way too hard on yourself by doing it with the carbs on it.

yea i can the airbox out without touching the carbs too, leave them alone next time. as for the petcock, i always take it off cause unscrewing one 12 mm bolt in easy access is worth it for to not have swoop and swerve my box around it. heres some links but theres plenty more. just google motorcycle carb kit make sure you check the year cause not all years are the same

http://www.bikebandit.com/k-l-economy-carburetor-repair-kit?mg=3614&t=1&td=1

http://cgi.ebay.com/ebaymotors/2-SUZUKI-89-00-GS500-CARB-KITS_W0QQcmdZViewItemQQhashZitem2eaa80c9f8QQitemZ200429062648QQptZMotorcyclesQ5fPartsQ5fAccessories

http://www.oldbikebarn.com/Carb-Repair-Kit-Suzuki-GS500-04-06?sc=2&category=126

gregvhen -- Thanks!  I had no idea I could get them that cheap.  I'm going now, since the o-rings worked, but sooner or later the needles and seats will give up.  They always do!

I left out the best part.  The parts store just GAVE me the o-rings.  They said unless I was buying a bunch, it was not worth messing with.  Of course, they get plenty of my money for other stuff as it is...