Can't start 89 GS500

[jessgonz]

I have a GS500 that sat for a long time. The bike has 7000 miles on it. Went over the bike and got it running.  But it only ran on one cylinder. Sat for a couple of weeks and startd again.  It ran beutifuly on both cylinders!  Turned it off. Could not get it started again. Tried over a couple of days. Rebuit the carbs (they needed it anyways). Now the bike starts but runs poorly and when I give it gas it backfires and wants to stall. Took the carbs off and rechecked my work. Can't find anything wrong.  The bike is in great shape!
Any sugestions?

Thanks, Jess

[Suzuki Stevo]

Fresh gas?

[jessgonz]

yes fresh gas

[skirecs]

well if it ran great, and then you rebuilt the carbs and now it runs like crap, its probably in the carbs

check for vacuum leaks, the little o rings above the diaphragm, the balancing ports, the petcock vacuum hose, the airbox to carb and carb to engine hose clamps

maybe forgot to set idle mixture screws appropriatly

its gotta be in there somewhere

[The Buddha]

Yea rebuilding carbs on a bike that didn't leak gas out the carbs is a waste of $. WTF is rebuilding anyway ... putting O rings in it, so why not call it O ringing carbs. 
My bet, you mis adjusted something - the tank petcock open ? you put in prime for a few mins to fill the bowls ? Crap in the tank now worked into the carbs cos you removed the tank and disturbed it ?
Cool.
Buddha.

[mach1]

did you turn the valve on the gas tank back on? on an 89 bet you got rust in your tank.