Bike wont idle!! Will rev with throttle but then dies.

[tom42]

I have a '91 Gs 500 with 6000 miles on it.  Last year I the bike would die on the highway.  I changed the petcock with a used on and it was OK.  Now, without warning, it died on me and will not idle.  Is this another petcock fuel starvation situation?  Can I just buy a new '09 petcock and rig it to attach to my '91, plug the vacuum on the carb?  Or is this something else i.e. jet needle, dirty carbs (I only use high octane), something else?  Any help would be greatly appreciated. In the mean time I an going to try another '91 petcock I have lying around.

Thanks

[jeremy_nash]

high octane gas doesn't do the gs500 any good, but it wont hurt it either.   if you go with a petcock off an 09, you will still need the vacuum line.  does it run if you set the choke to on?  I would guess that the pilot jets in your carbs are clogged up, since you said it revs fine, but wont idle

[tom42]

I did rebuild the carb about 2000 miles ago because it sat for about 4 years.  I guess I will check that when it get it all open

[kylegod]

my bike would only idle if i held the throttle. tight exhaust valve did it. now it idles perfect. valves done recently?