Left plug rich, black and dry, right plug lean, almost white.

[commuterdude]

Might have a faulty petcock on the frame/ vacumn to left carb?  How to check?   Took the carbs down and cleaned em up, believe I got them clean ok and put back together ok.

Are petcocks expensive/available?

Bike cranks and idles, adding choke revs it up, no choke bike idles low and a little lumpy, dies on occasion.  Adding any amount of throttle bogs it hot or cold.   Adding throttle when the choke has the revs up around 5-6000 doesn't kill it but it makes an odd sound, like it might be running on one cylinder, sort of an off tune chugging sound.

[ben2go]

Have you set the float levels and balanced the carbs?Petcock will not cause 1 side to lean out.Have the valves been adjusted?

http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/FloatHeight

http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/5CarbSync

http://video.google.com/videoplay?docid=-2015554469142545363&q=suzuki+gs500

[commuterdude]

No, no, and no!   arghhh, tank must come off again.   Just gonna get new lines and put them on too.

But what is this I've been reading about the vacumn to the left carb from the frame mounted petcock?  Would running in prime bypass the petcock vacumn essentially?
Reason being is that it runs the same in prime pretty much as far as I can tell.

[ben2go]

No, no, and no!   arghhh, tank must come off again.   Just gonna get new lines and put them on too.

But what is this I've been reading about the vacumn to the left carb from the frame mounted petcock?  Would running in prime bypass the petcock vacumn essentially?
Reason being is that it runs the same in prime pretty much as far as I can tell.

Yes running in PRIme bypasses the vacuum diaphram internally.The Internal PRIme orifice is very small and will led to fuel starvation at sustained speeds and high rpm.You can convert the petcock to eliminate the vacuum or get a cheap replacement.

http://gstwins.com/gsboard/index.php?topic=19363.0

http://gstwins.com/gsboard/index.php?topic=36958.0

http://cgi.stanford.edu/~sanjayd/gs500/Main/HoseRouting

[commuterdude]

Didn 't have the vacumn hose to the left throttle hooked up to the petcock.   Hooked it up thinking YAY, but while the rev's w/ choke are higher and faster, adding any throttle still bogs her down immediately.    Gonna go back into the carb and check the float, re clean, get all new hoses (they really need it), and rig up a TEST GAS TANK.   Gone to the beach for a week first to think about it.   Ya'll have a nice day.