I think the petcock is bad on my new to me 94 gs500.
If it is on "ON" it dies...it runs on "res" but boggs and restricted..it runs on "pri",but it boggs down at low rpm only takes off over 8000 rpm.
Is the petcock bad ? or do the carbs need cleaned?
-CS

I'll bet you a case of beer that a vacuum line is either not hooked up or hooked up improperly.

no the vacuum ,and all 3 fuel lines are new,and hose clamped.
Too bad I'm not a drinker
-CS

The bike starts up in 1/4 sec ,and runs idles perfectly..the throttle is blah from 1000-5000 rpm and really dont fire up till 8000.
-CS

Today I could see air in the fuel line.
I switched the fuel chicken to other positions ,and it seems that BETWEEN ON ,and RES is the only way fuel flows through the clear hose. 
It still ran like crap from 1000 rpm to 8000 rpm.
-CS

This bike sat from 2001 to 2012......im sure with no PM b4 storage.
I will have the carbs cleaned ,and update.
-CS

Hell. If mine sits over the winter without being ran i clean the carbs. It's likely that the o-rings in the petcocks (yes, both) are bad, allowing air into your lines. This would solve the air bubble problem, or at least it did for me. And clean/rebuild your carbs. Replace anything you can.