oh yeah i was having problems with my petcock also. It was leaking into the carb through the vent side, and filled the crank case with gas when sitting. I just plugged that side and it runs fine

 

I had the same problem with my ride i thought its was à carb problem but it was my regulator ,it was delivering 18v ,so to make sure it was the sole problem i disconected the regulator connector(2 red and 2 black wires ) and took a test ride everything work fine so a change of rectifier/regulator did the work for me ,the electical act eradic when given too much juice.