Petcock question 1983 kz750

Hi,
so I have issue with Carb Vents leaking gas when petcock was on RES and bike didn't run.
Went and switch petcock to OFF and still some gass went through.

Any idea..?

alzo wrote:

Hi,
so I have issue with Carb Vents leaking gas when petcock was on RES and bike didn't run.
Went and switch petcock to OFF and still some gass went through.

Any idea..?

Unless you have an aftermarket petcock, there is no OFF position.  The stock petcock is actuated by vacuum, and any time the engine is off, no fuel should flow unless the petcock lever is set to Prime.  If yours is flowing with the engine off, the petcock has failed.  Realize also, that the float needles should hold back the fuel regardless, although not infinitely, so if your bike is puking fuel out the overflow tubes, most likely the float needles are fouled, and the carbs need a proper rebuilding.