Here's what I think is happening: The petcock uses engine vacuum created when the engine is running to pull back a small piston in the petcock that allows the fuel to flow. When the engine shuts off, the vacuum is removed, the piston is released and the fuel shuts off, even though the fuel supply lever is left in the "on" position.
The petcock diaphragm operates this piston. If it is defective, that would allow raw gas to gravity-feed to the float bowls -- since the lever has been left in the "on" position -- eventually overflowing and backing up into the air intakes, as well as draining into the crankcase. The bubbling noise you hear is probably residual accumulated raw gas in the intake being disturbed by the rush of new gas/air flow as you attempt to start the motor. I always suspect rubber parts, especially old ones, and would recommend a petcock rebuild kit. They're about $17 at most online suppliers. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
