The vacuum line on your existing petcock opens the valve automatically when the engine is running and closes it when the engine shuts off. This will keep the carbs from filling your crankcase with gas if a float valve doesn't seal.
The petcocks you're looking at on Ebay are not for your bike. They're for bikes with fuel pumps (as opposed to gravity feed like your bike). The pump won't allow fuel to continually drain if a float valve goes bad, so the vacuum operation isn't necessary.
The petcocks you're looking at on Ebay are not for your bike. They're for bikes with fuel pumps (as opposed to gravity feed like your bike). The pump won't allow fuel to continually drain if a float valve goes bad, so the vacuum operation isn't necessary.
