TOPIC:

The petcock on my 1980 KZ440A (LTD) doesn't seem to be flowing any fuel when the bike is running. If I start the bike and ride, it'll die after a few minutes, but I can set the petcock to Prime and drive it all over without issues. Is this a failed petcock? I thought they ususally failed "open" such that when they fail they leak gas into the carburetors.

Would check integrity of the vacuum hose from carb to petcock.

It's the vacuum being supplied to the petcock that's supposed to enable fuel flow through the petcock when the petcock is set in the ON or RUN position.

Where vacuum is being supplied to the petcock, but fuel still isn't flowing through the petcock as it's supposed to, the petcock might be clogged internally whereby normal operation of the spring-operated diaphragm is obstructed with grit, sand, crud or whatever. Sometimes the condition can be remedied by disassembling and cleaning the petcock internals. Other times, replacement of some internal parts may be necessary, in which event petcock repair kits are usually available through suppliers such as Z1 Enterprises.

Good Fortune!

Thanks! I took off the gas tank and hooked up a vacuum line to the petcock and tried sucking on it. I get a couple drops of gas, but not a lot. I also replaced the vacuum line at the same time, just in case. I think I'll try taking it apart and cleaning it next; hopefully that helps.

Take it apart and rebuild it. Do it right and it will last a good long while...
Rebuilding Vacuum Petcocks