Vacuum actuated petcock does not stop fuel.

You have to keep an eye on the oil.. Gas can fill up in your crankcase. A few around here have had the problem. Mine would fill up overnight. I'm sure it took a few miles out of the motor..:blink:

Is the spring in the correct position?

I have had the same problem, but successfully rebuilt my petcock.

I also went to the dealer and got the different diaphragm which did not cut off the fuel. I think this new diaphragm is worthless, and the o-ring seems to be too small for the KZ650 petcock.

What did help was replacing the rubber bit on the other side, #11009B and going back to the original diaphragm + replacing the spring. I think the rebuild kit came with a new spring.

Anyways, the diaphram and that weird rubber thing are all the seal the petcock internally, so if it isn't stopping fuel when there's no vacuum, try to figure out which one it is.

What I also did was make sure there was a good surface for the diaphragm to seal against, so I smoothed out the body of the petcock where the diaphragm seals against.

I did about the same thing, butting the original boot back in.

This evening I opened the oil fill plug and all smelled well, check the spy glass and the oil is at the same level as when I changed it a few weeks ago. I unscrewed the drain screw at the bottom of the petcock and fuel filled a soup can before I tightened it up… so I still have the problem.

I am taking the “Class” this weekend, and helping someone put the heads back on a 351 at night. In my “spare time” I will try to take the petcock apart again and see if I can’t get it to seal, maybe next weekend.

Willie, at one time, petcocks were simple affairs... they turned gas on and off. Some owners didn't have a good memory and forgot to turn off their gas supply when parking the bike and found a puddle under their bikes. One may have lit a cigarette because the manufacturers decided that gas turning-off was too hard for the average rider so they came up with vacuum actuated petcock. These work GREAT until the added complications of rubber bits and diaphragms find the vacuum petcock failing and allowing gas to drool while the bike is not running.

The BEST answer is to install an old on/off petcock and remember to turn it off when not operating the bike.

Measure the offset between the mount bolts on your petcock. On my KZ1000E1, they are 44m apart. In any case, armed with the bolt offset, buy a $20 Pingel adapter plate from www.z1enterprises.com . They also sell $20 Drag Specialties petcocks that are ON/OFF (and have a RES function which means reserve). These petcocks are fully rebuildable and are simple and don't leak. I have them on all my bikes; some of which were equipped with vacuum petcocks. Don't forget to put a vacuum plug on the carb spigot that had been providing engine vacuum via a hose to the carbs. For $40 you actually turn your gas off!