Petcock leaking but can't tell from where???

I have noticed lately that my fuel petcock leaks, but only when it is open (this is on a '78 KZ750 Twin).

Gas will drip off the bottom of it, I have looked at it very closely and I really can't seem to determine exactly WHERE the fuel is coming out...it is wet from the bottom of the petcock lever itself to the bottom of the drain plug (or whatever it's called) on the bottom of the petcock.

Is there an O-ring kit for this petcock, should I just go through and replace any/all gaskets and O-rings?

Fuel especially now with the alcohol added will deterioate the O rings and gaskets of the petcock on the gas tank.

I'd replace all of them because the ones you don't replace now will be the ones that leak in the future!

k&l supply makes pet-cock kits for a lot of older bikes i think z1-enterprises sell them. they are really easy to install if you don't have any luck with that try pingel they build hi flow petcocks that work very well i have 4 of them on different bikes.

Would check tightness of the sediment bowl and integrity of its o-ring seal.

Would also assure integrity of o-ring seal where petcock attaches to tank, this being the o-ring between the petcock and the male-threads from tank. The factory o-ring is flat on both sides, however, a common round style o-ring will suffice provided it's the correct size. The o-ring fits in a groove inside the large nut which squeezes the petcock against the tank fitting, and the o-ring is supposed to seal against leakage at this juncture. A loose nut or failed o-ring may allow leakage over exterior of petcock.

Would also disassemble petcock and check for damaged (scoured) interface between plastic valve and inside surface where it twists back and forth. I suspect grit from inside the fuel tank may cause such scouring.

And also check the o-ring around the lever.

Replacing the plastic valve might help (if lucky enough to find that item ). And my efforts toward restoring an internally scoured interface have woefully failed .

Good Luck!

ghunt81 wrote:

I have noticed lately that my fuel petcock leaks, but only when it is open (this is on a '78 KZ750 Twin).

......

Is there an O-ring kit for this petcock, should I just go through and replace any/all gaskets and O-rings?

You can get a "petcock rebuild kit" for this petcock from ebay or places like z1enterprises.com. It consists of about 3 or 4 o-rings. It will solve your problem.

i had a similar problem, the last owner told me it was broken so i bought a replacement here

ebay petcock

i sent this message to the seller but no reply can someone help me?


I HAVE A QUESTION ABOUT HOW TO SET THIS THING UP, THE LAST PIECE I HAD WAS ALMOST EXACTLY THE SAME AS THE ONE YOU SENT ME. THE DIFERENCE IS THAT MINE HAD ONLY ONE OF THE REFERED OUTLETS {THE LEFT ONE I THINK }(" look it does have the two outlets that you need") AND REFERING TO THE PICTURE YOU HAD IN THE AUCTION THE WHOLE ABOVE THE OUTLET WAS OPEN NOT CLOSED.

SO THE TUBES I HAD CONECTED WERE ONE TO THE SIDE HOLE AND ONE TO THE OUTLET, AND I'M NOT SURE HOW IT GOES ON YOUR PIECE ONE TO EACH OUTLET NOT MATTER WHAT?

I'm not 100% on your question, but if you have 2 fuel lines going to your carburetors, one going to a T fitting between the 1-2 carbs, the other to a T between the 3-4 carbs it doesn't matter which fuel line goes to which outlet on the petcock on the manual petcock. This was the way it was done on the Z1,KZ900, KZ1000 up till 1978 and the 1000LTD through 1980. If you only have a single fuel inlet on your carbs between 3-4 carbs like used on the 79-80 KZ1000A-E, KZ650 ect, then you need to run that to a T fitting then two short pieces of hose to each outlet on the petcock.