LEAKING PETCOCK

What you can try is to remove the vacuum line & cap the vacuum ports with good automotive vacuum caps,
then ride the bike with the petcock set to PRI. When the engine is stopped, switch it back to ON.

ON & RES now function as OFF, and PRI functions as ON. Keep in mind that you won't have a reserve, so don't run out of fuel.
The diaphragm o-ring needs to be good and I would check & buff the o-ring mating surfaces.
That o-ring needs to fit the orifice snug, so the diaphragm spring needs to be good as well.

The man I bought bike from sent me the oem rear upper fender. Well along with it was a OEM in the box petcock rubber diaphram gasket. All I have to do is change it now. I do have another question on the petcock. Which setting is off?

There is no OFF with a vacuum petcock.
Do yourself a favor and rebuild the petcock properly. This is a good tutorial...
Petcock rebuild
It's for a XS650 but applies to all vacuum operated petcocks.

This guy has all you need, non vacuum/vacuum repair kit and petcocks.

z-fever.de/shop/index.php?cat=c324_fuel-...fuel-system-324.html

OK let me try to explain what I went through. When I got this bike it seemed like it would not rev. Was lazy feeling. then the petcock started leaking gas. The power then went up to like it should be. Good running plenty of power. I had put rtv on the spot it was leaking and it stopped. Bike run well. I was concerned that maybe fuel could get into crankcase if the diaphragm was busted. So today I took the OEM diaphragm I had in the box and repaired the petcock. Not leaking but NO power!!! Runs like it did when I first got it. No doubt its not getting enough fuel. I have ordered a manuel petcock and will be changing when it comes in. I guess something to do with enough vacuum must be the problem. I know I got the diaphragm in correct and installed right. Does this mean the petcock is not getting enough vacuum to open the diaphragm????

It turned out the petcock was not the reason the bike was missing it was carbs. I installed the petcock off of e bay it it works like a champ. Appreciate all the help. sorry for the confusion. Im learning here for sure.

GS963 wrote: this is one I ordered off of ebay

What is your opinion on this part? I'm looking at one of these for my kz1000p.

GS963 wrote: It turned out the petcock was not the reason the bike was missing it was carbs. I installed the petcock off of e bay it it works like a champ. Appreciate all the help. sorry for the confusion. Im learning here for sure.

As others have suggested, repairing the vacuum petcock is the correct route. A manual petcock is more often than not, a PITA and forgotten to either turn on OR turn off,. You go to start your bike and it it is sitting in a puddle of fuel with the possibility of >flame on< if anything sparks. It appears it was already mis-diagnosed as to being the cause of cutting out, when in fact the carbs were plugged from crap. The first thing to learn, is that the bike doesn't run very well on contaminated fuel.

If you rebuild the petcock with the proper parts, and polish the seat that the o-ring seals on it will work flawlessly for a long time. This goes without saying, the tank also needs to pe perfectly clean with fresh clean fuel in it. Doing these basic things saves on a LOT of guesswork.



it is usually best not to try to re-engineer things that teams of engineers already figured out for you.