Vacuum Petcock

I have a '78 KZ650 and the petcock on it is vacuum operated and is supposed to let the fuel flow in the on position only when its running right? However when i disconnected the fuel line from it while it was in the on position, fuel flowed freely through it and it made taking the tank off a really big pain in the ass. I tried the Prime and Reserve positions too and it didn't matter, the fuel still flowed. Can it be disassembled, cleaned and rebuilt to fix it or should it be replaced? Any help is very much appreciated!

Yes, it can be repaired with a rebuild kit. While that should fix the problem, it's no guarantee. I kitted two and both started leaking from where the elbow goes into the petcock main body. I gave up and bought the Pingel adapter plate and cheap manual petcock from Z1 Enterprises and have been pleased with the results. It does require some filing to the tank as the new petcock is round and is larger than the stock tank opening. The vacuum port on the #2 carb is then plugged off.

BTW, welcome to the forum.

Kawasaki still stocks the OE petcock, at least for the 1000. Over $100 though.

You can buy the diaphram kit for $10-$15 and will fix this problem every time. Don't bother dissassembling, trying to clean ect. It won't work. New one works every time.

This petcock repair kit from Z1E should correct the problem.

Click here > Petcock Repair Kit

Z1E also offers the diaphragm alone > Diaphragm .

I would recommend using the full kit instead of just the diaphragm alone, especially where any doubt exists as to exactly which component is responsible for the leak.

Good Luck!

Save your self a lot of time and trouble just go ahead and buy an after market petcock and the pingle adapter.then when you turn it off its off.might also kep you from getting a crank case full of gas!

If I was gonna spend $100 on a petcock it would be a Pingle. High flow, smooth as silk , reliable as a spoon and big bling factor.

Like the little girl with the little curl, 650 vacumn petcocks are either very good, or shitty. the fat oring on the face of the diaphram #26 is failing to seal. whether problem is petcock body, diaphram, spring, or check vlve in diapham plate is your' guess. I've tried 6 or 7 rebuild kits, w/@ 50% success. If there is an accessory manual petcock, or oem (early model OE or other ) petcock which bolts up, I would go with it. Vm carb float valves meter fuel pretty well in running, but are poor when sitting with a 4-5 lb presure head. luck G

You can bolt up an original 1977 KZ650 manual petcock, but it's the same thing as replacing an electronic ignition with points, it's not worth a crap in the long run. Put the diaphram on and do it right it will work 100% of the time.

Sorry, Ron. 100% is far too optimistic. 25 to 30% is more realistic and perhaps still far too high. Too many of these bikes were neglected along the way in their previous lives and the petcock body is just shot.

A more reliable fix can be found at Z1 Enterprises . To the OP, measure the mounting holes center-to-center, buy the correct adapter plate, and the $13 petcock will will work just fine on a 650. I've done three with no performance issues.

Yep,
what NONB said.
I tried rebuilding several OEM vacuum petcocks and had 0% luck ZERO. Time and corrosion take their toll on these parts.
I Switched to the $12 Pingel with $12 adapter plate, and no problems since. Off is off, on is on, you just have to remember to turn it manually.

Well I'm still at 100% luck rebuilding, but only done about 5, but 5 out of 5 aint bad.