petcock is hard to turn

A few weeks ago I rebiult the petcock from the 1983 kz750 and today when I was riding the bike started sputtering, so when I went to turn the petcock to reserve it was very hard to turn. I had to get off the bike to turn it. She ran good afterwards.
The petcock was turning normaly before the rebuild. Any suggestions as to what may be the problem before I go tear into it?

Yeah,

Stop using alcoholic gasoline!! It swells up the rubber parts.

KZCSI

It may lead to shortened life of any rubber/plastic part it contacts like the rubber tipped float needle jets, the floats(if plastic) and fuel lines.

Alright folks the only alcohol thats been on the bike has been on the rider. lol

Seriously, do ya'll mean ethanol blend gasoline. If so thats about all I can get is the 10% stuff. I been using premium gas on the bike and its been running fine except for the fuel petcock.

Presupposing this regards the oem vacuum operated petcock, and not a replacement non-vacuum (manual) petcock.

Am thinking that turning resistance of a vacuum operated petcock lever is mostly governed by the wave washer and rubber o-ring, and not much else, unless the valve gasket is damaged.

Was the o-ring replaced with a fuel-resistant variety?

Would check for damage to wave washer and/or o-ring, and possibly damaged valve gasket. Am thinking these parts are readily accessible from lever side of petcock by removing the two cover plate screws.

May want to first drain the fuel tank enough and prop up rear of tank to prevent fuel spillage.

Good Luck!

If not already done, would consider draining and removing fuel tank, removing petcock and inspecting the filter screens that go up inside the tank.

Damaged screen could allow grit or crud from inside the tank into the petcock valve gasket area.

May also be a good time to flush out the tank with fresh clean fuel. Just swish it around inside the tank and dump it out through the fuel cap.

Btw, would also install an in-line fuel filter if not already fitted.

Good Luck!

When reassembling the petcock, could use a little silicon lube on the wave washer (both sides) and on the lever o-ring to ease turning resistance and help avoid damaging the o-ring.

Good Luck!

Thanks Patton, the petcock is the oem and the o-rings are for the petcock per Kawasaki dealer. There is a fuel line filter installed.
I'm fixen to go take the tank off and flush it out as recommened and check the filter screen.
I really think lubing the lever o-ring id going to do the trick though.

I used silicon lube sparringly on the 10mm (not quite remember size) o-ring and it solved the binding issue I had as well. I also bought my o-ring from the Kawasaki dealer but it tends to swell a little from the fuel and then started to bind when you turn the petcock. They do not sell the mesh filter (unavailable) so I put in an in-line fuel filter. Good luck.

hey folks,
My petcock on a 76 900 was getting hard to turn also and the other day it became super easy to turn while riding(then the bike died).
i took it apart to find that i had snapped the male groove off of the back of the on-off-reserve-lever.
i should have lubed the thing inside!!!! and i would not be on a mission to find a new petcock lever.
anybody know where to get just the lever for replacement.
i am off to the ;local shop to see what they got in backstock.
i also bought and installed a cheaper petcock from z1enterprises.com last week and it came with a torn three hole gasket inside as new and never would shut off.the guy i talked to there said they have had this problem once or twice and was sending me a new diaphram ..he was really good about it.
what is the story am i needing to watch who and what kind off fuel i purchase...peace craig

Hi Craig,

There's only one place in my home town where nonalcoholic gasoline is available and they won't put it into a street legal vehicle.

I know that the fuel petcock on my 1976 KZ900 will get harder to turn if I put alcoholic fuel into it. So far all that I've needed to set it right was a tank of straight fuel.

I'm not suggesting that it's necessary to go to special fuel to avoid the problem but many older bikes will have trouble if they still have the OEM rubber parts.

I think the alcohol proof rubber is "nitrile".

Bill R

I took the tank off and gave it a good whirl and dumped the gas out (and all over the tank too)lol.

Took the petcock off and checked the screen and it was clean. Lubed the o-ring that's inside the lever and it's working fine for now.

When I was installing the 2 screws that hold the lever in I accidently stripped one . I guess I will have to look for another petcock anyway. dang it.