Finally stopped the culprit - fuel petcock leak

[davexz]

After finally stopping a leaky fuel petcock I thought I'd tell others in case they have they same frustrating problem.  I tried a new rebuild kit and different valve bodies, cleaning, bonding the press fit connection, different washer at the drain screw, etc. and nothing worked.  I found it to be leaking around the perimeter of the rubber diaphram/plastic spacer stack up.  Studying it, I see what the problem is - the leak is coming from the chamber where the diaphram shut off plunger is.  There is a very low rib on the plastic spacer that is suppose to compress the rubber diaphram against the valve body around the plunger cavity.  Problem is - everything is too tiny and the tolerances, warping or whatever don't let if seal very well.  What I did was to double up the rubber thickness in this seal area only (looks like an egg shape seal area if you look close).  I used an old diaphram and cut out a dougnut shape and slipped it over the plunger so you have double rubbber thickness - don't include the double thickness at the 4 mounting holes because you want it to squeeze there.  It worked for me - even with a full tank of gas and after a ride. 

[QBS]

Please post some pictures, if possible.  If not, thank you for the write up.

[davexz]

Here is the only picture I got.  If you look close you can see another pear shaped piece of rubber I slipped over the plunger.  You can also see the pear shaped impression in the rubbber caused by the small raised geometry in the plastic spacer.  This is the same thing that suzuki uses to seal float bowls with a flat gasket, except they use a bigger rib and thicker gasket.  Here it is all too small to work consistently.  Hope it helps someone else.

[Tommy]

I guess that helped me - ran into the same thing today - Thanks!

[Kiwi]

What problems will a leaking petcock cause? besides a waste of gas

[Tommy]

Fire hazard? Pollution?

[Lucky]

you won't get as far when trying to escape zombies either...

[The Prophet of Doom]

  I used an old diaphram and cut out a dougnut shape and slipped it over the plunger so you have double rubbber thickness - don't include the double thickness at the 4 mounting holes because you want it to squeeze there. 

If I did that to one of my wife's diaphrams she'd never let me touch her again.  Surely there are other sources of rubber that would cause less domestic friction

[Rikugun]

You're wife is smart. The last thing we need is another little Roro running around!    :o :D ;D :)

[Rick G]

I have an old Suzuki savage (two stroke)  petcock . Its very similar to the Vision one , except it doesn't have a automatic shut off and the flange is thinner. if I have significant problems with mine I'll use it.

[Rikugun]

If you can believe this fitment chart the '82 Vision petcock rebuild kit works on a whole lotta' bikes.

http://www.oldbikebarn.com/Kawasaki-KZ440-750-Yamaha-XJ-XV550-920-Petcock-Rebuild-Kit?sc=12&category=74274

This kit would be incomplete at best for the '83 but they have it listed too. I guess this is a common mistake with petcock rebuild kit application charts?

[Rick G]

The '83 petcock is like nothing else I've seen . I think that after market suppliers assume a lot!

[Protonus]

What problems will a leaking petcock cause? besides a waste of gas

If it's leaking back into the vacuum line like mine was, it can cause all sorts of driveability problems, backfiring in the intake, blowing out your valve cover gaskets, etc.   

[Lucky]

If you can believe this fitment chart the '82 Vision petcock rebuild kit works on a whole lotta' bikes.

http://www.oldbikebarn.com/Kawasaki-KZ440-750-Yamaha-XJ-XV550-920-Petcock-Rebuild-Kit?sc=12&category=74274

This kit would be incomplete at best for the '83 but they have it listed too. I guess this is a common mistake with petcock rebuild kit application charts?

There is no rebuild kit for the 83. as far as i'm aware, i'm the only one who makes those diaphrams, I detest doing them & so they are expensive, but i do a very careful & thourough job...