Vacuum Petcock rebuild kit - FAIL

While we're all here I DO NOT use aftermarket petcock 4 hole rubber valve either, Yamaha sells the correct part, the aftermarket are thinner.

@gggGary alluded to a work around/fix in my thread maybe he will expand on it.

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I take no responsibility for this working for you.
Went and looked, sure enough had an unopened K&L kit from the infamous cardboard box of parts that comes with every project bike.
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The suspect
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grab an 18mm-ish socket, stuff the diaphragms inside so the disk contacts the socket edge.
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Gently tap the end of the shaft til the disk takes on a slight dish shape,
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it's aluminum will bend easily. You only need a 1/2 mm or so. This effectively lengthens the shaft causing the o-ring to contact the seat a bit sooner. Check the disk is still at 90 to the shaft, the edge even.
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It will be happy to warp, get all ugly if you overdo the tapping. Done.

IIRC correctly this fix has been in use on Madness' petcocks for ten-ish years.
Carry on!
It appears that @gggGarys fix is as good as it gets, what he is doing is making the valve longer. I would prefer to use the old valve if still good.
I went with the ebay gravity model. I couldn't get the oem tap put back together after i took it apart. Gravity one works great. I am using the one that has 2 outlets, one side has a bolt screwed in. I am using both sides and the set-up works great with the new VM34 carbs.
My XS650SH has been sitting with the tank dry since early November. It’s end of January. It was empty to repair a leak at the fuel cap seal. Friday was a pleasant 62F. I put gasoline in it. I rode it seven miles for E0 fuel.


What a PITA. It leaks with the fuel ON. No leak OFF. It appears to be leaking from the body. I put a rebuild kit on this late spring and got 3,000 miles out of it. I believe I’ll focus on fixing the vacuum petcock. The aftermarket unit looks and acts like poor quality. It was too much effort to get it to work in the first place.
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Very unfortunate. I do understand the frustrations of a leaking fuel petcock because of all the work it takes to deal with the fuel tank.
My left vacuum petcock body leak after replacement of the plunger O’rings (which was a success) frustrated me enough to try the manuals. Only minor flattening of the valve and installation.
I’m lucky 🍀 mine are so far performing perfectly.