Suzuki 2 Strokes

Using a 1972 GT380 petcock with three outlets. Cleaned it up & am using new lever & float bowl gaskets.

Using a new Kawasaki H1 diaphragm kit.
The kit includes the little rubber washer for the diaphragm vent — its a slightly different size the the original Suzuki part.
The kit washer doesn’t seal correctly & gas pours out of the vent when the petcock is flowing.
Switched back to the original washer, which stopped the leak at the vent.
Tested the petcock with a little hand vacuum pump & its working fine.

The diaphragm slowly weeps gas around the mating surface where its screwed together.
Do you need to put a key onto the petcock surface so the diaphragm seals? And what would that mean?
Or what else?

You've got me. The kit should work. If not it's a bad kit,,,,,,,,,,,,,,,

I have it fixed.

I used 320 grit sandpaper on a flat surface to give petcock surface just a bit of key. Only did the wet side.
Lightly tightened the diaphragm screws & installed the petcock.
It barely leaked a smidgen so I tightened it a bit more & its now fine.

Perhaps some residue from the old diaphragm prevented a proper seal with the new one & sanding eliminated the residue.

The H1 diaphragm + o-ring worked fine.
There is a little air vent in the diaphragm chamber. Its sealed with a little rubber washer. The OD of the washer in the kit was just a little too big but that wasn’t a problem because the original one was fine.