Early GT triple petcock with Kawasaki H1 diaphragm assembly

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jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Early GT triple petcock with Kawasaki H1 diaphragm assembly

Post by jabcb »

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?
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
rngdng
AMA Superbike
Posts: 1769
Joined: Tue Oct 14, 2008 6:47 pm
Location: Blythewood, SC, USA

Re: Early GT triple petcock with Kawasaki H1 diaphragm assem

Post by rngdng »

You've got me. The kit should work. If not it's a bad kit,,,,,,,,,,,,,,,
If you stroke it more than twice; you're playing with it.

Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
User avatar
jabcb
Moto GP
Posts: 4240
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: Early GT triple petcock with Kawasaki H1 diaphragm assem

Post by jabcb »

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.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
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