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  Topic Review (Newest First)
07-29-2017 09:32 AM
mrseedsower The Yamaha petcock is a TW200 and I got it new from the Yamaha dealer for less than $40
07-29-2017 09:24 AM
mrseedsower I went round and round with a leak with my petcock. I had actually two leaks. One on the outside and one on the inside that caused it to leak into the cylinder.

I solved mine by putting a non vacuum petcock on the bike. I believe it was a Yamaha petcock and I haven't had anymore problems since.

So if you want to get past a headache fast that other petcock is the way to go.

07-24-2017 01:24 PM
twowheel82 There is no gas in the crankcase for sure. The diaphram does not look as if it is worn or that is was ever in the groove . It does not affect the way it runs or performs.
07-24-2017 01:20 PM
Spockster I do recall a notch or groove on one side when I rebuilt mine last year.

More than likely the diaphragm is leaking vacuum, it may also be leaking fuel through the vacuum line, which can fill the crankcase with gas.
07-24-2017 12:47 PM
Petcock vacuum leak

My wife has a 94 750 Great bike. There is a vacuum operated petcock with a leak that I can put my finger on it. It is at the bottom back corner. I took it apart and there is a groove machined into the back cover where the vacuum leak comes from. No one I talk too knows if is supposed to be there or if I need to get a rebuild kit. Anyone out there know Please and thanks for your help

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