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leaking fuel petcock

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Burro

leaking fuel petcock

I've been working on a 71 cb750k for a friend. We've gone through three petcocks 2 new 1 original to the bike. All three leak when in the off position. I've confirmed this with the tank off the bike and only enough fuel to be over the top of the reserve tube in the tank. Dripping through the brass nipples as if the valve doesn't properly seal. Any ideas this is driving me mad!

I'll believe that corporations are people when Texas executes one!

shinyribs

Re: leaking fuel petcock

Administrator

Sounds like the rubber bits inside have gone bad. I think vintagecb750.com sells rebuild kits for them.

Burro

Re: leaking fuel petcock

Thanks Shiny that's what it feels like to me too. My concern is that the current valve was ten minutes old when it started dripping. Am I doing something wrong on install?

I'll believe that corporations are people when Texas executes one!

shinyribs

Re: leaking fuel petcock

Administrator

Oh, you meant new as in new. lol. New to me often just means a different one,not an actual new part.

Hmm, I'd be tempted to contact whoever you bought the new ones from. I can't think of anyway you could possibly cause one to leak. Who's valves are they?

Burro

Re: leaking fuel petcock

Sorry should have been more clear. You might find this amusing. Both new petcocks came from vintage cb750. Are they supposed to drip? If they are that's horsenpucky!

I'll believe that corporations are people when Texas executes one!

shinyribs

Re: leaking fuel petcock

Administrator

LOL. Well, that cures that then. I'd probably contact them and tell them what's up. Hopefully they'll make it right. Might be a bad batch. It happens sometimes.

Burro

Re: leaking fuel petcock

I Will contact them. One new one was last year. Second new one this eve.

I'll believe that corporations are people when Texas executes one!

TOOLS1

Re: leaking fuel petcock

Administrator

Could there be dirt in the tank getting into them, and causing them to leak?
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
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Burro

Re: leaking fuel petcock

Tank is pretty clean. No real amount dirt or debry.

I'll believe that corporations are people when Texas executes one!

81SuperChris

Re: leaking fuel petcock

In reply to this post by Burro

Hi Burro,
I've just gone through this same problem, and busted two washers in the process. WHat I found was that I was over tightening everything, and breaking the seal - creating a leaky petcock. I went hand tight with it, far looser than I'd like, and it's completely leak free now. Might be too simple of an answer, but I thought I'd give it a shot.