Replaced gaskets on petcock, made leaking worse!! - Motorcycle Forum
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Old 04-23-2009, 11:30 AM   #1
SkinnyDave
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Default Replaced gaskets on petcock, made leaking worse!!

Original petcock on 1983 750 Maxim... Before it was leaking from the square back plate (vacuum valve) i THINK... though it's really difficult to tell with gasoline in a tiny cranny like that. It just started leaking a few weeks ago.

I was in the process of sealing the tank from rust so I bought new gaskets/valve rubbers for the petcock while I had the thing off.

I replaced the internal rubber of the thing, and also the O-ring that seals it against the tank. But now it's leaking from its seal against the tank.. or maybe from EVERYWHERE.. I can't tell... but when I get that thing on there tight, making sure the gaskets are fairly square, no chunks of debris in the way, and turn down the screws TIGHT... it still leaks like a bloody nose... from the top.. I mean the whole thing is covered in fuel and dripping willy nilly. Needless to say my driveway was a bit of a fire hazard last night

Is this an issue like ... I gotta let the thing sit in place for a day or two before the gaskets "mold" into place and "seal up"?? or is it just that dodgy trying to repair a petcock?? Anything I can do?

New one is $125 and I wouldn't really trust one from ebay...

The weather is getting SUPER beautiful and I'm almost reduced to tears cause I can't ride. I've been wanting to skip town on my bike for WEEKS and I've had to deal with tons of ridiculous bullplop like this.

thanks
-David
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Old 04-23-2009, 08:47 PM   #2
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I hate Yamaha petcocks. They belong in the trash, good riddance. Got myself a Yamaha adapter plate which takes a standard threaded petcock, and of course a universal manual petcock to go with it. Nice thing about the adapter plate is you can then buy any inexpensive and easily obtained 3/8" NPT petcock you want. I got an earlier version of the petcock shown here: https://www.partsnmore.com/cat_index...&category=carb. It's been trouble-free for a couple of years now, I'm very pleased with it.

I'm not sure if all Yamahas take 46mm adapter plates, they probably do -- best to double-check if you're thinking about getting one though. FYI you will have to Dremel out a little bit of metal from your tank's petcock opening, I filled mine with water during this operation to avoid a minor gasoline explosion.
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Old 04-24-2009, 06:53 PM   #3
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Whoa thanks!!!! This should solve the problem rather nicely.

Though, I notice that this is a simple non-vacuum petcock. Does that mean it simply relies on the float needles to stop fuel flow? Also, what positions does the valve have? Just on/off? Hopefully there's an "off" for when you disconnect the hose

BTW, I managed to solve the leak for now!! GOD I'M STOKED!! NOW I CAN RIDE. All I did was replace the (brand freaking new OEM, ahem) O-ring that seals the **** against the tank with the old one.. I put the original one back on there, which had crud stuck to it! But it wasn't the o-ring that was leaking originally, so apparently it was still good enough for the task at hand. (and not the freaking new one I spent $$ on .. thanks Yami)
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Old 04-24-2009, 06:54 PM   #4
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um.. that "****" up there was just the word petcock minus pet ... hahaa .. oops...
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Old 04-24-2009, 08:06 PM   #5
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Quote:
Originally Posted by SkinnyDave View Post
Though, I notice that this is a simple non-vacuum petcock. Does that mean it simply relies on the float needles to stop fuel flow? Also, what positions does the valve have? Just on/off? Hopefully there's an "off" for when you disconnect the hose
There's Off, On, and Reserve. I turn mine Off after every ride and On before, but I suppose you could leave it On all the time if you trusted your float valves.

Glad you got yours working though...
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Old 04-25-2009, 12:06 PM   #6
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cool, thanks
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