Leaky Fuel Valve on a '79 Motobecane 50V

So I was out cruising on the moped, pulled into the parking space, reached down to shut off the fuel valve, and noticed there it was all wet with the 32:1 gas/oil mix that's supposed to stay in the tank.

The valve is an after-market replacement, not the factory-installed Motobecane valve switch. It's been working fine up until now - I don't know of anything that would have caused it to change.

Any ideas, tips, advice, or otherwise?




Update: I'm now draining the fuel back into my gas can, getting all the fuel out of the tank. I had the fuel hose pointing down into the gas can, but realized there was more gas coming out of the valve itself than the hose. So I've rigged a catch-all funnel to get it all into the can.

Re: Update

Sounds like a bad rubber O-ring. Can the fuel valve be taken apart?

Re: Update

Well, I took apart the valve. It was all caked up on the inside with what looked like rust junk from the inside of the gas tank. I cleaned it out, tried it again, still leaked. Leaks even more when you push down on the center of the knob.

When I cleaned it out I did notice there were little tiny O-rings inside the valve that looked like they had broken and were not doing their job. Now that I think about it, that's probably what the problem is.

And with that much rust junk built up in there it make me think I really need to flush the gas tank of all that stuff.

Looks like I'll be driving down to Myron's Mopeds tomorrow to get a new valve.

Re: Update

Why not just replace the messed up rubber rings?

Re: Update

Yeah, that might work, but I'd rather just buy a whole new valve - the fuel filter that's attached to it looks like it could need to be replaced as well.

I've been reading on here about flushing out the gas tank of all the rust. Sounds like something I'll need to do soon.

Re: Update

Yep, my Moby tank is rusty too.. I'm going the Muriatic acid route.

Re: Update

Mike Scouty McScoutington /

you should buy an inline fuel filter as well. it never hurts to have one more line of defence for your carb. watch out when you re-run your fuel line. i had a bugger of a time re-running mine on so it didnt rub on anything or touch the cylinder and melt. an aftermarket petcock for a motobecane points your line away from the carb making it fun to run without kinking ect.

Re: Update

That's interesting.. the new petcock I bought from mopedwarehouse.com has the fuel outlet in the same position as the old petcock. Should route just fine. Are there some being sold with the outlet in the wrong position?

And I'm totally with you on the fuel filter thing. Both the petcock and the carb itself have screens, but I tend not to trust them.

Re: Update

Mike Scouty McScoutington /

if you are looking at my percock on my bike it goes out to the rear of the bike. my buddy has an original bike that the petcock points to the front. i was told by someone that the aftermarket petcocks they got and put on my bike was backwards of stock. either way i have ended up on the side of the road about 3 times trying to re-route my fuel line so it wont fail.

Re: Update

Well that is for the suck. The new one from mopedwarehouse points front, like the stock part.

Not installed yet, but it looks like a quality part.

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