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Discussion Starter · #1 ·
Hey all,

So I went to ride my bike this morning and I turned the petcock onto the 'on' position and started it up. I let it idle while I was getting my helmet and jacket on. When I turned back to the bike there was a large fuel puddle underneath it. I traced the fuel to a hose that is coming out of one (or both?) of the carbs. Turning the petcock to the off position seems to resolve the leak, but doesn't help much when it comes to riding... :?

Any ideas on where to start?

Thanks,
Matt
 

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Floats are sticking and/or a bit of trash in the needle valve.

Quick fix is to gently tap the bowls with a wooden dowel or hammer handle. This usually frees up a sticky float. Especially if the bike has run leak free before...

Otherwise, remove bowls and check float operation and clean as necessary.

Kirk
 

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On the set of 1972 carburetors I just bought from a guy he said the bike ran fine, but leaked gas out of the overflow hoses like that. It's either the needle not seating right or the floats. In my case, the floats are fine, but I noticed there is zero spring tension left in the needles (the little spring in the bottoms of them). The needle seats sometimes get cruddy but I also think these springs need to be in good shape in order for the seal to be made properly.

So pull the carbs, pull the floats off, and check out the needles themselves. Then while you're in there, take a q-tip and put a little dab of toothpaste on it and use a drill to spin the q-tip at high speed up inside the needle seat.

The toothpaste is a very mild abrasive, like valve grinding compound lite. And it'll clean the tarnish off of your needle seat and make a better seal.

Only do that if tapping the float bowl doesn't fix the problem. Most of my older bikes leak gasoline if I don't turn the petcock to the off position. All for the same reason, bad needle seating action. I've been too lazy to fix it and am just in the habit of turning the petcocks off on all of them each time I park them. If they're leaking gas while running though, it's more important to seal up that leak.
 

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AHHHHHhhhhh! I forgot about the "toothpaste" technique for polishing! thanks for the old tried and true reminder :)
danWI
 

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Discussion Starter · #6 ·
Issue resolved.

I wish I could tell you guys what actually fixed it, but after tearing open the offending carburetor and not seeing anything glaringly wrong, I just QTipped it and put it back together. Problem solved?
 

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Q tipped it?
 

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Plus, now it has that EXTRA whiteness and minty-fresh! :mrgreen:




I'd never heard of using toothpaste, but I HAVE used garden-variety liquid chrome polish on a Q-tip. It works great to really shine up the brass up in there. I think it was Ray (fasterspider) that first gave me that hint.
 

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For me the tip that helped was to use a drill so that there's enough speed/friction to heat up the q-tip. This is the only way I've found that will seat a Dellorto carb needle in my Vespas to overcome the gravity of a full tank of gas when you forget to turn off the petcock.
 
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