Carb drip - new needle from the good expensive kit won't sea

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Matt Kirsch
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Carb drip - new needle from the good expensive kit won't sea

Postby Matt Kirsch » Mon Sep 28, 2015 3:21 pm

Another point of frustration with my resurrected 1951...

I spent the long buck on the deluxe high-end carburetor rebuild kit with all the jets, gaskets, packings and shafts. Supposedly the "good" kit.

The %$#@ needle won't seal. I've had the carburetor apart 4 times now.

The float height is set properly: 1-13/32" with the needle closed, and 3/16" of travel.
You can hear the float clink up and down when you turn the carburetor over in your hand gently, so it's not stuck.
The float is not taking on gas and sinking, it is dry as a bone inside.

It is a steady slow drip-drip-drip, seems to come out through the bowl gasket.

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Re: Carb drip - new needle from the good expensive kit won't

Postby Eugene » Mon Sep 28, 2015 3:29 pm

Eugene wrote:Bench test for source of the leak:
Eugene wrote:Hose barb to fit carb inlet, clear plastic tubing to match the hose barb, funnel small enough to fit inside the clear plastic tubing and a bottle of rubbing alcohol from the dollar store.

Remove carburetor top, turn and block upside down on bench with hose barb, tubing and funnel attached. Funnel above carburetor, fill with alcohol. Observe needle valve area and remainder of carb top for source of leakage.
I have an excuse. CRS.

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Re: Carb drip - new needle from the good expensive kit won't

Postby indy61 » Mon Sep 28, 2015 3:51 pm

I've had good luck with the Viton tip needle valve and new seat but you may try the old if you think that is the problem.

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Re: Carb drip - new needle from the good expensive kit won't

Postby Don McCombs » Mon Sep 28, 2015 6:24 pm

Eugene's technique may very well show you where the leak originates. If it is leaking where the carb top, gasket and needle cage meet, try a little Permatex High Performance Thread Sealant on the needle cage threads. Sometimes a little corrosion or unevenness on the carb top surfaces will prevent the gasket alone from sealing adequately. Use the sealant sparingly and let it cure at least 48 hours before introducing fuel. Let us know how it goes.
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Re: Carb drip - new needle from the good expensive kit won't

Postby Clip » Mon Sep 28, 2015 9:46 pm

I used Permatex 1 or 2 gasket seal on the threads, but when it came time to put the new Viton tipped needle in, I reused the old all-metal needle. Don't know why, but I reasoned it didn't see much wear over the past 60 years and was still working alright. I used a small amount of polish on the needle and cage and basically lapped them so the mating surfaces were clean and smooth.

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Re: Carb drip - new needle from the good expensive kit won't

Postby Gator809 » Mon Sep 28, 2015 10:48 pm

A trick a old motorcycle mechanic showed me was to put a wooden match in a drill. Put a drop of oil on the seat and then use the match to polish the seat. It's worked every time for me and the only hard part is finding a wooden match
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