working on solving the leaking carburetor problem

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working on solving the leaking carburetor problem

Postby Lurker Carl » Thu Feb 19, 2004 11:27 pm

This issue was discussed at Cubfest and there were some practical ideas thrown about as to the cause and the solution. I've had several non-IH carburetors in the past that leaked fuel past the float needle cage, but once I looked closer at the cage area, the reasons were obvious. The IH carb has rough seats for the gaskets to seal against, so I tried a couple of fixes during the rebuild. They did not work as I'd hoped. There's been a flurry of discussion here about this very problem, so I figured I'd share my experience with y'all.

I stopped by Home Depot this afternoon and picked up a jar of leak detector as per Donny's suggestion. Removed the carb, separated the castings and the gasket was soaked with fuel. So I'm inclined to think the bowl overflowed, pointing fingers at the cage or the needle. I hate that cork gasket, until it dries out it curls and twists around like a road kill snake.

So I rigged up a 'Rube Goldberg' version of George Willer's air connection to find that pesky leak and dribbled the leak detector around the cage gasket. I could only use 1-2 psi, otherwise the float couldn't hold the needle valve closed, but I left it under pressure for about 1 hour.

A tiny little foamy white line formed at the base of the cage on one side. The gasket leaked at the cage, not at the seat. I originally used teflon tape on the threads, so much for that idea. I removed the cage, put a light bead of high performance Permatex Thread Sealant on the threads and reinstalled it for another leak test. After another hour, no sign of leaks.

I noticed the Viton needle valve did not reseat consistantly when I cranked the psi up and down enough to let the needle valve pass air. So, I took Viton needle and cage out and put the original solid metal needle and cage back with Permatex on the threads AND a light bead on each side of the gasket. I retested for another hour with air, no leak. And the metal needle reseated every time I jiggled the psi. I'm keeping the solid needle and cage in so I reset the float height since the Viton needle and cage sit a bit taller in the saddle.

Probably overkill, but I Permatexed the threads and gasket on the fuel nozzle. I also Permatexed both sides of the main jet gasket, but I left the threads alone since they are not part of the leak issue.

Tonite is the acid test. I'm leaving the fuel petcock open and a bucket under the carburetor. I'll report the results in the AM.

Lurker Carl
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Postby Donny M » Fri Feb 20, 2004 12:23 am

Carl,

Sounds like you got her licked. :D :D Another reason for the leak detector...It will find the smaller leaks that soapy water won't.
Can't wait for your post in the morning as my carb parts will be here in the afternoon.
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Postby Lurker Carl » Fri Feb 20, 2004 8:18 am

AM update:

Not quite fixed, it leaked about 1 teaspoon over 9 hours. That's much improved over the 1/4 cup that leaked the night before. Which was unbelievably better than what I started with. Picture Niagra Falls with gasoline.

I didn't check the fuel level after readjusting the float, it was getting a bit late. The float has 3 big globs of solder weighing it down, so I guestimated the correct float height from last week's measurements. I'm going to replace the old needle and cage as well as the float and try it all again in early March.

In the meanwhile, time for some R&R with my lovely wife.
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Postby Rudi » Fri Feb 20, 2004 11:23 am

Carl:

Sounds like you are making progress :!: :)

I shall wait for the revisions until after you get back from that lovely R&R in some place warm :D

Enjoy the vacation with your lovely bride and will look forward to a pic or two!

Cheers
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Postby Bigdog » Fri Feb 20, 2004 4:23 pm

Man! I gotta get out more! When I read Carl's post, I thought Cathy was the R & R! :wink:
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Postby Lurker Carl » Sat Feb 21, 2004 9:45 pm

Actually, she is the R&R. I can't let her know that.
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