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Thu Feb 20, 2025 11:54 am

this is the third carburetor developing a slow leak at the bolt on the bottom of the bowl (access to main jet). Anyone have any thoughts on a fix? I have an aluminum washer on it - is that part of the problem?

Thu Feb 20, 2025 12:52 pm

Zylinderkopf wrote: this is the third carburetor developing a slow leak at the bolt on the bottom of the bowl (access to main jet). Anyone have any thoughts on a fix? I have an aluminum washer on it - is that part of the problem?

Should be a red fiber washer/gasket.

Thu Feb 20, 2025 2:47 pm

Remove the float bowl plug, clean and dry all mating surfaces, then apply some gasket sealant to both sides of the float bowl plug seal and reinstall. Permatex aviation, high tack, super 300, or even gasket shellac compound will all do the trick -- don't use RTV.

Thu Feb 20, 2025 5:04 pm

mukluk wrote: Remove the float bowl plug, clean and dry all mating surfaces, then apply some gasket sealant to both sides of the float bowl plug seal and reinstall. Permatex aviation, high tack, super 300, or even gasket shellac compound will all do the trick -- don't use RTV.
RTV is not gasoline resistant. If you don't have the "correct" sealing washer, I wonder if a copper crush washer would work.

Thu Feb 20, 2025 5:56 pm

Our local hardware store stocks red fiber washers back in the nuts and bolt drawer section somewhere....

Thu Feb 20, 2025 9:01 pm

I dont think the aluminum washer is correct here. it wont be soft enough to seal given how little force you can apply on the bolt without stripping the threads. fiber washer can be used here. The carb body is just to delicate to allow high enough torque on that bolt to assure sealing with an aluminum washer.

use of sealer is risky, as sealer residues may get into the carb, into the fuel, and then clog the jets. Use a fiber washer for trouble free service.

Thu Feb 20, 2025 10:39 pm

zerotofifty wrote: use of sealer is risky, as sealer residues may get into the carb, into the fuel, and then clog the jets.
Not in the least bit risky, provided you're not foolish enough to slather sealant all over the plug and its threads. :roll:

Thu Feb 20, 2025 10:43 pm

Fiber gaskets is your best bet. Originals have lasted 40+ years. With no leakage. Or sealant.

Fri Feb 21, 2025 7:34 am

Most the carburetor repair kits come with the fiber washer, there's an example here:
https://www.thesamba.com/vw/classifieds/detail.php?id=2699178

Fri Feb 21, 2025 7:39 am

Since no one has said it yet, I think an aluminum washer would be 1-use only?

It would crush to fit and then as soon as the bolt moves for any reason, it could start leaking.

Fri Feb 21, 2025 8:39 am

thank you everyone for your responses and advice. I will try cleaning up the mating surfaces and using a fiber washer instead of the aluminum washer. If the leak persists I will try some permatex aviation.

I will report back.

Fri Feb 21, 2025 9:00 am

note a solid aluminum washer is not a crush washer. a true crush washer has a hallow core, and they are indeed designed to be one use, but can on occasion be reused in a pinch. for this application a fiber washer is correct. do to the soft carb body, one may risk stripping the carb threads when attempting to crush a solid aluminum washer, unless it is extremely soft aluminum.

Fri Feb 21, 2025 11:18 am

Not all carb rebuild kits come with a fiber washer for the float bowl plug/main jet holder. Some come with copper, some come with aluminum.

Yes, the aluminum washers are meant to be single use, same as you'd expect for any metal sealing washer. Yes, they are a supposed to be a soft aluminum meant for such purpose, but IMO they do tend to be a little too hard. The same problem exists with many of the cheaper oil change gasket kits these days.

In my opinion and experience, using a little sealant on the washer before install helps to prevent any possible leakage due to hardness or minor deformation issues. It also allows one to reuse either the copper or aluminum washers several times which comes in handy if you don't have a stock of spare rebuild kits or a reliable parts source within a reasonable distance. Regarding the fiber washers, they tend to wick fuel over time if left untreated prior to install -- like most other paper/fiber gaskets, they benefit from a coating of gasket shellac before use.

Yes, the carb body is made out of a soft alloy, but then again the bowl plug/main jet holder often is a softer metal as well. Yes, if you're a gorilla about tightening things you can strip the threads out easily. Use a little sealant on the washer and you won't have to tighten it so much.