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Sealing a black plastic carburetor float


Graham Man
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Ok this question is a little new for me.  There were a ton of large and small engines with these plastic floats.  I have been having problems with my 1980's applications starting to take on fuel, they still float but not the right height.  Hoping someone has solved this problem all ready.  My thought process it you should be able to dip them into some type of epoxy sealant to make them fuel resistant again.  My applications are near impossible to find new floats.

 

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Anything you coat the float with will change it's weight and thus it's buoyancy. Floats that are not brand new will have already absorbed fuel and thus will also be too heavy before coating. If you know the float is heavy, you can bias the setting high to compensate. Unfortunately, this is trial and error.

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NEW plastic floats may be coated with:

 

(1) POR-15

(2) model airplane fabric dope

 

As Joe mentioned, the weight will change slightly, and should be compensated for with the adjustment. It won't be much.

 

I have tried dozens of products, but have found NOTHING that will work on floats which have been in fuel; even if they are allowed to air-dry for months.

 

Jon

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Nitrophyl floats are complete rubbish, and caused a rash of completely preventable carburetor failures in the 80s and 90s. As @joe_padavano said, if the buoyancy is wrong they have absorbed fuel. If it's not too bad maybe you could bias it, but it will continue to absorb fuel and change. Some automakers, GM for sure, wanted you to weigh the float on a scale to see if it was bad. That was pretty much a waste of time, because the nitrophyl floats had a useful life of about 80k miles, but if the carburetor was apart, it had probably already done most or all of 80k. In practice you NEVER put an old one back in unless you wanted to see it come back with a sunk float in a couple of weeks.

 

You can buy blocks of nitrophyl and carve your own if you want, It has been done to replace cork in much older carburetors. Cork must be sealed, and the original sealer (shellac) does not survive in modern fuel. I have heard recommendations lately to seal hand carved Nitrophyl, too, and yes that will probably make it slightly heavier than pure Nitrophyl. Another thing I have heard suggested lately is Balsa. It must be sealed too, but supposedly it starts out more buoyant than Nitrophyl, so maybe you could hit the buoyancy sort of close after you seal it. Of course there is always cork. It must be natural cork though, not the kind that is ground up and bonded together with rubber. That kind of cork is too heavy. Airplane dope and gas tank sealer are a couple of things that might do for sealer for any of those three materials.

 

If it were me, I would find a brass float of about the right shape and solder your arm on. Any replacement you make is probably going to have the wrong buoyancy and need to be set by trial and error.

 

Edited by Bloo (see edit history)
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15 minutes ago, Bloo said:

Nitrophyl floats are complete rubbish

 

How do you REALLY feel? ;) 

 

Unfortunately, I have to agree!

 

Balsa does work; for 25 plus years, we have telling people that were in a hurry (we make rebuilding kits, and put Nitrophyl floats in the kits for carbs that came with cork floats) and just could not wait for us to do a kit.

 

Balsa can often be found in either a hobby shop or a flower shop.

 

Jon

Edited by carbking (see edit history)
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HAHA @carbking you posted while I was typing. As usual, you were right on target. I know it is a bit irrational that I wont use Nitrophyl, considering the dearth of really good solutions, but I classify it like duct tape, automatic transmission sealer, and engine overhaul pellets. :D

 

Edited by Bloo (see edit history)
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