Soldering an aluminum carburetor

Is there any recommended flux?

Does it "wick" into a crack?

Is it likely that I will melt the carburetor
while I'm trying to repair it?

If I use it on the block, will it melt when the
engine gets hot?

Any suggestions, Thanks, Mike

I would not put into question the solidus and liquidus temperature of that type of material in this application. I really doubt the low temp solder in the 400�F range would be an issue but possibly under certain conditions it may come close to it's melting point.

We have several special application solders/pastes and some are only in the 300�F range. That's close to the melting point of polymers and resins.

The carb is a zinc die casting which will have a melting point close the same as the #328. Here's what I do with zinc die castings when using #328.

I use a container of slightly wetted sand to press the part into. This makes a fairly good mold if the part sags and usually allows it to cool off in the same shape I started out with. You can also use a low temp solder with bond temps in the 400�F range if the crack is in an area where the sand mold is not practical. I haven't taken the temperature readings on a small engine to check operating temps but I can do that for you with my non-contact pyrometer if it helps you out. Someone else probably knows if operating temps would exceed 400�F or not.

I was pretty surprised by the price of those small engine carbs once. You may be able to find a carb body at the local junk yard. You can get a carb rebuild kit for not much money. I bought one for $8.00 this summer for the briggs on my Troy built.