Some people swear by magical fixes in a can and some people swear at them. The former camp always says "Obviously you did something wrong!" when the gunk gums up everything.
The highest-rated head gasket sealant is rated 4.3 stars on Amazon.
I think that I would want something rated a little better than that to use on an engine.
Old snowblower tires?
Go ahead!
I tried it on Mom's wheelbarrow tire and it didn't do anything, but we already had the can, so we weren't out anything. I bought a new tubeless tire from Home Depot.
It was half off!
I don't think that Harbor Freight had the right size. I went there first.
Fix-a-Flat may work. Maybe not.
I bet that Great Stuff would do the trick, but I need to ask can you make it a solid rubber tire?
Also, it sounds like two-stroke engine, carburetors, and all of that are more trouble than it is worth. Just swap in a Metro engine!