I have an old (20+years) engine on a Sears craftsman snowthrower, that I want to use for a go kart. I cannot identify the engine. The sears www3 site gives me a diagram, but no manufacture name. The diagram matches the engine I have. Sears part # 143604012 (4 cycle engine). On the engine is a tag with that number, but how do I find the manufacturer? I want to do fixes to it before I mount it, but sears doesn't offer parts support for such an old beast.

it might be a tecumseh, try looking around on the shroud for other numbers, they usually get painted and can't be seen easy, or get a little rust around them. if its model, type, and code.....well its a briggs.

The 143 does say it's a Tecumseh engine.
Go to Sears Parts online at http://www3.sears.com/
Enter the model number as 143.604012 They still list ans sell the parts.