No power, hard start, 5hp go-cart

I'm trying to fix an old go-cart with a Tecumseh 5hp model OHH50 engine for a kid for as little money as possible. He's only 10 and his mother is going through a divorce and has little money so I told him I'd look at it and see what I could do (to cheer him up a little in these hard times he's going through). So any $ will come from me. I'm very experienced with car engines.

It's very hard to start and when it does it has almost no power and runs eratic. It has a compression of only 30psi so I know that's the problem. Before I put some oil in to test for bad rings I thought I'd ask here for any suggestions. I could afford rings but if it needs over boring or valve work that's another story. Any suggestions on what to do if it does or how to tell? Is it possible for me to do valve work? It doesn't have to be perfect but it will need the compression to be better. I saw elsewhere on here 70psi is about the minimum for small engines - does anyone know the spec for this engine? Also, does anyone know what the valve clearance should be?
Thank you.

 

I once worked for an engine rebuild shop and the owner said he never machined valve seats, he would just lap the hell out of them.