The motor doesn't have a problem it need to be retrofitted to run in a mini bike / go kart. Only reason I have one is everyone says there cheep then I got one then it needed a con rod , flywheel, valve springs, spark plug, header, 22mm Mikuni, manifold, air cleaner, hardware, what else? It all adds up. Wish I would of put the money in to a Briggs not a foreign motor. I actually feel bad about it like I let down America.
The thing about the pred is they are cheap if you run them stock out of the box, maybe throw on an air filter and exhaust for a little extra, and they really work quite well that way on any minibike that you want to cruise around the neighborhood with. Once you start opening them up and building race motors it is going to get more expensive just like anything else. Speed costs money, simple
I used the zip ties on as someone noted here on the forum and it stopped the surging - goes really fast. But doesn't the zip ties really defeat the purpose of the governor ? I cant see spending hundreds of dollars to change internal components and rather buy a B&S like my old Mini bike I had as a kid had - don't remember a surging problem on it ? 3.5 hp enough ?