Just got a Manco Dingo 6.5 Briggs from a friend of mine. Its a project and I knew that going in. So here is where i'm at. The engine needs the pull rope assembly (it was missing when I bought the go kart) it was low on oil (before it was started it was filled to the proper level) and it is smoking pretty bad. The shop where it is currently at wants $150 to order the pull rope assembly and labor for putting that on and checking it out for me. The guy at the shop said it could have internal engine damage that's why it is probably smoking. I don't really want to put $150 in an engine that's not to last very long. So I have been looking at engines online. I have priced some engines around the 5-6 horsepower level but I think I want to go a with a little more horsepower than that like maybe a 9 hp or a little bigger. From what i've been told the Briggs engine should have a 3/4" crankshaft. All the engines I have seen over 9 hp have a bigger crankshaft diameter. If I go with a bigger engine what will I need to change to get it to work properly? Also if anyone can help what engine 9 hp or above would be the easiest to use?