I have a Honda GX160 on a gokart. I'm experiencing a problem, I think it is an air leak. The engine runs on the choke, but once you let the choke off, it sometimes idles slow and sometime high, it doesn't rev up very well and stalls very easily. I've put rtv on the plastic carb insulator and the gaskets which seems to have improved it a little bit but not much. It has a brand new carb as well. I'm thinking it might be a cracked head but before I take it all apart, is there any other causes of this?