ORIGINAL: Konrad
The K&B engine is of little relevance to the Fox. Most of my Foxes use a head shim. They are often an aluminum, so there is always a metal to metal contact in the head sealing area. If you don't have piston the head contact the head gasket or lack there of shouldn't be an issue. It isn't an issue as far as fuel draw.
You should be able to get the engine to ''run'' if the crankcase is properly sealed. Power, over heating and throttle response are all issue we can work on after you get the engine to run.
The only reason I mentioned the K&B is in reference to starting in reverse. I know its common, but the fox doesnt want to "right" itself as well as my K&B did. That aside, I have a hard time getting it to "run". The Backplate is sealed, and the carb is sealed. The only thing that isn't totally sealed is the head. The piston does not hit the head, obviously. Since the weather is shaping up, I'll try running it again this afternoon. With a little luck, it will start and run in the proper direction long enough to get it running good and proper. I'll post back with my findings.