I've set the gap on new points, new spark plug. The airbox is not clogged, but I haven't tried running with it removed. I live in Colorado around 5300ft and I've been meaning to remove the airbox to see if it runs better without it.
Any ideas how this engine will run with the piston installed incorrectly? The piston has a port cut into the bottom of its skirt that can either face the exhaust port or intake port. This piston was out of an old motor and I couldn't see any arrows indicating how it was to be oriented.