Moons ago I had a MAC go cart racing motor on my mini bike after blowing up many 4 strokes. We would use clay to check head to block clearances when shaving down the head for hi compression. Used model airplane fuel & hi test fuel in a 50/50 mix for more powerat 14 years old. Talk about “boathouse” builds.
Parts were easy as we lived in Phoenix & the Mac factory was 100 miles away in Tucson, Arizona.
Good memoried!!