Sounds like a problem I had with a Go-Tech 26 engine. The pinch was so tight the engine overheated horribly and it never did break in.........it broke! It was soooo rich it would coat my finger with oil so it dripped and left a snail trail when driving around. It finally blew up! If you tried to run it hard at all even after 1/2 gallon of fuel it would just pop plugs left and right! I got another one just like it, took it apart and ran a brake hone through it a couple times. That cured the overheating problem and I am still running it on the same break in plug with no problems! I did some other mods to it as mentioned in my "Doubled my fuel economy" thread.