2004 Foreman not running right after rebuild

Please save my marriage! I had my cylinder bored .20 over with new piston and rings and also had new valves installed by local Honda dealer. I was running the ATV 1/2 throttle in the field after ring break in and it just lost power, but yet idles. When I let it cool off it started right up again until it got hot and shut back down. Checked carb several times which is to me not the issue. Fuel flows easy when draining tank back into can. I did adjust the valves to .006 when the motor was still on the bench, so I am confident it is correct. I will be checking the coil next but do not believe it would go out at the same time as my rebuild. This thing ran flawless until my rebuild. I went through 1388 posts on this forum and found others with similar problems, but nobody comes back and posts what their solution was.