How should I fix this Atc Big Red 200es problem?

While riding my 1984 Honda Big Red 200es, once the engine gets hot it will lose it's spark, and once it cools again, will run. I've checked and changed the spark plug connectors and the wires near the motor but it still has the problem. If someone out there has had this problem and can help that would be great.

I'll check that thanks
Update: I checked with my father (the previous owner) and he said he tried that. Anything else?

Can be the coil when it heats up