Strnage issue

[Spermy]

Took my son's pw out the other day and it was running fine. after about 45 minutes it would not idle. I could start it with full throttle, but the bike would never get up in the "power band". let it sit for an hour or so while we rode other bikes. wen to load up and it was running fine. I didn't notice an overheating issue. Could the cluch have just been hot? Everything engaged fine the engine just wouldn't top out and it would die if you didn't stay on the gas.

Thanks.