You may have a problem with your front crankcase bearing located near the carb. If its binding or failing it will cause the carb to become too hot and the feul will boil before it gets into the crankcase. An egine with this problem may start up well cold and have its needles set correctly but but as the bearing overheats it causes the mixture to lean out as the feul starts to boil before it gets through the carb.

When re-starting hot, remove the air filter and look to see if the feul is bubbling as it enters the carb.

Dont ask me how I know about this.