Spark plug heat range

[Dragmeistr]

I have a '03 CR250 that I ride casualy in the desert and then take it to the sand dunes and beat on it pretty hard. I was wondering if I should go to a colder plug do to the lugging and revving of the motor? I currently am running a BR8EVX and was thinking of switching to the BR9. Would this also decrease the engine's tendency to knock when it gets hot?

 

[Studboy]

I think that an 8 plug heat range in a stock 250 is pretty generous. I run an 8 in the sand dunes all year long with no problems. I run a 7 heat range plug (hotter) in the woods/trail riding.