Yes, you want the engine COMPLETELY cool to do the belts. It's for the purpose of adjustment. All the specs or settings are cold. Then, when the motor heats up, the belts get tight...and they do get tight. It's amazing how much these motors expand when warm. I checked mine one time after warm up (cause I had one whining but that's another story) and could not believe how tight they got when the motor's warm. But that's why.