ya sky is right on! these motors are made to run their best around 200 plus deg. and the way that they are made the motor goes through a LOT of stress whaen you start it up cold. espacially the conrod. i heat mine up all the time and my motors all last. its a lot of stress on the conrod when its cold. heck you ever try to turn a motor over w/ your finger when its cold vs when its warm??? there is your answer[X(]