Santacruz,

You say its cold? Thats when they will over heat the easiest. When its cold it will run alot leaner and will heat up quicker. You HAVE to watch your temps no matter what. Thats the number 1 rule with nitro rc. Temps change every day so tuning will very from day to day. If you dont watch your temps and you have over heated the motor more than a few times it may be worn out already hence the word SHOT! . Sounds like you are overheating the motor and it wont start till it cools down. You have to watch temps period!