WOW!! Thanks for all the input and advice, Guys. You've sure given me plenty to think about. Sounds as tho even if you don't actually balance a new prop some of you do check it's balance before using it. A balancer is probably next on my list of purchases. I will probably subscribe to the idea that within reason balancing is not required.

High Plains: Could you elaborate on your last comment concerning the "crankshaft counter-balance"? I've searched the forums here but didn't find any detailed information about it. Again, this is my first try at model airplanes, Kadet Mark II and Magnum XLS 46, as yet un-flown. Does this engine have a counter-balance and how would I find it?? Incidentally, since I've been following your advice about checking for the "bump" before starting with the electric starter, I've had no more problems with the prop loosening! Thanks for that.

Frank