SteveT.
100cc
Yes, they are M4.....and the procedure to mount the motor is to remove the shaft collar at the rear of the motor, and then pull the bell off....mount the rear portion of the motor, then hold the collar in place with a pair of needle nose pliers, and slide the bell back on, making sure that the shaft goes through the collar. Then tighten the set screws, making sure that you align the set screw with the flat on the shaft....
SteveT.
SteveT.