Rocket, thanks for info but I'm still in the dark as to frames in general. I'm not sure if any of the numbers mean anything are not. The three frame numbers have all got 175 KTM motors in them, frame # 54 51288074 (Dec 75)is a older frame then frame # 54 40371971 (March 74). Frame # 54 41078661 looks to be a (Oct 74) as you stated but has the 175 motor. Heres a new number, frame number (7 21159825) it also has a 175 motor. D&D