Newbie 650/ 750 question

[CDHMfabrication]

Hi everybody. This is my first post, I just purchased a couple of motors and two frames to build a pair of bikes for my wife and myself. I used the model ID table under the tech section ( reason I signed up – Very helpful.) So I've now disassembled two of my motors in the last two days. First up was my 78 – 477 model. Everything checks out, motor is in very good condition and ready for cleaning and reassembly. The second motor to be disassembled is model S650-129xxx (forgot my paper with exact number). This motor was seized when purchased. I discovered that this motor has been bored out with a 750 kit. My question is did Yamaha offer a 750cc upgrade from the factory? It seems it has factory rods (stamped with Yamaha 256.) My uncle has had an xs in the past and mentioned as I have read that most parts are interchangeable. My piston pins are vastly different in size as are my connecting rod ends. Does anybody know the specs or differences between the standard 650 and the police version? As this motor was manufactured around the same time as the police versions I was wondering if this could be one of them.

Thanks
Corey

 

[jay760]

The s650 is a early motor while the 447 is late, there are quite a few differences internally between these engines, you can't just swap parts with these, don't get the cams mixed up as these have different gearing on them, although yamaha did do a 750 version they are very rare and there are plenty of 750 kits readily available for the early and later engines.