Js400 440 550 parts interchange?

[Matthew Daniels]

I'm bout to be fixing up a 1976 js400 and I can't find anything on the internet about what parts will interchange mostly in the motor and it may need a crank so I don't know if there the same as a 440 or if there shorter stroke the motor looks the same as 440 and 550 also wondering if they are the same will a 550 cylinder and pistons bolt on

 

[Mike W]

A 550 cylinder will bolt up to 440 cases. Not sure about 400 cases. 400s had a full circle crank that isn’t compatible with your later 440/550 cases.

 

[Meeker]

Keep the 400 motor as is. Buy another 550 motor and electrical and drop that in.