hi my yam 250 has totally miss matching frame and engine numbers the frame starts 493 301 9** and the engine number is 434 101 06* would this have been the right engine? if not i need the date of the frame and the date of the engine incase the parts are different i trhink ive got the frame as a 78/79 but thats as far as ive got cheers mick

Mick,

The frame number with 493 would indicate the later models around 78/79 as you say. The 434 engine number is from a TY250A model from 74. The engines are only slightly different with the 434 having the recessed fins on the barrel and the wider engine cases. The 493 engine has full width fins, slightly different porting and the slimmer mag side cases.

Tony

Edited July 23, 200917 yr by tony283

thanks tony that will help when ordering engine parts thank you