79 yz400 motor is it the same as a 77

[Paul552]

Will a 79 yz400 motor fit in a 77 frame?? Sure someone here will know.
Also are there any differences? In the 2 motors

Thanks in advance

[Viper666]

Completely different.
The 77 & 78 are the same the 79 was unique. It uses the same shaped cases as the 78/79 250 but the crank, cyclinder & pistons are a one off. The IT425 uses the same crank. YZ then went to 465. Different cases again.

Some parts are interchangeable but not many.

That said you should be able to make it fit relatively easily but why would you? The 77/78 400 were just as good. (For most riders)

[Paul552]

Sweet thanks. All that said it would bolt in?

[crossedup2]

Yes because the frame rails at the bottom are longer on the older 400 frame

And

No, not without a lot of welding and frame mounting point changes. Eg the front bolt holes and plates are different.

I'll  swap you a yz250E frame for a 77 frame.
All 77 plastics swap over as they are generally the same.
regards
Peter B