Diffrences between the 81 atc250r and 80 cr250

[Macs]

What is the diffrences between the 2, top end wise? i was told that the stud layout was diffrent but daddio straightened me out on that. then i did a part number search and nothing in the top end has matching part numbers from gaskets to hard parts. i was wandering what the diffrence was between the two. Or if the part number diffrence is cause one is plated and might make a diffrence.

[Saul]

I think it is the 79 cr250, honda had a bunch of left over motors and one the engineers put together a 3 wheeler.

uhhhh what?

[deathman53]

I'm not an expert at it. I know the cr cylinder had a nickel-sil lining and very different porting, as well as a intake and exhaust boost port. The atc cylinder is a steel liner and de-tuned version of the cr cylinder. Just like the 82/83 kx and 84/85 kxt cylinder, de-tuned porting to the kxt model.