350x-250x-300ex engines - compatible??

[87ATC250R]

Hey all,

I've heard a long told rumour that the these engines are all based on the same cases. Is that true? Are parts interchangeable?

Any insight would be appreciated!

Kris

[hrc200x]

They look very similar, expecially the right case, you can even see the oulines of where the oil cooler should hook in on a 250x/300ex case. The 350x has a oil cooler. I think the 300ex even has a outline for a kick start, but maybe thats cause the 250x has a kick start.

I always wanted to put a 300ex head onto a 350x cyclinder cause the 250x/300ex uses a cam with bearings on it, not sure if everything would line up though. Its funny the 250x/300ex are 4 valves, but only have a single head pipe unlike the 350x.