Vintage Dirt Bike Q & A

I remember reading that this was possible. what is all required to perform this swap? do i use the CR125 crank or the MR175 Crank?

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Burkemotorcross
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1976 Honda MR175
1983 Honda XL185s
1966 Honda CT90
1994 Kawasaki EX500

I do not think a CR125 will fit an MR175 bottom. The MR175 has long mounting studs that hold the cylinder and the head on and are not mounted in a square pattern. The CR125s cylinders mount with short studs that only hold on the cylinder. Maybe if you removed the long MR175 studs it might work. Anyway you would need the CR125 crank since the MR175 uses a bigger pin for the piston.

No, this swap out does not work. Why bother anyways, just build either or? If you're trying to build a cheater bike you'll be snuffed out immediately, but if for fun then just build the MR175 motor with CR125 like porting and CR 125 gearing.