Vintage Dirt Bike Q & A

MR175 Cylinder on a MT125???
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Author:  swatdoc [ Thu Dec 29, 2022 11:54 pm ]
Post subject:  MR175 Cylinder on a MT125???

Hey guys I'm looking to pick up a Honda MT125. The plan is to keep it passably street legal but trick it out with some CR goodies and a full red paint job. I'd like to get as much power out of the motor as possible. Would a MR175 cylinder bolt on by any chance. Even if I had to have the cases machined that would be OK.
If thats not a possibility, what are suggestions for beefing up the stock motor? I have several CR125 motors, but need to at least keep the MT center cases, so the motor numbers will match for registration purposes.


Author:  m@tt [ Fri Nov 03, 2023 3:47 pm ]
Post subject:  Re: MR175 Cylinder on a MT125???

The MR cylinder will bolt up , but the cases will need machining to take the larger sleeve . It will fit straight onto the 76-78 CR cases so if you have those , you can use for measurements.
The snag is you need the MR crank / rod , which is the same stroke as the 125 , but longer and with larger bearings due to the heftier piston
Might be easier to use a CR top end and ignition (if you don’t need lights) the CR 6speed will also fit in the cases

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