differences from the late model 125m to a 200s engine

[airbats801]

I picked up a blown up parts 125m 1986 or 87 model. Whichever the later style upright started. I'm curious what parts off the top end interchange and what are the differences in crank rod and piston size.

I'm pretty sure the heads are 100% interchangeable, but I'm unaware of the rest. Can I toss on a jug off a 200 or 185?

[Howdy]

The jugs are different. The 125 has a cam chain tensioner mount, the 185-200 doesn't.
The heads will swap, but the cams don't with out modifications ( 185-200 cam in the 125 ).
A good 185-200 head with a modified 200x cam on a 125 will wake it up.

The 125 cams are shorter due to No CDI on the end like the 185-200 has.
Howdy

[YTZ drew]

I can tell you that the jug is the same height as the 185/200 jug. All the CB/CL/SL 100's and 125's use a shorter jug. I thought about putting an atc125 jug onto an extra xl185 bottom end I had around, and boring up to a CB125 piston, would make for 134cc with the longer stroke of the 185 crank. Never got to it though.

Oh, and the rear crankcase mounts of the ATC/TRX125 are wider than 100/125/185/200 engines, due to the reverse and electric start. They wont fit into any other frames.