CG250 internals to CG125 cases is a fail

In the end I realised that the crankshaft taper on the CG250 crankshaft is different to the crankshaft taper on the old 6v flywheel crankshaft. The CG250 CDI engine appears to have a longer crankshaft on the flywheel side. I don’t want to machine the crankshaft on the CG250 engine, so that’s it, I’ve given up and re-assembled to CG250 engine to use as is.

CG250 engine project begins in earnest

I bought a 167FMM CG250 (233cc) Chinese copy engine. I’d like to use it in my recently completed silver CG125 but as the old CG125 is 6v with points ignition and the CG250 is 12v with electronic ignition I don’t much fancy changing the wiring harness and all the light bulbs. So I have been investigating swapping the crankshaft and cylinder, piston etc to some spare CG125 crankcases I have. The first issue is the crankcase cylinder opening size isn’t big enough to accept the larger cylinder liner, so today I set about boring the crankcases to accept the bigger liner.

The CG125 is street legal

I had the day off work today. Got my CeeGee through compliance and then decided to further investigate swapping the Chinese CG250 internals into Honda CG125 cases. Got quite a long way in when I discovered the main bearings are different sizes. Gave up and put it back together. I’m so chuffed I bought a small Makita impact wrench. Made the process so much faster and easier, although I did have to get my air one out a couple of times on really tight things. I didn’t know but square number plates are now a thing 👍