Japanese 2 stroke dirt bike engines


Nov 10, 2014
North Alabama, USA
Has anyone here built a motorized bike using one of the under-100cc multi-speed dirt bike engines? I know the single speed Morinis and clones are popular, but the big Japanese motorcycle makers have built lots of small 2 stroke dirt bikes too. Honda MT50 and CR80, Yamaha YZ80, Suzuki RM80, Kawasaki KX65, KX85 and KDX80 come to mind. There may be others as well.

I just bought a used Kawasaki KDX80 engine, and it fits in the frame of my old Diamondback Sorrento mountain bike. Air cooled, kick start, with a manual clutch and 6 speed transmission. I'll probably use a 17" moped rear wheel with drum brake.

Not asking for advice on what I should do to make it safe (brakes, frame material etc.); I'm not a noob. Just wondering if anyone else has built using a similar engine.