Marine Engine Clutch?


New Member
Dec 6, 2008
Hi guys,
I just bought a 50cc 2 stroke off of eBay for a fiver, and always wanted to mount an engine on a bike.

Apparently it hadn't been run in about 2 years, so after a little clean, and some fresh fuel, she fired first time. Its pretty light for an engine of it's size, and I've looked at various options for driving the bike..

Its a pre-war fold-away thing, and i thought I'd give it the light of day, after i found it abandoned in a hedge at the back of our garden.

I tried to build a friction drive, but it didn't prove to be the best option, i couldn't get it to work. I spoke to a mate, who gave me his old go-kart clutch, in need of springs. However; the clutch is for a 3/4 inch shaft, and the 2 stroke I've got has a 18mm thickness (I think), but it's tapered. So from 18 to like 8mm..

I was thinking of buying the clutch from a pocketbike (im not allowed to post the link)

clutch, and then the drum too, and use that; unless you guys can think of anything else?

I had another idea of removing the taper with a lathe, and then building a shaft extender, to fit the standard clutches from karts...
But i dont know if the clutch would be too heavy for the engine (cut in rpm's); she's only a 1.7hp. I dont know how its so small from a 50?

And then gearing..
Its just getting more of a problem tbh. But i think sorting the drive would be a start.

The only advantage that the engine has is that it's metric, and not imperial, like the Triumph Tiger Cub thats sitting in the garage ;)

Oh, and money is a bit of an issue, im only 16, and sitting A Levels just now..

Cheers for any help you guys can do,
Last edited:

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
up north now
Well it sounds like you have some good ideas to get you started....
50cc is more than enough to move you right along. Have you considered using a jackshaft roller set up like deacon used on his electric bike? It's easy on the shaft and can be made for a few bucks. Look under deacons thread about electric bikes here in the DIY forum.