Chinese engine used as friction drive?

[boyntonstu]

Has anyone done this successfully?

 

[wheelbender6]

A friction motor should have no gear reduction. A roller around 1" diameter should be mounted directly to the engine crank shaft to provide the proper gear ratio. 2 stroke China girl motors have a built-in 4:1 gear reduction. Using cave man math, you would need a 4 inch drive roller with the 2 stroke China girl to have the same top speed.
That is the main reason that you see goped style engines on friction drive bikes instead of China girl engines.

 

[boyntonstu]

A friction motor should have no gear reduction. A roller around 1" diameter should be mounted directly to the engine crank shaft to provide the proper gear ratio. 2 stroke China girl motors have a built-in 4:1 gear reduction. Using cave man math, you would need a 4 inch drive roller with the 2 stroke China girl to have the same top speed.
That is the main reason that you see goped style engines on friction drive bikes instead of China girl engines.

Thanks,

Is it difficult to eliminate the 4:1 reduction?

BTW A 4" roller is not too difficult to imagine.

 

[wheelbender6]

You can remove the drive sprocket and push the cross shaft out the clutch side. Then you would need to attach a drive roller to your engine crankset.
Friction drive kits (like Staton-Inc, ThatsDax) will bolt right up to a Honda GX31, Tanaka, Subaru and many other engines.
Modding a China girl for friction drive is a lot of work and probably saves no money in the long run.