Re: How does a clutch work?
There are some good diagrams of how the chinese kit engine clutches work on this site. Motorcycle clutches generally work in a similar way. There is a lever on one side of the engine which has a cam on it. This pushes a rod that goes through the center of the shaft. It would be hard to adapt to a cog on an engine with a solid shaft, but it may be possible to rig something up on a custom made hollow jackshaft.