Thanks for your interest and compliments.
The cush drive softens the drive train and gives a spring feel when shifting. Before installing it, there was a clunk and a shock load to the hub when the clutch engaged (centrifical clutch). Now it is smooth shifting, and you can hear the spring in the sound of the motor when the clutch catches. I think it will make the shift hub last longer.
The hardest part about motorizing this bike is that the rear hub is extra wide. I scoured the internet looking for a wide shifting hub, like something from a pedicab or tandem. I didn't find anything for a reasonable price, so I put the spacers inside the chain stays to accomodate a standard width hub. Then the problem is to get the chain around the wide tire to the narrow hub, so I incorporated the little Jack shaft with the spacers on the right side. This gives it 4 chains, instead of the usual 3 for a bike with a shift kit.
When I started this build, I was trying to save the original paint job, so everything is bolted on, but then the frame cracked (where the primer is in the pics is where it cracked). I brazed in an angle bracket to fix it. Now that the paint is messed up, I will probably braze everything on. I plan to make a weldment for the engine base to include the attachments for the idlers, Jack shaft, cush drive, and a shifting hub, then this weldment will be brazed into the frame on saddles.
I think the shift hub would be better under the motor base, rather than in the rear wheel. This way, it will spin a little faster with less torque.
Before doing those mods, I'm planning to build a trike. There is a nice Schwinn trike, new for about $250, then for the engine, I like the Honda 4 strokes with tranny, such as used on pit bikes, and kid's ATVs. I think there is a 49cc model that would be legal here in California. Also I saw a big bore kit for it, stamped 49cc.
Here are some more pics, I invite your coments.