Re: what did you do to your motorized bicycle today?
OK, you talked me into it.
I already had this spare Mac motor mounted to a plate. The plywood "lever" is bolted to the motor plate at one end and there is a rod (bolt) that slides in the other end. When the rod is under the bike frame's top tube, the drive roller is held up off the tire. With the rod on top of the top tube, the roller is pressed down onto the tire. This worked good for my test, but when I do a real build, I'll figure out a better way to lock the friction drive on and off.
I could have cut the plywood into more of a handle shape but I didn't want to waste wood or time on a quick test. Plus I didn't want it to look like a product from an adult novelty store. I stole that joke from Cannonball2!
It ran really smooth. Since it's locked into place, the motor can't "bounce" at all with road or tire imperfections. Of course, spring-loaded frictions drives don't bounce much when they're designed right, but the springless design has advantages.