Actually, I have been thinking of using a normal cent. belt clutch on the engine> going to a driven CVT pulley on a jackshaft, then from that jackshaft back to the rear wheel with another belt.
An idler with a lever could push on the primary belt> changing the ratio on the driven pulley for a higher gear.
My reason for this combo rather than using the normal CVT driver is it is quite wide and I need the space for pulley to drive a generator.
The driven part of the CVT needs to go on a jackshaft regardless of the configuration.