The 80 tooth sprocket is mounted on the 16 tooth sprocket of the rear wheel. The 16 tooth sprocket is mounted on the free wheel.
The 16 tooth sprocket is mounted between two nuts: 80 tooth sprocket - nut - 16 tooth sprocket -nut.
The rear wheel is positioned at 1 cm left of the longitudinal axis because otherwise there is not space for the chain and sprocket.
The motor is powerful enough to start from standstill, but I find that a kick start is more comfortable.
For a second build, I would use another sprocket for the motor. Instead of 11 tooth (33km/h) I'd use a 14 tooth (~42km/h).
For the rear wheel I'd use a scooter rim. I'd try http://tncscooters.com/index.php?route=product/product&path=62&product_id=236
with a freewheel assembly: http://tncscooters.com/index.php?route=product/product&path=63_114&product_id=389
I need the hose clamp to tighten the 80 tooth sprocket on the 16 tooth sprocket because the screws don't fit perfectly.