Well I have not built a weedeater bike yet....I do have three motors and still gathering parts little by little. Hopefully soon I can get my hands dirty and get it going but have been very busy.
One will be a 31cc friction drive, the second is a 33cc centrifugal clutch with a 2 speed gearbox. The third 31cc motor is just for parts.
The 33cc will be a chain drive using the bicycle existing sprocket (hopefully)
I will have pics up soon.
Check this forum out...DIY Home Built Motorized Bicycle (non kit) - Bicycle Motor at Motorized Bicycle Forum