"Clicking" noise, stress problems, overweight
The Roth Motors user manual talks several times about a "clicking noise". They say it is a bad thing and recommend to replace the rear wheel, but they don't explain what the noise is or what is the cause.
As far as I can determine, the "clicking noise" that they refer to are cracked or damaged bearings. Bearings exist in two places: 1) in the wheel hub and 2) in the motor itself.
Generally damaged bearings in the wheel hub will manifest itself when you step on the scooter and apply weight and go forward. The clicking sound will occur if the motor is running or not. Recommended operation: replace wheel hub, or entire wheel.
I have had two instances where the chopper motor bearings become worn or broken. This can also manifest itself as a clicking sound, but at a much higher rate. At scooter speeds this can sound like a humming noise. By rotating the wheel slowly by hand, you can hear if there is noise cause by the bearings. If you remove the wheel and rotate each motor separately it is possible to check which motor is causing the problem. It is also possible to check if the motor axle is loose (another manifestation of motor bearing problems). Recommended operation: replace motor.
The general cause of these problems is overweight conditions on the motorboard. Roth claims that it will handle up to 220pounds. This includes everything including backpack and all other weight in addition to the person riding the scooter. Also hitting a deep bump in the road can increase the stress on the motor dramatically, breaking the bearings.
Using a notched wheel appears to cause problems with bearings (or the reverse, bearing problems can cause a notched wheel).
In addition to cracking or damaging bearings, overweight conditions can cause the two screws which fasten the motor to the motor sled to break or become loose. Check that the motor is firmly attached to the motor sled.