Hi - this is my first time so please treat me gently. I have a three year old Powabyke Salisbury which is working fine, but there is an annoying clicking noise coming from the rear hub. Strangely it only seems to happen when I am sitting on the bike and motoring along. When I spin the wheel when stationary the noise is not there. My fear is there is a problem with the motor. Does it need to be serviced perhap or can I do something myself? Grateful for advice please. Many thanks.