Motor hub Sprint

[Jeanette Morgan]

I have a Sprint which I'm keeping for spares basically, but I tried my new battery on it and the wiring seems fine, however, the motor kicks in but never quite gets going - it's as if the motor is catching inside somehow. A clue might be that the front wheel will not go backwards very easily, it's as if something is catching, but clearly there is nothing I can see externally that's catching.

How easy is it to open the motor to see if maybe there's something obvious out of kilter inside? As I said it's not the Sprint I am riding, but I was just wondering what you experts think might be causing the wheel to catch (not lock). Interestingly despite revving the bike motor, and it kicking and stopping, when I released the throttle, the battery does not auto cut-out.

Thanks for any replies.

 

[flecc]

The internal freewheel means it's easy to turn the wheel forward with the freewheel action Jeanette. When it's turned backwards it's against the freewheel so the motor has to be turned as well, creating more drag. When you turn it backwards, it will feel notchy as the motor magnets pass the motor poles creating pulses of magnetic attraction.

Therefore that feel doesn't necessarily indicate anything is wrong. It's possible for the gear teeth to get damaged and create much worse drag as the teeth catch and try hard to stop the wheel turning backwards, so that can be the case sometimes.

You can take off the hub end cap after removing the wheel to withdraw the motor innards to see the gear teeth. Here's a photo of the Sprint motor internals showing the three epicyclic gears which act on a toothed rack in the hub shell: