Cannondale trail 4 bafang ebike

Description:

Cannondale trail 4 with 29" wheels and cable lock front forks. Thumb throttle Fitted with a bafang 750w motor( motor is quiet and smooth). Display is. Varstorm. 29" wheel and I say the frames a large. Does about 35-40mph
Bike does run great but however after a short distance showing err21 speed sensor. Could be an easy fix for someone if they know what there doing and the knowledge as I haven't got clue and tbh lost interest and gone back using my Carrera peddle bike.
Comes with charger that automatically turns off once fully charge. The lock has been removed on the battery by previous owner however I think the battery can still be removed if needed £400
Collection Sutton in ashfield any questions please ask and I tried and answer the best I can but with ebikes am very limited in knowledge