My 2010 Wisper 705se has been my main form of transport for 5 years now. Recently, my local bike repairman (very competent and friendly but not an e-bike specialist) told me that the rear gear cogset needed replacing; but that he couldn't figure out how to remove it from the hub motor. The local e-bike specialist has unfortunately stopped servicing Wispers, and I can't find any information on this online. So: can the cogset be removed from the motor? Or would we have to replace the motor to replace the cogset?