August 6, 20205 yr I hope there is someone in here with insight into engine issues. The thing is, my wife's MBK electric bike with Yamaha mid mount motor behaves somewhat worryingly. It runs really well for the first few miles. Suddenly, loud periodic noises begin to come from the engine and it loses traction. The noises may be short-lived and sometimes longer-lasting, but they are recurring once the bike has been riding for a while. My immediate diagnosis is that the gears somehow do not sync - a bit like when the gears in the car gearbox do not just fall into place if you do not get the gear lever fully in position (not that it has ever happened to me : D) It does not sound like it has anything to do with worn ball bearings, but that it has to do with the actual mechanical transfer between the gears. It is long overdue on the other side of the warranty, so there is no help to get there. I am in all modesty quite handy with fingers and would like to take up the challenge of disassembling the engine, but it would be nice to know a little about what to look for. Immediately, of course, I hope that it is something as banal as missing or stiff grease that just needs to be replaced so that the parts can slide properly, but fear that it is about worn gears. On the other hand: I suppose that it would be possible to find new wearing parts at an affordable price on eBay or elsewhere? Good advice on where to buy this kind is much appreciated) Bertil
August 6, 20205 yr I think more likely it's an electrical sync problem, like the hall sensor connection or a phase wire connection .
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