I'm interested in this as the owner of a 600 mile BBS01. It is completely silent so far, I really have to struggle to hear any sound from the motor. I suspect that the UK seller may have repacked it with grease before i got it. To be fair, the idea of having to tear down a small motor bike engine at around 2500 miles probably went out by the 1930s, and certainly none of my motorbikes have needed any attention beyond the oil change maintenance expected of high speed petrol engines, but they are hammering around much much faster than these wee electric ones, and putting out far more power. They do have bearings speced for the job mind you and are very well lubricated. My 17000 odd miles, twenty two year old CG125, sounds like a new engine, as does my cb250 with 14000 miles, but they have pretty massive bearings and high pressure lubrication. At 11hp and 20 Hp they are working vasty harder though than these ebike motors and typically have crank shafts rotating at 100 revs a second. These small commuter bikes well looked after regarding engine oil maintenance are known to run to 75000 miles.