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If this happened suddenly, then it maybe the crankshaft gear circlip has snapped. This is quite common and allows the crankshaft gear to rub the transfer gear cradle or one of the transfer gears, depending. This gives a high pitched whirring sound that can alter with pedal/motor load. Have you...

The clutch bearing runs on this shiny bit and over greasing can reduce the effectiveness causing it to slip.

It sounds like more of a whine than a deeper grumble? Personally, I would say it sounds gear related, but gear noise/failure is very unusual? I normally only see it when the motor is full of dirt or something has broken, but your motor does not sound loud enough for something to be physically...

I have yet to see a Bosch run out of grease yet. Sounds like warranty time to me. If you get no joy, just send it to us at Performance Line Bearings we will soon have it running like new again 👍

Yes, this motor is the early Yamaha motor with square crank drives and is different internally and supports the ISIS crank drive.

This is an issue we hear a lot of people ask about. We have repaired several motors with this issue and managed to get rid of it. I am working on a modification that should help ensure the noise never returns.

We currently service/overhaul Brose, Bosch, Yamaha, Impulse and Panasonic motors, although some Brose repairs are currently limited, due to the way they are built. We have released a video of a Brose overhaul if your interested As for reliability Bosch Vs Brose, they both have their issues...

All Bosch motors will whine very slightly when in low gears at slow speed, this is normal and tends to disappear as speed picks up. I have ridden a lot of ebikes with all different motors, but never noticed a rough feeling through the pedals, unless the bearings, pedals, chain etc. are shot...

It sounds to me like the crankshaft gear retaining circlip may have broken? This will give popping crunching noises if any bits go through the gears and intermittent noise as the gear moves back and forth on the shaft and starts wearing away at other motor parts. Do you ever feel any rough...

Many people asked, so we have delivered, and what a specimen we found to overhaul! :eek:

I have seen the insides of hundreds of Bosch motors now. Ranging from 150 miles to 15,000 miles. It would seem that any mechanical failure up to 10 to 12 thousand miles are water related. After speaking with the owners there has generally been a reason for that (dropping the bike in the river...

No, sadly I can't get hold of them at all.

Hi Tompat, I believe the MudStop does work a lot better than the Bosch "seal". When I remove the gears to change the main motor bearing, you can see where the dirt and grit has come through the outer ring of the Bosch seal. I believe that because it is set within the motor cover, dirt sticks to...

Just a bit of news, we have now added Bosch motors and MudStop bearing protectors to the site shop. You can now buy a motor outright, we do not expect one back in exchange. If you are a hire company, shop or just want a back-up motor for customers or yourself? They are now available here...

The big debate over which motor is best / worst etc. will, I guess, rage on for ever. But, just for those who believe one motor is better than the others, here's what I have repaired in the last 8 days... Bosch 2 Yamaha 4 Brose 2 Impulse 1 I don't currently do Shimano, although I am asked...

:D:D:D I see these same arguments on all the forums I visit, all over the world! Take it from me, each motor has its good points and bad points. Just know that nearly all the motors I repair have normally been damaged or destroyed by their owners. They have not failed through any fault of their...

It could always be a worn sprocket or chain? If it's a Haibike, look at the SES sprocket?

No, grumbling noise either way is bad. When you turn the pedals forward you are spinning the main motor bearing, idler bearing and crank bearings, so if there is noise it's likely to be one of them. Turning the pedals backwards, you are only turning the crankshaft bearings, so if there is noise...

Intermittent vibration is usually caused by the small idler gear bearing starting to fail. If this is the case then your main motor bearing should be in poor condition too? Remove your chain from the front sprocket and turn the pedals forward, listen for a grumbling noise, this will most likely...

At Performance Line Bearings, I have now stripped and overhauled a considerable number of mid drive motors of all makes and models. And I have now seen the internals of enough Bosch motors to build a fair idea of what lasts, doesn't last and why the failures occur. 95% fail due to water ingress...