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Gotway MCM4 Spark Noise?


TonyS

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I've had my MCM4 for a few months, ridden 571 km, so far and loving it. However, I'm concerned about it's health.

Recently it started making a strong 'crack' noise that sounds like an electric spark. It sometimes doesn't do it at all, but other times after riding 10 minutes or so, the 'cracks' start. Initially they occur when I go over a bump, then gradually happen more frequently until they're every few seconds.
 
I've opened to case, but can't see any evidence of arcing (burned insulation, etc.).
 
Has anyone heard of this before? Any ideas would be appreciated.
 
Here's short video I took at night to see if I could see a flash, but no. You can hear the 'cracks' from about 25 seconds in.
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Here's some more information on this. The problem is still not fixed, so I'm still looking for advice. However, this may be interesting.

I opened the case and looked for evidence of arcing/sparking and found one of the motor power wires had an exposed conductor.

https://drive.google.com/open?id=1VZenp5LWQO8bskDij-P5wZvPmLv7-4rn

This looks like mechanical damage more than a break down of insulation, though. I could see no evidence of burning or arcing on the exposed wire or any of the adjacent wires. I suspect this was caused during manufacture when the sheath of the motor cable was stripped back to give access to the wires inside.

Here is my repair (overkill with heatshrink!).

https://drive.google.com/open?id=1NZKvas0hV34y4bHn6bc6yio2rKiL1nmz

On a test ride I started hearing the same noise after about 5 min. At first the 'cracks' happen when I ride over a sudden dip (e.g. from a driveway to the road), but they occur more frequently the more I ride. It seems to me that the arcing (if it is that) is occurring inside the motor.

Opening the motor is a much bigger mission. I'd appreciate any suggestions about the 'crack' noises or opening the motor.

 

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Welcome @TonyS

Did you check if the pedals/pedal hangers/ axle are ok?

There were also (seldom) reports of forgotten washers/screws inside the casing, hall sensors getting loose inside the motor.

Hope there is an easy solution for your prob! I could not identify something from your video, beside this "matallic clank" sound...

Is it somehow regular? Once a tire rotation or something like this? Or "totally" random?

Some had "just" the air vent of the tire scraping once the casing is shifted by the riders weight - i know this should make another sound, but just as idea.

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1 hour ago, Chriull said:

Welcome @TonyS

Did you check if the pedals/pedal hangers/ axle are ok?

There were also (seldom) reports of forgotten washers/screws inside the casing, hall sensors getting loose inside the motor.

Hope there is an easy solution for your prob! I could not identify something from your video, beside this "matallic clank" sound...

Is it somehow regular? Once a tire rotation or something like this? Or "totally" random?

Some had "just" the air vent of the tire scraping once the casing is shifted by the riders weight - i know this should make another sound, but just as idea.

Thanks for your ideas. I'll check the pedals tomorrow, but I haven't noticed anything unusual about them.

The sound is not regular. After riding for 10 minutes or so, it occurs at intervals of 3 - 10 seconds, so I don't think it's related to the wheel. However, I'll give it another test ride tomorrow and experiment with my weight.

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@TonyS Same to me, after ride a while, sound comes again. Not regular occur, so your situation is very similar to mine. When I open the shell, I even couldn't find any  scratches on shell or pedal. If you have the same situation, check your motor bearings.

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