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I've never had an issue with my chain falling off until today. I put my bike in the bike holder in front of the drivers window. Perhaps something got knocked or moved?

I could have a dirty cassette or old chain but it seems strange to go from zero issues to not being able to keep chain on.

My chain falls off only when I stop pedaling... When I look down at the crank, when I stop pedaling, it spins faster and faster until the chain falls off. Ideas?

I have an e bike with bottom bracket motor bafang bbs02.

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  • Where does it fall off? Do you have one chainring or several? Do you have a derailleur? If you lift the bike off the ground and turn the cranks by hand, does the chain come off ?
    – Criggie
    Nov 30, 2023 at 1:11

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If the pedals keep moving when your feet are completely clear, then they're being pushed/pulled by the chain, which is being driven by a jammed up freehub inside the rear cassette. The sound of coasting may have changed. A good deep clean may be enough to fix this for now.

If the motor is doing the driving, then something's damaged on the electric side and the motor is activating when you don't call for power. Eliminate that by riding around without the battery connected and see what happens.

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