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smaking sound on the motor

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    smaking sound on the motor

    I have a new mid drive 1000W bafang motor and when on the throttle while in the lowest gear on the cassette (smallest ring) I continually hear a loud sound from the motor like something is smacking it. If I shift into one of the higher gears it doesn't happen, but the bike doesn't go as fast when in the higher gears. I'm thinking the chain might be too long (too much slack) and its getting chain suck into the motor? Should the chain be shortened a link or two? any advice.

    Thanks,

    #2
    I think you mean the highest gear

    Sounds like the chain is skating (slipping across the teeth) on your highest gear - this isn't uncommon especially if you've been running moderate to high power at low pedal speeds in the high gear which puts a *lot* of force on the driveline - it's very difficult to see any visible damage to a cog that skates so don't be surprised if it looks ok and you are getting the skating

    How much has your chain stretched?

    If it's a cassette (vs. a freewheel) you can generally replace just the high gear cog but either way, cassettes and freewheels aren't terribly expensive however if you have significant chain stretch likely ought to just replace the driveline (chain, chain ring and cassette)

    With a mid-drive you should keep the pedal cadence high, particularly in the highest gears and when applying more than a little power

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      #3
      Thanks AZguy, I think your right, the chain stay has marks from the chain hitting it probably from skipping across the teeth. I'll measure the chain to check for stretching but unlikely, it's only a week old with less than 20 miles on it. At higher speeds the gears spin out, can't pedal fast enough to keep up with the speed. Might need a larger chain ring up front.

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        #4
        If the chain is good then it's likely just the small cog - again don't expect anything visible, they can be bad without it showing

        I'd consider going to a cassette with steel cogs although just the aluminum 11t cog are available and inexpensive

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