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Brompton M6L, clunky feeling and noise

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Brompton M6L, clunky feeling and noise

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Old 05-06-18, 08:12 PM
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hhk25
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Brompton M6L, clunky feeling and noise

I have a 2017 Brompton 6 speed with only about 400kms on it. When I'm in the larger cog, pedaling feels rough. I can hear a very subtle "clunk" noise 6 times per pedal revolution, always in the same place in the stroke. I thought the chain was rubbing on the plate inside of the cog (wing plate?) but that does not appear to be the case.

The derailleur shifts properly but the drivetrain does not feel smooth. In the smaller cog, it pedals fine.

Any ideas?
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Old 05-07-18, 02:47 AM
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badmother
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Is the wire shifting between the two cogs properly adjusted? Wires stretch with use so after some time the gears are no longer properly adjusted. Search Youtube for a video or two explaining how to do it. Report back
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Old 05-08-18, 12:52 PM
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veets
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If I'm understanding your description properly, it sounds similar to what I experienced after changing a flat and removing / reinstalling the rear wheel. It turns out that the derailleur was not seated properly. I was surprised just how much slack there was, and still shifted properly and it hadn't fallen off! After snugging it up properly and tightening the bolt, everything was fine. As unlikely as it might be after just riding 400km, you might check the derailleur to see if it's seated properly.
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Old 05-09-18, 09:33 AM
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hhk25
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I was able to fix this using Brompton's service bulletin: https://trade.brompton.com/Uploads/Q...ets/ds-cta.pdf

The problem was the chain pusher contacting the idler wheel. The idler wheel has a "spoke" design and the six clunks per pedal revolution was the pusher hitting each of these spokes.

It helped a lot to mount the bike upside down on a work stand and then use the limit screws so that there was a tiny bit of daylight between the pusher and idler wheel. Both on the high and the low side.

As an aside, I find Brompton's Youtube video on this woefully inadequate. The video itself is out of focus and the video covers too many different adjustments.
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Old 05-09-18, 12:08 PM
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Schwinnsta
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Thanks for the follow up.
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