I recently bought a BH Lynx 6 electric mountain bike and so far have been having struggles getting it riding well. After getting it here and setting it up I found that in the highest gear (smallest sprocket) I would have the chain jumping / skipping while riding. It was worse at higher power outputs and things like climbing hills, but it would do it occasionally on the flat too. Shifting down a gear I had no problems. The bike has a Shimano Deore XT 1x10 drivetrain.

I tried adjusting things with no luck, but did find if I backed the b screw out a ridiculous amount that seemed to fix the problem. But at that point I could only use 8/10 gears so not a great solution. I gave up at this point and took it to the local mountain bike shop that also sells electric mountain bikes. They did a tune up and adjustment and gave it back to me with exactly the same problem. I took it back to them and pointed this out, and then worked on it some more and told me that the issue was that the chain was too short and they put a longer chain on saying it would let them get more chain wrap.

I picked it up this time and it did indeed seem fixed. Later that day I went on a ride and it was great for the first 5 miles and then it started up again even worse than before. Now it did it in the top two gears instead of just the top gear, and it also seemed like the chain was grabbing the next sprocket on occasion too. It was also doing this with gentle pedaling on the flat even with the motor off. I limped home and rode around the block a few times trying to verify the chain was indeed catching the next sprocket, when it caught the next sprocket and sheared off a link and broke the chain.

So now back to the shop, and they told me this time the issue was that they didn't use an "ebike rated chain" which they had to special order. That came in and they called and said they've adjusted it as best as they can but that the issue is that the smallest sprocket just doesn't have enough teeth to handle the torque of the motor and that it's a design flaw and there's nothing they can do. I find it hard to believe they'd sell bikes with this sort of flaw, and the motor isn't that powerful. Plus I was able to get it to do this with the motor off while standing on the pedals up a gentle hill, so I'm not sure how the motor power could be the issue...

I'm feeling pretty stuck at this point, and it seems like the shop has given up. Short of just not using my top gear, does anyone have any advice on what I might be able to try?

  • Can you post a couple of pictures, of the sprocket itself (taken from the side of the bike), and the derailleur alignment while it is engaging the sprocket in question (from the back of the bike towards the front)? Is this skipping like the chain skips on the teeth of the same sprocket or rather it tries to go one cog up and falls back again? According to this site, the so-called "electric bike chain" has no special features comparing to normal chain, I started a thread on this topic some time ago. – Mike May 14 '20 at 6:27
  • Check the chain for a stiff link. – Carel May 14 '20 at 7:47
  • Professional cyclists also have professional mechanics instead of someone who picks a screw and turns it by ridiculous amounts. And the motor for that bike is advertised as 550 watt. – ojs May 14 '20 at 8:07
  • ah, quite a bit more powerful that what I was expecting. Also missed the second paragraph when I scrolled down the page. – el_oso May 14 '20 at 8:44
  • I'd find a better mechanic! – Carel May 14 '20 at 10:26

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