Chain coming of chainring afrer new motor?

[Perryqhill]

Hi all. Just had a new e7000 motor fitted to my Kona Remote under warranty by my local service centre. On picking up the bike today the mechanic spoke to me saying my chainring was quite worn and that it should be OK for this chain, but would likely need replacing for the next one. Didn't think too much of it as it was fine up until the motor died, left and that was it.

I then took the bike out earlier and in higher gears it was atrocious, with the chain coming off the front chainring and doing allsorts of stuff jumping around and trying to get stuck. So I nursed the bike back home to have a look.

Firstly the bike has 460 miles on it. Its on a shimano deore cassette and derailleur that's done around 420 of those miles. A shimano chain that's done around 20 miles and the original FSA megatooth chainring.

So I went back home and started by aligning the derailleur hanger incase it had been bent. I then cleaned and degreased the drivetrain, then lubed the chain. I wasn't sure if the chain was maybe a link or two too long so I took two links out and tried it again and it was still doing it.

I then decided to set the derailleur up from scratch and adjust the gears, but again it was the same.

I can't see any stiff links, any twist or issue with the derailleur (it's actually worse under load and with the clutch on) nor any damage on the chanring and it's only really an issue in the smallest four cogs.

The obvious thing then is to replace the chainring as the mechanic said. However I've added pictures of mine and an original chainring the same as mine because the 'sharks teeth' he was talking about Is (unusually) what it pretty much looks like from new.

I've give up for tonight and put it away, but can anyone give anymore insight or is there anything when fitting the new motor that could cause this?

The obvious thing I suppose is to take it back, but given the hassles I've had with them over warranty I'm slightly reluctant to use them further and the mechanic has already given himself a get out mentioning the worn chainring anyway.

 

[Perryqhill]

Oh and a bit more information- when the chain comes off, it starts at the top of the chainring, doesn't sit right and then continues around and is then pulled off the chainring towards the crankarm.

Really don't think the chain is sticky, could it simply be the chainring is overly worn and isn't gripping the chain?

 

[Mikerb]

No chain guide??

Check the chainline...............the chain should be straight when on the middle cassette cog. If that is not the case either the chainring has the wrong offset or possibly a washer/spacer behind the spider ( if indeed there was one) is missing.
I assume the bike shop had no need to remove your cassette for a motor change so that should be OK assuming it was assembled correctly initially.

Usual reasons for a chain coming off the chainring are mech clutch not working or chain too long, or incorrect chainline.

 

[Mikerb]

Oh and a but more information- when the chain comes off, it starts at the top of the chainring, doesn't sit right and then continues around and is then pulled off the chainring towards the crankarm.

Really don't think the chain is sticky, could it simple be the chainring is overly worn and isn't gripping the chain?

a worn chain normally causes chain suck...ie it does not release at the bottom of the chainwheel. If the chain is coming off at the top of the chainring I would suspect one of the issues as in my post above.

 

[Perryqhill]

No its never had a chain guide, maybe something I could look at.

Chain length actually seems better now than it was. After removing a couple of links.

It actually seems to get worse with more torque going through it / with the clutch on.

 

[Perryqhill]

a worn chain normally causes chain suck...ie it does not release at the bottom of the chainwheel. If the chain is coming off at the top of the chainring I would suspect one of the issues as in my post above.

I can't get my head around the difference. Pre new motor - not a single drop over 460 miles.

New motor - horrendous. I think it may be something to do with chain line or an issue somehow with how it's lined up, guess I'm just looking at ideas and need motivation to start again tomorrow.

 

[Mikerb]

On any 1x system the chain is at its most extreme angle to the chainring on the highest and lowest gears. To minimise that thee chain should be straight in line with the chainwheel when on the central cog of the cassette. So that is something you should check first. If you find that is not the case then the chainwheel or spider are the main suspects for being incorrectly fitted.

 

[Perryqhill]

Had a look at the chainline last night. 10-speed and looked fine in middle cogs. Was thinking over and over and decided it must be, at least in part clutch, chain, maybe the worn chainring playing a part too.

Started off today by looking at the length of the Shimano HG54 chain again as I purposely had left it a fraction longer when first fitted (but took two links out last night). Sizing looked good, checked for damage or sticky links - couldn't find anything.

Then took the derailleur off and cleaned it, then serviced the clutch - no difference.

When cycling the chain last night I'd mentioned it was coming off at the top, but when it cycled it backwards it came off at the bottom. I then decided to try my old KMC X10 chain which was worn a little more than I'd have liked, but was taken off two weeks before my motor had died. First spin it came off again and I sighed - but then it was OK....

By this point I'd already decided to buy a new front chainring anyway just to have as a spare. So I thought about running the current chainring, cassette and old chain till the chain gave up and then just replacing all of it.

I then remembered I'd taken an almost new Sram chain off a recent back up mtb I'd bought when I'd put a bigger rear cassette on. So I found that, but damn it was two links too short and no good on the 46t. I then found two 10 speed kmc quick links and got a 10 speed inner from the HG54 chain and bingo a frankenchain was born.

So cycled it through the gears on the stand and it was OK, then took it out and done around 18 miles and it seems to have cured the problem.

Not sure what to do next. It's only 10 speed with a shimano 11 46 rear cassette on so not massively expensive. I'm going to order another KMC chain. Debating whether to try that straight away on current cassette and chainring or buy a new cassette, chainring and KMC chain and just keep them till the current set up gives me problems.

Not sure what's happened to the HG54 chain, but it is seems to have been the issue some how and it was fine before the motor died.

 

[TommyC]

I had a similar issue when my cube was new. The stock chain ring was an ethirteen one. After speaking to cube and e13 it turned out to be a known problem. E13 contributed it too ‘a number of factors’ but ultimately supplied a new chainring with a 1mm spacer. So it was a chainline issue.

Maybe your chainline has shifted somehow? Or it had a spacer and doesn’t now?

I never actually fitted the ethirteen one as I’d already fitted a hope chainring, which had chunkier teeth, that cured the problem. I now have a Pilo chainring that the bike shop also sent as a replacement for the stock one. Chain hasn’t come off once.