Chain coming off?

[Nealh]

Older style mech's don't have a clutch to prevent chain slap/tension issues but worth John checking chain length first as has been suggested.

 

[John Cee]

Give them a call or owner David will be here soon, they will help you out with your issue.

They've been helpful with another issue (much shorter battery range than advertised/expected, intermittent loss of power) which is sort of ongoing.
But regarding the chain, it seems like the sort of thing I could probably sort out more easily/cheaply by doing it myself rather than taking the bike back which is a bit of a faff,
All replies have been very helpful, thank you!

 

[John Cee]

If the chain is falling off the front cog, how about trying one of these.

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xchain+guide.TRS0&_nkw=chain+guide&_sacat=0

Works for me.

I'd thought about this, but thought the manufacturer would have fitted one if it was necessary. Will revisit the idea if the new chain doesn't help. Thanks for the suggestion!

 

[JPGiant]

Be careful when altering the B screw. It's the least critical of the 3 adjusting screws on the RD but, when set incorrectly it can cause either clatter between the RD upper jockey and the largest gear on the cassette or bad indexing between gears.

As others have said, the main reasons for the chain coming off is an overlong chain,

incorrect ​

chain line, faulty BB, or possibly a sticky chain link (not following the cassette teeth correctly) or maybe an over-wide chain link.

 

[Nealh]

I ride 2 bikes with single front ring and the only time I drop a chain is on really bumpy ground, the only other times I have an issue is with a damaged/broken link.

 

[John Cee]

Replaced the chain this evening, and while doing so found what I think is the real source of the problem. The bike has a chain guard attached to the chainring which I think is intended to prevent the chain coming off. However, I noticed that there were spacer washers fitted to the chainring retaining bolts that gave sufficient clearance between the chain guard and chainring for the chain to fall down between them. Removing the spacer washers leaves plenty of clearance between the chainguard and chainring, but now the chain can't fall off between them, So job done, I think.
Thanks to all for the helpful suggestions,
Cheers
John