OK, I finally got chance to investigate further following the advice given to me on this thread
As far as I can tell, there's nothing loose anywhere. What there is, though, is a surprising amount of wear on the chainwheel. Bear in mind that these snaps are taken with the bike upside down ...
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7714_zps6bbadeb8.jpg
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7695_zps9408d85a.jpg
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7694_zps5ce10323.jpg
That burr on the trailing side of each tooth is quite pronounced (maybe 25 thou or more), and just turning the cranks by hand against some resistance from the back brake produces a definite "snatching" and tendency for the chain to hang up, which might well translate into the "knocking" I'm getting when pedalling with power on.
I'm not entirely sure that I've found the cause, but obviously I need to do something about this! The first question is, though, is that amount of wear considered normal after 18 months and just 1600 miles?
Whatever, it's time for a new chainwheel, the fitting of which looks to be a straightforward job (?) and obviously a new chain to go with it, but what do you guys reckon to the wear on the motor sprocket? Leave it, turn it round, or replace it?
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7708_zpsde6ae482.jpg
ETA - just to clarify my original post in that other thread, the muffled knock/clunk/whatever is definitely getting worse and more frequent, but it's only heard - nothing's felt and nothing "gives" when it does it, like it would if the chain was jumping a sprocket ...
As far as I can tell, there's nothing loose anywhere. What there is, though, is a surprising amount of wear on the chainwheel. Bear in mind that these snaps are taken with the bike upside down ...
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7714_zps6bbadeb8.jpg
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7695_zps9408d85a.jpg
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7694_zps5ce10323.jpg
That burr on the trailing side of each tooth is quite pronounced (maybe 25 thou or more), and just turning the cranks by hand against some resistance from the back brake produces a definite "snatching" and tendency for the chain to hang up, which might well translate into the "knocking" I'm getting when pedalling with power on.
I'm not entirely sure that I've found the cause, but obviously I need to do something about this! The first question is, though, is that amount of wear considered normal after 18 months and just 1600 miles?
Whatever, it's time for a new chainwheel, the fitting of which looks to be a straightforward job (?) and obviously a new chain to go with it, but what do you guys reckon to the wear on the motor sprocket? Leave it, turn it round, or replace it?
http://i79.photobucket.com/albums/j158/danfoto_photos/IMG_7708_zpsde6ae482.jpg
ETA - just to clarify my original post in that other thread, the muffled knock/clunk/whatever is definitely getting worse and more frequent, but it's only heard - nothing's felt and nothing "gives" when it does it, like it would if the chain was jumping a sprocket ...
Last edited: