Chain skip smallest sprocket

[tinchy]

OK guys heres my issue:

- re done the bike after winter - new cables, mech, chain, cassette
- I find the chain skips every say 20s but only when riding in the big ring/smallest sprocket (i.e. top gear).
- There is absolutely no skip in any other of the sprockets.
- Doesnt happen under load as I can get off, pedal the bike with my hand and observe the chain skipping/jumping once every 20 odd seconds.


What do I need to do to solve this? My irrational brain says it may be a b tension screw issue on the rear mech (which is new), or a stiff link in the new chain? I cant imagine the limit screws would cause this, or at least Im having no problems when shifting in to the top gear from that perspective.



Help!


cheers

[jekyll man]

split link fitted incorrectly?
chain riding on the lockring?
shimano chain fitted upside down?
Freewheel binding?

[Irish]

A stiff link where you joined the chain.....

[tinchy]

I think this might be it yeah. If it is to do with the chain its definitely a stiff link and not a chain length issue as I used the same length chain as was previously installed...

[Calnago]

Not the b screw, that may come into play with the large sprockets but not the smallest.
Could be a stiff link in the new chain, especially where you joined it. Check and loosen if tight.
Could very likely be the high limit screw or cable tension too tight not allowing the derailleur to actually move over far enough. To check: Completely loosen the rear derailleur cable bolt to allow the derailleur to settle to its most outward position against the limit screw. Turn the cranks in the stand. Does it still catch a bit? If so, loosen the limit screw to see if you can loosen it enough so that it doesn't catch. If you can then that is your issue, or one of them. If the derailleur is slightly too close to the 2nd smallest cog it may want to catch the chain on the ramp. May be out of adjustment just enough to catch a bit there (annoying) but not enough to really notice it in the other cogs.
The other things to check are derailleur hanger alignment and cable friction. If there is any friction in the cable routing, this could hinder the derailleur from moving freely to its most relaxed position.

[tinchy]

I'm having doubts over the stiff link idea - if I pedal by hand until the chain skips then stop, the connecting pin is not close to the jockey wheels/cassette.

Is is possible there is a stiff link elsewhere in a new chain?!

[tinchy]

I think there must be a stiff link somewhere in the *new* chain.

I rotate the pedals by hand and stop every time it skips. The link pin is always in roughly the same spot, just at the top of the front chainring. No wmy reactions are good enough that I belive the chain is not skipping on the link pin but behind on some other link?

[mattr]

You should be able to see the stiff link as it passes between the top jockey wheel and the sprocket.

[tinchy]

Thats the thing, I cant seem to feel a stiff link even though the 'skip' seems to happen at roughly the same location

[Irish]

Turn the crankset in the right direction, then as soon as you hear the "click" reverse the direction and keep a looout at the area the sound is coming from, repeat this until you narrow the area down to a few links. when you have it narrowed down turn this area of chain so it's returning towards the rear derailleur, then take the chain off the chainring and hold the area of chain where you have located the skipping to be coming from, now bend the chain inwards and outwards (against the the normal direction of bend) this should loosen out any stiff links, if you used a connecting link check it has connected correctly on both sides, hope this helps.

[ayrej2]

Have you tried Calnago's suggestion on the limit screw - had the same thing myself with the chain just catching at one point and starting to shift but immediately dropping back down onto the little cog.

[tinchy]

Solved it.

I cant have cleanly broken the protruding pin from the inner side of the chain when installing. hence there was a slight bit of the pin still poking through on the inner side which was just catching with the cassette cog as it passed over it. sanded it slightly and problem solved

[Calnago]

Ah, that's why you install that pin from the inside out. Always. Never even thought to suggest that. Glad you found it.