Riding with a slightly oversized chain

[Punkawallah]

See? ‘If it ain’t broke’ :-)

I’d venture the shorter chain is tauter, which would affect how efficiently the derailleur moves it from one gear to the next. There will probably be a adjuster on the derailleur where the cable enters?

 

[Ajax Bay]

I’d venture the shorter chain is tauter, which would affect how efficiently the derailleur moves it from one gear to the next. There will probably be a adjuster on the derailleur where the cable enters?

First of all,
I wonder if you'd care to explain which section of the chain will be "tauter" (aka greater tension) if a chain is short or long, and how that would affect shifting? How would the existence of a cable clamp adjustment barrel (nearly all rear mechs have them) and its use be relevant to how long the chain is?

 

[Punkawallah]

Hi, no problem. The jockey wheel cage is sprung to take up slack in the chain. If the chain is shortened, the cage is pulled against the spring. The spring is harder to compress the further the cage is rotated (at least on my Cyclone). Having serviced the Cyclone I know that a ‘slack’ spring gives a slack chain, and affects my gear change. Therefore I ventured that -extra- chain tension could be the reason the OP gear change was affected, and the cable adjuster might help remedy this by changing how the chain is moved across the block to change gears. Of course, this may not be the case, hence ‘venture’.