Bicycle Mechanics - Gears jumping on fifth & sixth cogs

I was riding my PX10 yesterday and it the chain was jumping only on cogs 5 & 6 (of 6). I believe I've used the freewheel before w/o problems. I'll be checking the chain but - can a stuck link only bother the higher gears? What else should I check? It's friction shifting BTW.

Thanks

Cables/housings -- clean/replace?

Do you have a cable guide, under your BB shell? If so, clean it up well with WD/whatever, and make sure you don't have any friction, there.

Sheldon? Anything else??

http://www.sheldonbrown.com/autoshift.html

Have you measured the chain? Any 24 pin interval should measure 12 inches. If you let it stretch to 12 1/8th you may have ruined the freewheel, and a new chain will slip on some cogs, usually the smaller ones.

If you suspect a tight link, use your fingers to pivot each link around each pin until you find it. Carefully loosen the tight link slightly with a tool.

Al

Cables/housings -- clean/replace?

Do you have a cable guide, under your BB shell? If so, clean it up well with WD/whatever, and make sure you don't have any friction, there.

Sheldon? Anything else??

http://www.sheldonbrown.com/autoshift.html

Bike's clean and the chain and cables are new. I did put a different wheelset/freewheel on.


Have you measured the chain? Any 24 pin interval should measure 12 inches. If you let it stretch to 12 1/8th you may have ruined the freewheel, and a new chain will slip on some cogs, usually the smaller ones.

If you suspect a tight link, use your fingers to pivot each link around each pin until you find it. Carefully loosen the tight link slightly with a tool.

Chain is new. I was polishing parts for my Soma reubild tonight, but I'll throw the PX10 on the stand to check the chain links. It'd just be odd it runs smooth in the other gears.

Al

A stiff link will complain more on the smaller cogs since it needs to bend more as it travels over them. Watch the chain closely as it passes through the derailleur and over the cogs -- you should be able to isolate the problem link(s). Gasp the chain firmly and flex the problem link(s) sideways a few time to loosen them up. If that doesn't fix it, you may need to use a link spreader such as is found on the old Cyclo chain tools.

Bike's clean and the chain and cables are new. I did put a different wheelset/freewheel on.
This may be your problem. A new chain on a worn freewheel will often cause this problem. You need to use a new freewheel with your new chain.