Bicycle Mechanics - knackered shifter

Does anyone know how to fix up these things ?

It won't change gears easy, and won't go into top at all. It's one of those new type, thumbshifter with two levers 'Shimano Altus'.

I can't figure it out, all the bits are hidden away.

There are 2 little screws - almost the size of watch screws - undo these and the cap covering the mechanics of the unit comes off.

I wouldn't mind betting that the cable end has popped out of it's holder inside the shifter. We get this problem all the time in work - normally caused by people shifting/messing about with the lever whilst not pedalling.

Before you dismantle the shifter, check the limit screws on the derailleur mechs, and check that the cable is properly attatched to the mech.
Dismantling shimano shifters is a fun thing to do, they are full of springs and little plastic bits that pop out.

If the shifters/bike are new and you got them from your LBS get them to check it out. They will probably check them at no charge, and if there is a problem it may be under warranty. If the bike is new you may just need adjustment which your LBS should do, assuming you got the bike there.

Originally posted by john999
Does anyone know how to fix up these things ?

It won't change gears easy, and won't go into top at all. It's one of those new type, thumbshifter with two levers 'Shimano Altus'.

I can't figure it out, all the bits are hidden away.
This just happened to me. I thought it was just a loose shift cable. But the bicycle repair book I had I bought in the mid or early '70s soo I went out and bought a new one that covered detent shifters. Guess what it was a loose cable. No problem I'm enjoying reading it and some stuff is new and/or different.

Short of it check the cable before you start turning screws for the limit adjustments.

Joe
:beer:

Well I took it apart and the pawls aren't catching on the ratchets.

It looks like the little springs that hold them against the cam are worn or out of position.

Is it possible to replace these ? How do you get them out or dismantle the shifters ? It looks like the whole assembly is held together by metal pins pressfit onto metal discs.

If the shifter is a couple of years old, the grease that lubed the pawls is now gummy. The grease is causing more friction than the pawl springs can move. Put the shifter cover back on and squirt inside the shifter housing some foaming degreaser (I usually use Tri-flo degreaser but it needs to foam up to penetrate). Repeat until it works usually two or three times. Then lube with your favorite oil.