Shifter repair advice.

[beenatitforyears]

Hope somebody can help. I'm in the middle of restoring a bike and the left hand (front) shifter is playing up. Its a shimano xt 8speed SL M-739.

The lever moves through the full arc and moves the mech one chainring and then stops. It will change down and up but only two chainrings.

When you change up the shifter stays at its full range and on the way only give one index click.

Any ideas how to repair it?

 

[drystonepaul]

Re:

First thing to try is to flush it through with some light oil like GT-85, WD-40 or my personal favourite Swarfega Duck Oil.

That should shift any dried out grease and dirt which could be fouling up the delicate ratchet mechanism. Cycle the shifter through it's full range of movement a few times without the cable installed.

You can do this by just removing the cable cover, but it's more effective if you can remove the whole lower shifter housing. You'll need some very fine and properly fitting screwdrivers for this. The screws are very small and easy to round out.

If this doesn't resolve it then inspect the ratchet teeth and rocker pawls for any damage.

On XT M739 shifters the ratchet mechanism is made from cast aluminium and is significantly more susceptible to damage than lower end shifters.

 

[beenatitforyears]

Thanks, I have given the flushing a go but no luck. Will leave it overnight to soak in and see if that helps.

If I undo the internal centre but to get a better look will I be able to get it back together?

 

[drystonepaul]

Thanks, I have given the flushing a go but no luck. Will leave it overnight to soak in and see if that helps.

If I undo the internal centre but to get a better look will I be able to get it back together?

Yes, there are still a few screws and bolts holding it all together once you've removed the lower covers.

 

[beenatitforyears]

Didn't work. Resorted to putting it into the dishwasher then giving it the lube of its life. Can get all three gears now. Still not self returning after a change but a quick flick sorts that out. At least I can ride it until I find another.

 

[Thias]

This "not returnung" is a broken Spring. I had that, too. It is repairable, but its hard to find a replacement.

 

[dyna-ti]

This "not returnung" is a broken Spring. I had that, too. It is repairable, but its hard to find a replacement.

Ive found pulling on the wire to simulate the rear spring helps after you flush it all out :? Had a shifter wouldnt return and went up in a double click.
Holding onto the cable and clicking up,then down etc etc helped considerably :? (so as you click it down you tug on the cable forcing it to change gear. If its a build up of hardened grease it could help shift it