Cycling Through History has a new website!
Please updates your links and RSS feeds. This site will stay up but will not be updated after December, 2012.
Shimano flatbar shifters have a tendency to age poorly. There are a couple of reasons for this. The more destructive reason, and the less fixable, is that something in the shifter itself is broken. It happens. The insides of these things are mostly plastic these days and sometimes the teeth on the pawls get stripped, or you manage to snap something to small pieces during some epically mistimed upshift. We've all been there I suppose.
The more common reason these things stop working, and the one that you hope happens to you, is that the grease inside has solidified into something resembling brown taffy. The good news about this particular problem is that it's more than likely fixable.
Here's how we break down the diagnosis....
-A customer comes into the door and says something like, "Sometimes when I shift it doesn't feel like there are any clicks. The lever just moves and nothing happens."
-You, being the expert at bicycle maintenance that you are, inspect the bike. Does the shifter fail to engage? Or does it engage inconsistently? If so, huzzah! Take the bike from the customer, tell them it will be ready by tomorrow, and then whisk it away to the back.
-Hose out the shifter with Speed Clean aerosol degreaser, or something similar. I like residue-free degreasers for this job. If you can open the shifter, or remove part of the cover, then so much the better. If not, put the nozzle into the derailleur cable hole and let 'er rip.
-Immediately begin shifting the bike enthusiastically. If the stars are aligned then the shifter will wake up and start to work better almost immediately. If not, it may take a couple of hosings or letting it soak overnight to break down the grease further.
Hopefully this solves the problem. There are a handful of times when I have tried this remedy that it has not worked. If it's a nicer shifter (LX, XT, etc.) then you can usually take the thing apart and have full access to the shifter mechanism. This makes cleaning it out much easier.
Time for a horrible explanation with next to no visuals because I'm not that tech savvy. The shift levers wind the shifter internals, which are held under tension by a spring. The clicks in the shifter are caused by detents in the shifter internals. There are a pair of spring loaded release catches attached to the shift levers, and it is these catches that click into the detents and hold the internals in place. If you take a shifter apart the two catches will be really obvious. You'll see them as soon as you start clicking the shifter around. Gunk tends to get built up on these catches and they can bind. Find them, blast them with degreaser, and then use a small pick to manually move the catches on their pivots. This has revived shifters that I thought were total goners. This is a repair of last resort though, and since it's time consuming and not a sure thing you should probably only try this on shifters that the customer is completely unwilling to replace.
But you should also ask yourself something...Why are you trying to revive these shifters? If you're doing this repair then they already meet two of the three criteria in my trifecta of standards that almost guarantee replacing the part (#1, "Old and nasty", #2, "Broken". #3 would be "Unsafe"). There are good reasons to try and do this for a customer, but there are equally valid reasons to not do this and simply replace the part.
This repair should go one of two ways. First, you could restore some function to a part that would ideally be replaced. You need to use your judgment whether or not this is a good idea and whether or not the customer will be best served by reviving a used part. Sometimes we do this to be nice, others because of a customer's budgetary concerns. Second, you could replace the shifter (and cable since most new shifters come with a new derailleur cable attached), and more than likely improve the shifting performance for not that much money. It's up to you to decide whether or not your time is better spent fiddling with old broken parts or selling new working parts. You also need to know your customer well enough to know whether or not they're ok with the potential for marginal functionality in an old rehabbed shifter, versus the guaranteed shifting performance of a new part.
So there ya go. Be sure to only use your new-found knowledge for good.