I have a well-used Trek 520 that still has the original 7-speed RSX brake/shift levers. The right-side lever sometimes doesn't catch on the downshift action unless I put a little pressure on the lever in the braking direction or otherwise wiggle it around. It's an intermittent problem, though the lever did fail to downshift at all during a cold snap we had here a week ago. As soon as the temperature got above freezing, the lever began to work again. Is this a problem that can be solved by any cleaning or adjustment, or is this what can be expected when combo levers begin to wear out? I have a set of bar-ends that I can install, but it seems a waste of good bike parts if the combo levers can be made to work properly again. I don't have any experience with servicing these levers, so any thoughts or advice would be much appreciated.

Cheers!

Since downshifting to bigger cogs is more positive than shifting to smaller gears,it could be the lever is toast. Shifting to smaller cogs is totally dependent on spring pressure in the derailer, and stiff lube in the shifter,casing or derailer can cause problems.Check for a loose screw on the upper backside of the levers that holds them together. Other than that you can try hosing it out with a solvent that won't hurt plastic(wd-40,) and relube with a spray lube.Otherwise,they are not servicable other than a return spring immediately under the levers.