Bicycle Mechanics - shimano rapidfire

I have an early 90's mountain bike that I'm trying to get ready for a winter bike. It has Shimano Rapidfire shifters (two thumb levers on the front). I discovered the front shifter won't hold its place when the thumb lever is depressed, but it moves the cable.

Is this something I can take apart and fix? I didn't see an obvious way to take it apart.

I tried a regular thumb shifter I had sitting around, but that was a no go. The spring mechanism on the front derailleur must be different somehow from a regular derailleur.

I thought about just finding a cheap front derailleur for it, but I'd prefer to work with what I have if I can. I suppose I could set the cable so it's on the middle ring and run a 1 X 6 (might be 7, can't remember).

I have an early 90's mountain bike that I'm trying to get ready for a winter bike. It has Shimano Rapidfire shifters (two thumb levers on the front). I discovered the front shifter won't hold its place when the thumb lever is depressed, but it moves the cable.

Is this something I can take apart and fix? I didn't see an obvious way to take it apart.

I tried a regular thumb shifter I had sitting around, but that was a no go. The spring mechanism on the front derailleur must be different somehow from a regular derailleur.

I thought about just finding a cheap front derailleur for it, but I'd prefer to work with what I have if I can. I suppose I could set the cable so it's on the middle ring and run a 1 X 6 (might be 7, can't remember).

Try flushing it with WD40 or LPS-1 and then exercise the shifter. This will soften any hardened grease.

Brad

Try flushing it with WD40 or LPS-1 and then exercise the shifter. This will soften any hardened grease.

Brad

+1, WD-40 flush will work about half the time for these old shifters that are "dead." Be patient with it, spray it into the shifter pod, work the shifter as bradtx says, do this a few times and if it's still not working flush it and let it sit overnight. If that doesn't do it, seven speed Rapidfire shifters are very inexpensive. We sell a lot of them at our shop, a LOT of bikes from this era have what we call "dead shifter syndrome."

Guess I'll try the WD40. Wish I should have done that before I put on the thumb shifters. Although for winter riding, I prefer non-indexed shifting so I was hoping it would work.

When you say inexpensive, what are you talking price-wise? I couldn't find a replacement online for less than $20.

I tried a regular thumb shifter I had sitting around, but that was a no go. The spring mechanism on the front derailleur must be different somehow from a regular derailleur.

Friction front thumbshifters work with practically any front derailler. Did you align FD with smallest chainring, pull thumbshifter towards rider, then connect cable?

Try shooting some aerosol white lithium grease into the shifters and work it in. It has a bit more body than WD-40 and contains a solvent which will help break down the old hardened grease. There are several brands available in your local home center or auto parts store. If all else fails, Falcon thumb shifters will definitely work and are very cheeep.

When you say inexpensive, what are you talking price-wise? I couldn't find a replacement online for less than $20.

If $20 for shifter(s) isn't your idea of inexpensive, we're not speaking the same language, sorry to mislead.

Friction front thumbshifters work with practically any front derailler. Did you align FD with smallest chainring, pull thumbshifter towards rider, then connect cable?

Yes, I did. The thumb shifter moves the derailleur, but the spring seems to push it back. I can hold it on the middle chain ring by tightening the tension adjustment on it, but not the top on. I didn't put it on a stand and try to diagnose it, since I was running out of time. I figured it was one of those things that aren't compatible. If it should work, I'll give it some extra time.

If $20 for shifter(s) isn't your idea of inexpensive, we're not speaking the same language, sorry to mislead.

On a bike that I bought 2 for $30 with the intent of having one bike and one parts bike, $20 is expensive :) It just so happens I had enough other stuff lying around, I thought I would try to make both of them usable at the same time.

Try shooting some aerosol white lithium grease into the shifters and work it in. It has a bit more body than WD-40 and contains a solvent which will help break down the old hardened grease. There are several brands available in your local home center or auto parts store. If all else fails, Falcon thumb shifters will definitely work and are very cheeep.

I'll try the lithium grease this weekend since I already have a can. I soaked it with WD40 last night with no results. Though maybe letting it sit overnight would help.

On a bike that I bought 2 for $30 with the intent of having one bike and one parts bike, $20 is expensive :) It just so happens I had enough other stuff lying around, I thought I would try to make both of them usable at the same time.
$20 shifters are pretty close to the bottom. I routinely use the Tourney seven speed thumb shifters as replacements on MTBs, cost me $13 with cables and housings. But by the time you add shipping, you are pretty close to the $20 mark. I rarely pay over $20 for a mtb myself, but those are typically in the need TLC condition, and the shifters are often toast. Some can be revived, some are dead.

Depending on your definition of "winter", indexed shifting may be a bad idea for a winter specific bike. I changed my 7-speed lever switches to friction shifting a couple of years ago, and I'm not in any hurry to go back to indexed shifters. Friction shifters are much more reliable in really cold conditions, in my experience.

Depending on your definition of "winter"

Occasional overnight snowfall of around 12" (usually 3-4")temps between 15°-20°F most days.