gr8fzy1

Hello all you people more knowledgeable than I am. ^///^

I'm having a bit of trouble with the shifters on my mountain bike. I'm currently Riding a 21 speed Mongoose Alta mountain bike with Shimano Alivio shifters. They are a bit on the OLD side, so I'm wondering if anyone could tell my why they might possibly be refusing to shift the rear mech back up to first.

They shift down just fine, but once I try to shift back up, it feels like the gears/ratcheting mechanism in the shifters won't engage. Is this a lubrication problem or are they completely worn out? Currently my 21 speed is stuck as a 3 because I can only shift the derailleur on the crank.

CACycling

Most likely lubrication. Flush the shifters out with WD40, PB Blaster or other solvent. Hit them a few times and let them soak for a bit between dousings. Should free things up and get you shifting properly.

BCRider

Over time the cables tend to cut tight fitting grooves into the liner plastic in the cable housings. When that happens the pinching can prevent them from moving easily and in extreme wear conditions perhaps even stop them from moving altogether. If the bike is quite old and well used I'd suggest new smooth finish die drawn cables in new shifter housing in addtion to flushing clean and lubing the shifter pods and derailleur pivots as CACycling suggested. And it's best to replace them since if they are worn in this manner oiling or greasing the cable is too little too late.

Re-Cycle

I'm with CACycling's reply. The ratcheting pawls in standard mountain bike trigger shifters become stuck if they were not used for a long time. My guess is that the grease on the pivots coagulate and stick the pawl in the out position. Along with the WD40 drenching I would suggest trying to disassemble or somehow get to those pawls. If you can work them back and forth by hand they should eventually start moving freely.