Bicycle Mechanics - Need help fixing gears

So I got my girlfriend a cheapo 18 speed mountain bike used. It works great for her needs but the gears for the front aren't working. It is a twist grip style shifter and basically the shifter won't twist. I've tried pretty hard to twist it and it just won't go. the back works just fine. Any advice on where to start on fixing the problem?

The place to start is by giving us some kind of useful information on which we can base advice: brand, model, age, physical condition and what you've already tried.

Is it jammed, or rusty? Did you cut or disconnect the cable to determine if the problem is in the shifter, cable front derailleur?

Basically we're not psychic, nor do we have x-ray vision that works through the internet. We need useful information in order to help.

What model are your grip shifters? What gear does it say its stuck in? And which chainring is the derailer/chain stuck on?

FBinNY has the right first step from our perspective- disconnect the cable from the derailer. Somewhere on the derailer will be a screw that pinches the cable. Release that screw a few turns (until the cable comes loose), then try to activate the shifter.

OK, so it is a eco terra bike. It is stuck on the smallest front sprocket. It is a quickshift qs60-61. I tried searching various places for advise on where to start with no luck. I'm going to take the assembly apart here shortly. I'll look for the screw that you mentioned, that may be my best bet. I need to redo the brakes as well, they suck but that will be an easy fix. I'll take the cable apart for the shifter.

A lot of those twist shifters are throw aways. Worth a try to rehab.

You MAY be able to check the front derailleur without disconnecting the cable. Find the section of bare cable that attaches to the front derailleur, and pull on it. If it tries to move the derailleur, this is a good sign. This works best if you have the bike in a repair stand, or have someone hold up the rear of the bike so that you can turn the cranks. Now if you can pull the cable while turning the cranks, you will find out if the front derailleur WILL shift to middle, or big rings. If this works, then I agree with wrk101--try to see if you can fix the twist shifter, but it may not be worth spending a lot of time, or any money on them. The low end components are often not made to be repaired.

Often the deraileurs on cheaper bikes are all steel and prone to rust/freezing. As the guys say, you have to isolate the problem. See if the DR moves at all. Disconnect the cable and see if the twist-shifter moves. If it doesn't, check the cable housing...It may be rusted. They don't put nice stainless-steel cables and housing on these cheaper bikes.

I bet the cable is rusted to the housing.

That is great advice. I can't really figure out how to get the cable off of the hand shifter. Rust would make perfect sense. I'll try messin with it down below. I'll follow up.

The cable is captive in the shifter with a little swaged on barrel end. The elbow at the twist shifter has a cover that comes off so you can replace the cable and feed it around the bend and then put the cover back on.

In any case even if my description is off by a little (but all the twist grip shifters I've had were like I described) there's pretty much nothing at all to rust inside that would hold the cable frozen in place. So check it over carefully for a little screw holding down a cover or a slide apart snap cover. And if you have to force it you're likely doing something wrong. Resist the lure of taking a set of vise grips to the thing in any manner at all.... :D

The derrailleur down by the cranks has two screws that can be set to control the limits of the travel. Just today I was helping out with a customer at my favourite LBS while the regular mechanic/server was busy. Seems that someone had screwed in BOTH limit screws to turn the bike into a single front speed. Or maybe they thought they were not supposed to be loose? In any event just backing those off restored the shifting. SOmething like this may be your case as well depending on who may have been tinkering with things or if someone decided on a little practical joke.

Twist-grip shifters are basically unfixable. When they break, you just buy a new one; they're not that expensive.

Twist-grip shifters are basically unfixable. When they break, you just buy a new one; they're not that expensive.

I've repaired my Sram 600's a couple of times. I probably should pick up some NOS 8-speed X-Rays before my 600's fail again, however.

Granted, the OP's bike is a Huffy. So it might be tough to warrant throwing even $30 at it. I'd imagine lots of rear shifters get killed before front shifters. With any luck front spacing on that Huffy is about the same as any other MTB in the last 20 years or so, time to hit the bike junk shops if you're in a city that can support that kind of business - then you might be able to pick up a left shifter for $5 or so.

If you go the rebuild route, have an assistant take LOTS of photos as you disassemble it. Even with these, the rebuild will probably take an hour or so. My first rear shifter Grip shift cable change took me about 3 hours. I didn't take pictures and dropped a couple of pieces which I shouldn't have, so it was rough getting it back to functional.

First remove the grip, careful not to lose the washer between grip shifter and grip, then loosen that teeny little allen bolt on the shift housing area where the cable comes out of. Carefully inspect as you pull the grip shift away from the shifter body. Look for rust, maybe just spray a bunch of Tri-flo in there and put her back together if it looked pretty nasty. Otherwise, slowly push the cable in 'til you can grab the end and pull it out, continue disassembly, see if you can see what's wrong then see if you can put her back together.

I'd say grab the front derailleur by the cage which surrounds the chain, and see if that moves. If so, then detach the cable which goes to the shifter from the derailleur and pull the cable and cable housing out of the eyelets which hold it to the frame until it's only attached to the shifter. The cable has a small metal disc cast onto the shifter end which simply fits into a slot somewhere on the shifter. If you can't see where, you probably have to unscrew a cover.

Try parktool.com, they might have instructions for working on twist shifters. Or try the local library for a book, in case you don't want to just start peeling stuff apart.