My wife has a hybred bike (sort of a light duty mountain bike). The front derailer is out of ajustment so the bike will only go in to the lower 2 of 3 gears. (The chain just wont engage the largest sproket which is they tightest cable tention).
As far as I can tell there is 4 ajustments that can be made:
1 a stop pin for the innermost position (smallest gear/slack cable) the derailer can get to
2 a stop pin for the outermost position the derailer can get to
3 a hand ajustment to shorten/lenghten the cable (right at the shifter)
4 the cable itself can be ajusted for lenght where it ataches to the derailer.
Am I missing some ajustment? how should I go about fixing this?
I would hang the bike from the ceiling or something so you can rotate the pedals and rear wheel freely. Then back off the stop for the large chainwheel until the chain can freely jump up to it reliably as the pedals are turned. Adjust the stop so than the chain can’t move far enough to go past and get caught between the chain ring and the guard, if you have one. That’s basically it as far as I can remember.
Pull on the cable by hand to see what, if anything, is blocking it. If the derailleur has dropped to low for some reason, the middle ring may block it from shifting all the way out. If you still can’t fix it, try this site, or this board.
You might want to adjust the whole thing from the start … here’s some quick guidelines, though the site linked by zwaldd has detailed instructions.
The stop screws should be set to prevent the chain from slipping off either side.
Set the rear derailleur to high gear for the smallest ring, and low gear for the highest ring, adjust the screws and turn the crank when adjusting. You should be able to tell which one sets which, or they might be labelled (L for the smallest ring, H for the largest one).
Adjust the low one with cable completely slack, or when the cable is tightly pulling (on the high side). Don’t use the shifter; you want to the cable to be completely slack (for the small ring) and pulling tightly (for the large ring) to be safe.
Since you have two adjusters, do this with the shifter (part at the handlebars) – set to lowest gear, unscrew its adjuster all the way out (allowing the most cable), then back in one turn. Make the rest of the adjustments on the cable at the derailleur. The rationale for this is that normally, the cable stretches, so you only have to add tension over time at the shifter.
Set the rear derailleur to middle gear. With the front derailleur in low gear, take in slack in the cable at the derailleur (loosen and pull through the screw if necessary); this doesn’t have to be perfectly tight. If you end up with a whole lot of excess cable, cut and crimp (if you have the tools) or replace the cable (this would be a sign that the cable’s old and worn out).
Set the front to middle gear; adjust the cable so that the chain stays in the middle gear when the shifter is set to it without rubbing the derailleur cage. Test to see that you can shift properly to low and high gears. (keeping the rear in the middle gear).
It’s best to test final adjustments by riding it, as the weight of the rider may change the necessary adjustments. It’s rare (unless you have a really good bike) for the derailleur to be perfect in every gear, so adjust it for the way it’s normally ridden.
panamajack don’t think your words went to waste, after all you did a lot of typing. I did a complete ajustment as in the above link, I used your post as a double check to make sure everything is right.