Gear adjusting

[Plax]

I've got an old bike I'm going to sell on ebay. However I can't get the gears to work properly. At the chainwheel, it goes from the high chainring (3) to the low chainring (1) but won't go from the middle chainring (2) to the the low chainring (1). At the rear wheel it will go through all the different sprockets no problem on all three chainrings. So I therefore think the low and high adjustor screws on the rear mech are okay, and that I also don't need to do anything further with the adjustor barrel (I did play with the adjustor barrel initially but then the chain jumped off the top chainring etc).
Could it be that the high and low adjustor screws on the front mech needs adjusting? I do recall fiddling with everything at one point even the front mech. Any alternative suggestions if this isn't the case?

 

[PatrickPending]

Try

http://www.sheldonbrown.com/derailer-adjustment.html#front

good luck!

 

[Paulus]

Maybe the cable is a bit too tight and need slackening off. You may need to loosen off the pinch bolt on the front mech with the chain on the smallest chainring and pull/release the cable until there is no slack, but not too tight Then start with the adjustment. if then it still will not change onto the small ring then the stops may need slackening off. Thoughly clean the mech to get any dirt, rust, crud out of the way first and then have a go at the adjustments.

 

[gbb]

Check your cables are actually free running.
I had a similar problem...couldnt adjust a mech properly. Took the whole cable out and realised how much corrosion / crud was inside. Cleaned, lubed, worked like a good un then.

 

[Plax]

Well after a bit of fiddling of the front mech I can move the chainrings down from top - middle - bottom but not from bottom - middle. It'll occasionally go from bottom to top. So the reverse problem now! . I've obviously got the lower adjustor screw at roundabouts the correct point. No amount of playing seems to be able to make the high limit screw work in my favour though. The rear sprockets all work fine still.
I hadn't thought about cleaning the chain. It is pretty clean as the bike has never been ridden through any mud or in rain. maybe I'll double check the cables, give them a quick blast of lube and clean the chain anyways and see if that makes any difference.
Do you still think loosening the cable would make any difference?