Started off my ride the other day and found that the RH lever (rear mech)downshift and was staying forward after a downshift. It only took little pressure to get it to go back into the correct position. Anyway I figured that perhaps undoing the nice allen bolt on the underside of the lever might let me get a look at the mechanism. Within about a turn there was a little 'ping'and all seems well with the lever's movement.
The only thing is it seems impossible to re-tighten the allen bolt that goes throught the underside of the lever – it just spins. Gear shifting works fine now but curious to know if I've undone something crucial and is likely to work loose properly whilst riding leaving me with no gear change. Any views?

post a pic of which shifter type it is and i may well be able to help you.

remove the cable – the head has probably folded over and not sitting right in its housing anymore

my missus bike did this yesterday after she shifted and the mech didnt take the slack as it was bent (she hit it) so the shifter and the mech seemed to be busted !

GeeWavetree: it's one of these http://www.merlincycles.co.uk/mountain-bike-gear-levers-shimano-and-sram-gear-levers/sram-x7-trigger-shifters.html.

Any views?

trail_rat: thanks wil have a look but it's shifting fine and across the whole cassette so don't think it's that.

Cheers