Stuck twisty gear shifters

[CaptainSlow]

OK, I don't know what they're called...the twisty gear shifters similar to the one we had on our Grifters. Anyhow, SWMBO has a mountain bike that's been in the shed for a few years and I'm trying to resurrect it. The left shifter (FD) is ok but the right is stuck. The RD moves ok when pulling the cable. Any ideas on how these are serviced?

[bbc]

http://bicycletutor.com/guide/

Try this site, it may be of use (though I have never used it myself)

[subsea99]

Try this might not be same model but should give you an idea


Grip Shift SRT500 Service Instructions | Grip Shift | Retrobike
www.retrobike.co.uk/.../Grip+Shift/Grip+Shift+SRT5...
Grip Shift SRT500 Service Instructions. Date: 19/02/12. Owner: FluffyChicken. Size: 383x640, 1207x2019. Full size: 1207x2019 ...

[CaptainSlow]

ok thanks