The Sturmey Archer trigger shifter that I originally bought for Charles had served me well, although recently it had started to slip from the lowest gear occasionally, the trigger feel started to feel a little loose as well and I came to the conclusion that it needed an overhaul. The feel of the trigger is mostly governed by the spring tension of the pawl that holds the gear in place, this needed to be re-tensioned to restore it's feel.
The construction of the trigger shifter consists of a ratchet and pawl type mechanism sandwiched in a housing, the mechanism pivots on two rivets. To access the insides I would have to remove the rivets by drilling out the small end and then punching them out.
It was as easy as pulling the spring back to increase the tension.
The ratchet mechanism came out and I cleaned and greased it, the internal parts looked like they were in good condition as they were made of hardened steel. The rivets were replaced with M3 x 20mm screws which fit perfectly after drilling out the body.
With the spring tension restored the gear clicks were now a lot louder and more positive, the trigger once again had a springy return. These trigger shifters aren't meant to be serviceable however it's quite easy to do so if you have the right tools. Thanks for reading.