Having fiddled a bit more and ridden up and down a bit, I've come to the conclusion the chain may be part of the issue, as the stickinging/slipping always seems to come in the same place/rhythm-so I wonder if a stiff part is the issue or a chain pin out of line that catches on the cage.. It's a Renolds 1/8th period chain, which I've always found to be quite a beefy chain, so I may try a modern 1/8th to see if that runs better.....
The flat coiled spring was good at grabbing mud and creating a grinding compound. I wonder if there is any wear inside the windings of the spring causing friction, or just enough to make it hessitate to accomodate the next cog - did that make any sense !?
I've remove it and cleaned it, and tried an alternative and both do the same so it's something in the set up somewhere rather than the parts per say I think, unless it's the chain that is
Having fiddled a bit more and ridden up and down a bit, I've come to the conclusion the chain may be part of the issue, as the stickinging/slipping always seems to come in the same place/rhythm-so I wonder if a stiff part is the issue or a chain pin out of line that catches on the cage.. It's a Renolds 1/8th period chain, which I've always found to be quite a beefy chain, so I may try a modern 1/8th to see if that runs better.....