Hi having had the bike stop pulling me up hills I took it apart and found the small cog with a horse shoe clip holding it in place when removed and cleaned has safty system not seen till removed the round spindle that goes through the middle of the cog has 2 flat sides and the cog has what looks like the letter H in the top the 2 downrights of the H hold a rubber and a metal shim thin strip that on my bike had broken and so dint grip the spindle causing loss of power under strain but enough when on the flat. I do have pics but can't work out how to uploa. As part of the reccomended regreas each year you are next to this cog so well worth a check my brother is making new shims for me as there not of the shelf items as they are about 5x10mm rectangle as thick as a sowing needl. I have collected lots of pics to help do the service and hope to put them on here when I can
Hope this helps
From Paul
Hope this helps
From Paul