Re-Fitted my old sprocket this morning as there was little to no wear detectable, The new one I purchased (Renthal) was 15 tooth, and the one that was on the bike was a 16, so, I have ordered another new 16 tooth Renthal.
I will leave the original one on for a few more thousand miles before changing it as it is still in good nick.
I put a new 12 mm nut on with a new Tab Washer to the recommended torque of 90Nm and used Loctie 620 thread lock and bent the tabs over two of the nut flats.
Chain was thoroughly cleaned with Motol Chain cleaner and a rotory chain cleaning brush, dried and lube up liberally with Motol Chain Lube, adjusted chain at the tightest part on the lower run so that the chain just touched the rubber chain guide when pushed up about 40mm of play.
Went for a run this afternoon down to Loomies bikers cafe in Hampshire ended up chatting with really interesting guy who raced Lambretta Scooters years ago. Drank a huge mug of tea and woofed back a basket full of cheesy chips drenched in sweet chilli sauce. There must have been about 120 bikes there, lovely sunny afternoon but a bit nippy on the old fingers.
Fast ride home, bike on the patio washed and dried off, re-checked the chain adjustment, all OK. Photo of the bike taken and back in its home.