OK so mystery solved, I think. I fitted my new chain and sprockets today and upon inspection of the old chain it seems that I tightened one of the rivets on the master link too tight as it was very stiff. I am assuming that this is what caused the premature wear on the Renthal sprockets. I checked and double checked the master link on the new chain after riveting and it seems as flexible as the others so hopefully I will not get the same problem again. If I do it will be endless chains for me from now on even if it does mean I have to remove the swingarm to fit them! It was my first time riveting a chain however and I feel confident that I have done it properly this time so I doubt I will have to resort to that.

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Now have a 2017 S1000XR Sport SE

2006 XT660X - Cat D write off due to someone pulling out on me - Pipewerx carbon fibre exhausts - Snorkel removed and airbox drilled - DNA stage 1 + 2 air filters - Kevs fuel controller mod - Scottoiler V system - Oxford heated grips - HEL braided brake hoses - Wilbers 540 rear shock - Brembo brake pads - AFAM chain and sprockets - Michelin Pilot Street Radial's - Denali DX Xtreme dual intensity spotlights