Just aquired a sickly 2006 R III with the ground up gears due to the dislodged circlip issue. No worries though, it should be sorted in a couple of weeks. My first R III but far from my first Triumph. I have 4 in my stable at the moment ranging from this latest beast all the way back to a 1929 CN500.
This one has most definitely grond the 3/4 input gear along with the 4 output. I had it apart today and the circlip has jumped out and is all kinds of deformed and it was sat not where it was supposed to be.
This may clear up something. It would appear that the engine is a somewhat later replacement one than I was led to believe. Any idea of the approx date on this. Not gonna complain though. When I picked the bike up the motor was already out and strapped to a wheeled cart. After some contortions on my part I managed to snap a pic of what I believe is the engine number.