Hi Pete, Problem as you have found is that the drive sprocket PR50-22A is behind the inner primary case T4/2. If you are very agile and flexible (and that is NOT me) you may be able to reach in to that area with a long flat blade screw driver to see if there is any discernible side to side wobble. Come to think of it, if you drained the fuel and oil , using suitable cushioning you could lay the bike on its side to make it a bit easier to gain access - I have NOT tried to do this - just a thought.Hi Martyn - I have gone through 2 Burman gearbox sprockets , just as you describe ( I have done 40,000 miles on the Comet) - both times have left me at opposite ends of the country (Ireland) .Fortunately it hasn't happened on any of our longer trips abroad! . Anyway, I am preparing the Comet for this years international , and I was wondering if there is any way to check the sprocket for "rocking" on the splines without having to strip out the primary side ? The most recent sprocket was a very tight fit , and has about 2,000 miles on it. I cant see any way to avoid taking the primary side off, but its worth asking.
I now carry as part of my standard touring spares a new drive sprocket and a new driving gear lock washer. In the interest of preventative maintenance I fit a brand new lock washer every time I replace the sprocket - cheap insurance.