for those of us with 05 bikes (not sure about other years), especially if you have the Bandit clutch, you need to do this to a) correct the alignment between the motor sprocket and clutch pack, and b) to help the scraping of the clutch housing against the inner primary - remember Jakes thread. Here is a pic of the misalignment without the shim. It looks in the pic like the straight edge is against the inner hub - it isn't. Here is a pic of the shim and the shim in place. You can also see the scrape marks in the second pic. Here is what the alignment looks like after the shim is in place - still not perfect but better. I should have stuck a feeler gauge in there to measure it but forgot. I also used the tool I made by bolting together a friction plate and a steel plate - worked a charm and Al, left no marks on the hubs at all. and here is the fluids I'm now using - I thought it was about time we had another oil thread! I also pulled the stator off and it was full of tiny shavings - see Jakes pic - it was exactly the same and that is a bastard to clean because, of course, its magnetic.