Almost all cat clutch bolts use a 1/2" (or 13mm) 12 point socket.
They also use the same clutch puller from the mid 90's to 2009.
The exception to this rule is the 1000 twin and Z 1 four stroke engine, these use a large torx bit to remove the clutch bolt, and a clutch puller with metric thread (if you buy a puller from arctic cat it will be painted orange)
All 2010 machines require a metric clutch puller, from arctic cat is green. This new puller will work with the 1000 twin and Z1, but the orange puller will not work with the 2010 clutches.
I would remove the diamond drive, take it apart, clean it out, inspect the gears and bearings, and change the seals.