I love my 2009 Belagio (30000 miles) but am increasingly frustrated by the slop in the drivetrain. Accelerating through corners is not smooth. If this were a Tonti, I’d replace the cush drive and reshim the bevel box. but how do i get rid of the slack in a CARC?
Might be stupid question, but how many revs are you doing round these corners and what gear?
It could be the rubber bush in the torque arm if it has been upgraded from the ball joint type.
i realise I’m late to the party, but . . .
Are you sure it’s freeplay/backlash in the Drive?
Too much slack in the Throttle Cables can give very similar symptoms if you’re just off idle.
Get the rear Wheel off the Ground, stick it in gear, and try and rotate the Wheel in both directions, see how much actual movement you get.
Try it in all the Gears.
Sorry very late to the party, I am on my second Bellagio both 2009 models and they are both like that, horrendous backlash in the drive train, very clunky gearbox at low revs but really nice gear change when you are getting a move on, the worst bit is navigating tight mountain roads when you start opening the throttle at the apex of a corner when the drivetrain catches up, it’s the worst part of the bike. You can remove all the slack from the throttle cables and it won’t make any difference. Filling the gearbox with heavy grease may help 
(don’t)