Taz - When I de-restricted my lads Scooter, I had the same problem getting the variator nut off
His was a Yamaha Aerox (Same as MBK Nitro) which uses Italian Minnarelli engine
I balanced a flat bladed screwdriver on a block of wood so the castlelated (?) nut didn't move, getting my son to hold the screwdriver
Then with the correct socket on a sliding T bar, wacked the sliding T bar with a hammer & hey presto the nut came loose
Then it was easy to remove all the variator shite !
Even changed the clutch rollers to speed up acceleration
Refitting is a reversal of removing !
Bit 'heath robinson' I know, but it worked & I didn't even round the nut off
Fookin' thing used to go off the clock, over 60 mph even with my stealth like figure on it !