It unscrews in the conventional manner (IE it's a right hand thread).
There IS a special socket that fits over the whole assy, but you can make do ;-
1) Re-install the 2 screws that hold the wire screen in place. This will prevent the assembly from falling apart.
2) Using a drift on the screw lugs, 'knock' it round with a hammer.
phil_saunders@bigfoot.com
Phil Saunders
August 2008