The 'clutch' - if we want to dignify it with such a description - is simply a belt/pulley arrangement that releases tension on the drive belt when activated. The belt tension is set by a spring, and is therefore not adjustable. If yours is slipping, the transmission drive belt must be extremely worn, and you need a new drive belt. You will need to remove the cutter deck to change it.
phil_saunders@bigfoot.com
Phil Saunders, June 2008