Depends on the model. Assuming vertical crank - remove any plastic covers/cowls if any. Some unbolt, some unclip. The bolts/screws are not hidden - if you cant find any, chances are you can gently lever it off. The recoil assembly will either be attached by 2 or 3 small self tappers, or it will simply be bolted to the top of the engine with 4 bolts. If there doesn't seem to be any way of detatching the recoil, you will have to remove the cowling. Remove fuel tank, Unbolt dipstick tube if fitted. Remove 4 bolts securing cowling to gain access to recoil pulley. Horizontal crank engines will be similar.
Phil Saunders, November 2007