1996-2005 Suzuki DF40, DF50 Four Stroke Outboard Service Manual, Page 34Get this manual
PERIODIC MAINTENANCE 2-8
TAPPET CLEARANCE
Inspect initially after 20 hours (1 month) and every 200 hours (12 months) thereafter The tappet clearance specification is the same for both intake and exhaust valvesToo small tappet clearance may reduce engine power, too large tappet clearance increases valve noise and hastens valve and seat wearWhen the tappets are set to the specified clearance, the engine will run without excessive noise from the valve mechanism and will deliver full powerIn this engine, the tappet clearance is increased or decreased by replacing the shim disc, made of special wear resistant material, fitted to the top of the tappetThe shim discs are easy to remove and refitTappet clearance adjustment must be checked and adjusted: at the time of periodic inspection when the valve mechanism is serviced when the camshafts are disturbed by removing them for inspection