How do you Adjust valves Briggs 16 HP Briggs and stratton in a craftsman 1000 series riding mower?

If its a OHV(Over Head Valve) motor, you can, if not, you cant. If it is a OHV engine, you have to use a five thousands feeler gauge, and adjust the nuts on top of the valves to tighten or loosen the clearance between the valve and the rocker arm, also to do this you must make sure that the motor is a TDC on the beginning of the Power stroke. Then slide the feeler gauge in between the rocker arm and the valve until you can barely slide the feeler gauge in between them. then tighten down the lock nut on the adjusting nut and put the valve cover back on.