How do you adjust valves on Onan engine model T260G?

To adjust the valves on an Onan T260G engine, first, ensure the engine is cool and disconnect the spark plug wires for safety. Remove the valve cover to access the rocker arms and valves. Using a feeler gauge, check the clearance between the rocker arm and the valve stem, and adjust it by loosening the lock nut and turning the adjustment screw until the correct clearance is achieved. Finally, reassemble the valve cover and reconnect the spark plug wires.