2009 Yamaha F40 Outboard Service Manual, Page 221Get this manual
Power unit Cam lobe height a: Intake: 30.73730.837 mm (1.21011.2141 in) Exhaust: 30.93331.033 mm (1.21781.2218 in) Cam lobe width b: 25.95026.050 mm (1.02171.0256 in) 2Measure the camshaft runoutReplace if above specification
Valve lapper a: (commercially available) 8Check the valve seat contact area againSee "Checking the valve seat" (7-38)
Checking the rocker arm and rocker arm shaft
1Check the rocker arms, the rocker arm shaft, and the contact surface of each rocker armReplace if worn2Measure the rocker arm inside diameter and the rocker arm shaft outside diameter cReplace if out of specification