Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 270Get this manual
CAMSHAFT AND VALVES REMOVING THE VALVE
Remove: Valve spring lock Valve spring retainer Valve spring Valve spring seat Intake valve or exhaust valve Valve spring compressor: YM-0125390890-04019 Attachment: YM-0401890890-04018
Set the attachment on to the center of the spring retainerDo not overtighten the valve spring compressor
CHECKING THE VALVE AND VALVE GUIDE
1Measure: Valve guide inside diameter Out of specification Replace