Yamaha Marine Outboards F4A/F4 Factory Service Manual, Page 166Get this manual
ROCKER ARM AND VALVES
8 Apply the fine lapping compound to the valve face and repeat the above stepsNOTE:
Be sure to clean off all compound to the valve face and valve seat after every lapping operation8 Apply the Mechanic's bluing dye to the valve face8 Install the valve into the cylinder head8 Press the valve through the valve guide and onto the valve seat to mark clear pattern8 Measure the valve seat width againIf the valve seat width is out of specification, reface and lap the valve seatValve installation 1Install: 9Valve 9Valve spring 9Spring retainer 9Valve cotter Valve spring compressor: YM-0125390890-04019 Attachment: YM-0411490890-04018