2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 95Get this manual
Power unit 4Measure the valve guide inside diameterValve guide inside diameter: Intake and exhaust: 6.0006.018 mm (0.23620.2369 in)
2Install the new valve guide by striking the special tool from the camshaft side to the specified position a
Checking the valve seat
1Eliminate carbon deposits from the valve with scraper2Apply thin, even layer of Mechanic's blueing dye (Dykem) onto the valve seatNOTE: Before installing the valve guide, mark its installation position as shown Apply engine oil to the surface of the new valve guideValve guide removerinstaller: YM-04064-A Valve guide position a: 11.5 0.2 mm (0.45 0.01 in) 3Insert the special service tool into the valve guide 2, and then ream the valve guide4Measure the valve seat contact width where the blueing dye is adhered to the valve faceReface the valve seat if the valve is not seated properly or if the valve seat contact width is out of specificationReplace the valve guide if the valve seat contact is uneven3Lap the valve slowly on the valve seat with valve lapper (commercially available) as shown