Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 278Get this manual

CAMSHAFT AND VALVES (4)Bore the valve guide using the valve guide reamerValve guide reamer: NA90890-06804

When installing and removing the valve guide reamer, apply machining oil and turn the reamer clockwise

REFACING THE VALVE SEAT NOTE:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives