2004-2005 660 Yamaha Rhino Factory Service Manual, Page 157Get this manual
VALVES AND VALVE SPRINGS
3Check: valve face Pittingwear Grind the face valve stem end Mushroom shape or diameter larger than the body of the stem Replace
VALVES AND VALVE SPRINGS
3Check: valve face Pittingwear Grind the face valve stem end Mushroom shape or diameter larger than the body of the stem Replace