2003 Polaris ATV Trail Boss 330 Factory Service Manual, Page 66Get this manual
ENGINE NOTE: When using an interference angle, the seat contact point on the valve will be very narrow, and is normal conditionLook for an even and continuous contact point on the black marker, all the way around the valve face12Clean cylinder head, valves, and camshaft oil supply passage (A) thoroughly
Seat Width
Valve Seat Width: Intake Std: .039I (1.0 mm) Limit: .055I (1.4 mm) Exhaust Std: .059I (1.4 mm) Limit: .071I (1.8 mm) 13Spray electrical contact cleaner into oil passage and dry using compressed air
CYLINDER HEAD ASSEMBLY