90031-PNA-004 Honda BOLT-WASHER (10X30) (Honda Code 6752398).

Measurement of Distortion of Cylinder Head Bottom Surface
Place a straight edge on the bottom surface of the cylinder head, measure the amount of surface distortion using feeler gages, and, if the limit value is exceeded, reface the surface with a surface grinder.
Measurement of distortion of cylinder head bottom surfaceMeasurement of Rocker Arm Inside Diameter and Rocker Shaft Diameter
Measure the inside diameter of the rocker arm (bushing) and the diameter of the rocker shaft to calculate the clearance between the rocker arm and shaft, and replace the rocker arm if the clearance is within the limit value. If the limit value is exceeded, replace the rocker arm and shaft.
Measurement of rocker arm inside diameter and rocker shaft diameterMeasurement of Valve Spring Perpendicularity and Free Length
Inspect each valve spring for perpendicularity and free length, and, if the limit value is exceeded, replace the valve.
Measurement of valve spring perpendicularity and free lengthMeasurement of Pushrod Runout
If the pushrod runout exceeds the standard value, replace the pushrod. The standard value above is based on dial gage reading.
Measurement of pushrod runoutMeasurement of Valve Stem Diameter
If the stem diameter exceeds the limit value, replace the valve stem. Also replace the valve stem if it is unevenly worn.
Measurement of valve stem diameterMeasurement of Clearance Between Valve Stem and Valve Guide
Measure the valve guide bore with and internal bore micrometer.Because the valve guide wears more rapidly at the upper and lower ends, measure the diameter at both ends in two crossing directions. If the limit is exceeded, replace worn parts. Remove carbon deposits from the valve and valve guide before measuring the clearance.
Measurement of valve guide inside diameter
Removal of valve guideReplacement of Valve Guides
(1) To remove the valve guides, use the valve guide remover.(2) To press-fit the valve guides, use the valve guide installer and a press.
Be sure to use the valve guide installer in order to drive the valve guide to the prescribed depth.
(3) After installing the valve guide, insert a new valve and check the smoothness of the movement.(4) When the valve guide is replaced, check the contact of the valve with the valve seat.
Installation of valve guideInspection of Valve Faces
Coat the valve face lightly with shinmeitan, and use the valve lapper to inspect the valve contact with the valve seat. If the contact is not uniform and the valve is defective, or if a limit is exceeded, correct or replace the valve and valve seat.
Inspection of valve face (a) Inspect the valve face after the valve guide is inspected or replaced.(b) When pressing the valve coated with shinmeitan against the valve seat, do not rotate the valve.(c) After the valve or valve seat is corrected or replaced, lap the valve against the valve seat.
Valve seat contact with seat
Valve contact with seatReplacement of Valve Seats
(1) Removal of valve seatWeld a stud or bar to the valve seat, insert a shaft into the valve guide bore from the top of the cylinder head, and drive the seat off the cylinder head. When welding the stud, do not allow spatter to adhere on the machined surfaces of the cylinder.
Removal of valve seat(2) Installation of valve seat(a) Before inserting a new valve seat, measure the cylinder head bore to which the valve seat is installed to make sure the dimension conforms to the standard.
Valve seat installation dimension(b) When installing a valve seat, keep the cylinder head at room temperature and cool the valve seat in liquid nitrogen (approx. -170 °C [-274 °F]) for more than 4 minutes, or heat the cylinder head to 80 to 100 °C [176 to 212 °F] and keep the valve seat chilled in ether or alcohol containing dry ice.(c) Using the insertion/caulking tool, drive the valve seat into place.
Installation of valve seatRefacing Valve Faces
If the valve face is excessively worn, reface it with a valve refacer. (a) Reface the valve face to an angle of 30°.(b) Be sure to ensure the valve margin limit. If the grinding does not result in the conformity of the dimension, replace the valve.
Refacing valve faceRegrinding Valve Seats
Use the valve seat cutter or valve seat grinder to reface the valve seat. After refacing, grind the seat lightly by inserting #400-grade sandpaper between the cutter and valve seat. (a) Grind the valve seat as little as possible.(b) If the seat width exceeds the limit due to wear or as a result of grinding, replace the valve seat.
Regrinding valve seatLapping Valves Against Valve Seats
Be sure to lap each valve in its valve seat after the valve or seat has been refaced or replaced.(1) Coat the seat contact surface of the valve face lightly and evenly with a lapping compound. (a) Do not allow the compound to adhere on the valve steam.(b) Use a compound of medium coarseness (120 to 150 mesh) for initial lapping, and use a finer compound (200 mesh or finer) for finishing.(c) Mix a small amount of engine oil with the compound for smooth and even application.(2) Use the valve lapper to lap the valve in the seat. To lap, strike the valve against the vale seat while rotating the valve a little at a time.(3) Wash off the compound with diesel fuel.(4) Coat the seat contact surface of the valve face with engine oil, then lap the valve again.(5) Inspect the valve face for contact.
Lapping valve against valve seatReplacement of Combustion Jets
Replace the combustion jets only when cracks or other abnormal conditions are found.(1) To remove the combustion jet, insert a round rod measuring about 6 mm [0.24 in] in diameter into the glow plug mounting hole, and lightly tap the inside surface of the je