Valve Seat Reconditioning: Reconditioning

How to use this Service Information .

1. Valve Seat - Reconditioning

   ■ Preconditions 

   • Valve Removed
   • Valve Stem-to-Guide Clearance Normal Condition 

   Figure 1 

   Courtesy of HONDA, U.S.A., INC.

   ■ Procedure/Specifications 

   1. Renew the valve seats in the cylinder head using a valve seat cutter. (Figure 1)2. Carefully cut a 45° seat, removing only enough material to ensure a smooth and concentric seat.

   Figure 2 

   Courtesy of HONDA, U.S.A., INC.

   3. Bevel the upper and lower edges at the angles shown. Check the width of the seat and adjust accordingly.

   Valve Seat Angle (Figure 2) 

   Position	Intake	Exhaust
   A	21 deg.	26.5 deg.
   B	45 deg.	45 deg.
   C	65 deg.	60 deg.

   4. Make one more very light passes with the 45° cutter to remove any possible burrs caused by the other cutters.

   Valve Seat Width 

   Specifications
   Standard (New)	Intake	1.25-1.55 mm (0.0492-0.0610 in)
   	Exhaust	1.45-1.75 mm (0.0571-0.0689 in)
   Service Limit	Intake	1.90 mm (0.0748 in)
   	Exhaust	2.22 mm (0.0874 in)

   Figure 3 

   Courtesy of HONDA, U.S.A., INC.

   5. After resurfacing the seat, inspect for even valve seating: Apply Prussian Blue compound (D) to the valve face. Insert the valve in its original location in the head, then lift it and snap it closed against the seat several times. (Figure 3)

   6. The actual valve seating surface (E), as shown by the blue compound, should be centered on the seat (Figure 3):

   • If it is too high (closer to the valve stem), you must make a second cut with the 65° cutter (intake seat) or 60° cutter (exhaust seat) to move it down, then one more cut with the 45° cutter to restore seat width.
   • If it is too low (close to the valve edge), you must make a second cut with the 21° cutter (intake seat) or 26.5° cutter (exhaust seat) to move it up, then make one more cut with the 45° cutter to restore seat width.
     NOTE: The final cut should always be made with the 45° cutter.

   Figure 4 

   Courtesy of HONDA, U.S.A., INC.

   7. Insert the intake and exhaust valves in the cylinder head, and measure the valve stem installed height (F). (Figure 4)

   Intake Valve Stem Installed Height 

   Specifications
   Standard (New)	52.75-53.65 mm (2.0768-2.1122 in)

   Specifications
   Service Limit:	53.75 mm (2.1161 in)

   Exhaust Valve Stem Installed Height 

   Specifications
   Standard (New)	50.40-51.30 mm (1.9842-2.0197 in)
   Service Limit:	51.40 mm (2.0236 in)

   8. If the valve stem installed height is over the service limit, replace the valve and recheck. If it is still over the service limit, replace the cylinder head; the valve seat in the head is too deep.