INSPECTION

CYLINDER HEAD

Check the cylinder head gasket surface for flatness by using a straight edge and feeler gauge.

Standard value: 0.03 mm
Limit: 0.2 mm

If it exceeds the limit, correct to meet specification.

Grinding limit: *0.2 mm

* Includes combined with cylinder block grinding.

Cylinder head height (Specification when new): 120 mm

VALVE

Check the valve seat contact. Valve seat contact should be uniform at the center of the valve face. If incorrect, reface using a valve refacer.

If the margin is below the limit, replace the valve.

Standard value:

<Intake> 1.0 mm

<Exhaust> 1.2 mm

Minimum limit:

<Intake> 0.5 mm

<Exhaust> 1.0 mm

Measure the valve's total length. If the measurement is less than the limit, replace the valve.

Standard value:

<Intake> 111.33 mm

<Exhaust> 113.54 mm

Minimum limit:

<Intake> 110.83 mm

<Exhaust> 113.04 mm

VALVE SPRING

Measure the free height of the spring. If it is less than the limit, replace.

Standard value:

<Intake> 54.8 mm

<Exhaust> 56.1 mm

Minimum limit:

<Intake> 53.8 mm

<Exhaust> 55.1 mm

Measure the squareness of the spring. If it exceeds the limit, replace.

Standard value: 2 degrees or less
Limit: 4 degrees

VALVE GUIDE

Measure the clearance between the valve guide and valve stem. If it exceeds the limit, replace the valve guide or valve, or both.

Standard value:

<Intake> 0.02 - 0.04 mm

<Exhaust> 0.04 - 0.06 mm

Limit:

<Intake> 0.10 mm

<Exhaust> 0.15 mm

VALVE SEAT

Assemble the valve, then measure the valve stem projection between the end of the valve stem and the spring seating surface. If the measurement exceeds the specified limit, replace the valve seat.

Standard value:

<Intake> 48.33 mm

<Exhaust> 48.34 mm

Limit:

<Intake> 48.83 mm

<Exhaust> 48.84 mm

VALVE SEAT RECONDITIONING PROCEDURE

Before correcting the valve seat, check for clearance between the valve guide and valve and, if necessary, replace the valve guide.

Using the seat grinder, correct to obtain the specified seat width and angle.

After correcting the valve seat, lap the valve and valve seat using lapping compound. Then, check the valve stem projection.

VALVE SEAT REPLACEMENT PROCEDURE

Cut the valve seat from the inside to thin the wall thickness. Then, remove the valve seat.

Rebore the valve seat hole in the cylinder head to a selected oversize valve seat diameter.

Intake seat ring hole diameters

0.3 oversize: 35.30 - 35.33 mm

0.6 oversize: 35.60 - 35.63 mm

Exhaust seat ring hole diameters

0.3 oversize: 33.30 - 33.33 mm

0.6 oversize: 33.60 - 33.63 mm

Before fitting the valve seat, either heat the cylinder head up to approximately 250°C or cool the valve seat in liquid nitrogen, to prevent the cylinder head bore from galling.

Using a valve seat cutter, correct the valve seat to the specified width and angle.
See "VALVE SEAT RECONDITIONING PROCEDURE" on the previous page.

VALVE GUIDE REPLACEMENT PROCEDURE

Using a press, remove the valve guide toward the cylinder block.

CAUTION

Do not install a valve guide of the same size again.

Rebore the valve guide hole of the cylinder head so that it fits the press-fitted oversize valve guide.

Valve guide hole diameters

0.05 oversize 11.05 - 11.07 mm

0.25 oversize 11.25 - 11.27 mm

0.50 oversize 11.50 - 11.52 mm

Press-fit the valve guide until it protrudes 14.0 mm from the cylinder head top surface as shown in the illustration.

NOTE: When press-fitting the valve guide, work from the cylinder head top surface.

NOTE: Pay attention to the difference in length of the valve guides. (Intake side: 45.5 mm; exhaust side: 50.5 mm)

NOTE: After installing the valve guides, insert new valves in them to check for smooth operation.