Inspection And Repairing

Cylinder Head

1 Remove the intake and exhaust tappet covers

2 Insert a 6 mm (0.24 in) screw into the rocker shaft, and withdraw the rocker shaft It should be slide out easily

If does not slide out easily, use the special tool as shown.

and the lubrication system (pump and passages)checked

Standard shaft diameter: 1 1 975 ~ 11.990 mm (0 471 — 0 472 in)

3. Rocker arm and rocker shaft a. The rocker arm usually wears at two locations (1) at the rocker shaft hole. (2) at the cam lobe contacting surface, b Measure the rocker arm inside diameter.

Standard size

c The shaft has been hardened and it should not wear excessively If a groove has developed in this surface that can be felt, or if it shows a blue discoloration. then the shaft should be replaced d Standard clearance between the rocker shaft and hole should be 0.010 — 0 043 mm (0 0004 - 0.0017 in). If measurement shows more than 0.1 mm clearance, replace either or both parts as necessary.

4. Compress the valve spring and then remove both retainer locks Remove the compressor and lift off the retainer and springs

The retainer locks might be partially stuck in the retainer Use a rubber hammer to tap the edge of the retainer a few times to loosen the retainer locks

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Intake valve stem diameter 6 975 — 6 990 mm (0 2746- 0 2752 in) Exhaust valve stem diameter: 6 955- 6 970 mm (0 2529- 0 2744 in)

2 Checking the valve springs a This engine use two springs of different si2es to prevent valve float or surging The chart below shows the basic value characteristics b Even though the spring is constructed of durable spring steel, it gradually loses some of its tension This is evidenced one way by a gradual shortening of free length. Use a vernier caliper to measure spring free length If the free length of any spring has decreased more than 2 mm (008 in) from its specification, replace it

6 Decarbonization of the head and components

Carbon deposits build up in the combustion chambers, on the valves, and in the exhaust ports Thoroughly clean all parts with a blunt scraper, then wash in solvent and dry with compressed air The parts can then be examined and measured for wear.

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5 Pull the valve out. If the stem tip or retainer lock groove edges are slightly expanded. causing difficult removal, the surface might be damaged First, use a fine file to remove any lip that exists on the stem and then remove the valve

Be sure to remove the valve stem seal before removing the valve. Otherwise the seal could be damaged

Valves. Valve Springs. Valve Guides and Valve Seats

1 Check the intake and exhaust valve stems for bending and grooved wear. And check the stem ends for wear Measurements should be done in three positions, upper, middle, and lower.

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