Oil Pump

CLEANING
1. Clean all parts thoroughly.

INSPECTION
1. Inspect mating surface of the chain case cover. Surface should be smooth. Replace cover if scratched or grooved.





Fig. 99

2. Lay a straightedge across the pump cover surface (Fig. 99). If a 0.025 mm (0.001 inch) feeler gauge can be inserted between cover and straight edge, cover should be replaced.





Fig. 100

3. Measure thickness and diameter of outer rotor. If outer rotor thickness measures 7.64 mm (0.301 inch) or less (Fig. 100), or if the diameter is 79.95 mm (3.148 inch) or less, replace outer rotor.





Fig. 101

4. If inner rotor measures 7.64 mm (0.301 inch) or less replace inner rotor (Fig. 101).





Fig. 102

5. Slide outer rotor into chain case cover, press to one side with fingers and measure clearance between rotor and chain case cover (Fig. 102). If measurement is 0.39 mm (0.015 inch) or more, replace chain case cover only if outer rotor is in specification.





Fig. 103

6. Install inner rotor into chain case cover. If clearance between inner and outer rotors (Fig. 103) is 0.203 mm (0.008 inch) or more, replace both rotors.





Fig. 104

7. Place a straightedge across the face of the chain case cover, between bolt holes. If a feeler gauge of 0.10 mm (0.004 inch) or more can be inserted between rotors and the straightedge, replace pump assembly (Fig. 104). ONLY if rotors are in specs.





Fig. 105

8. Inspect oil pressure relief valve and bore. Inspect for scoring, pitting and free valve operation in bore (Fig. 105). Small marks may be removed with 400-grit wet or dry sandpaper.
9. The relief valve spring has a free length of approximately 49.5 mm (1.95 inches) it should test between 19.5 and 20.5 pounds when compressed to 34 mm (1-11/32 inches). Replace spring that fails to meet specifications.
10. If oil pressure is low and pump is within specifications, inspect for worn engine bearings or other reasons for oil pressure loss.