1. Measure:
- Valve-stem-to-valve-guide clearance. Out of specification → Replace the valve guide.
Valve-stem-to-valve-guide clearance = Valve guide inside diameter «a» - Valve stem diameter «b».
Valve-stem-to-valve-guide clearance
- Intake: 0.010–0.037 mm (0.0004–0.0015)
- Limit: 0.08 mm (0.0032 in)
- Exhaust: 0.025–0.052 mm (0.0010–0.0020 in)
- Limit: 0.10 mm (0.0039 in)
2. Replace:
- Valve guide
Note: To ease valve guide removal and installation, and to maintain the correct fit, heat the cylinder head to 100°C (212°F) in an oven.
a. Remove the valve guide with the valve guide remover «1».
b. Install the new valve guide with the valve guide installer «2» and valve guide remover
c. After installing the valve guide, bore the valve guide with the valve guide reamer «3» to obtain the proper valve-stem-to-valve-guide clearance.
Note: After replacing the valve guide, reface the valve seat.
Intake: Valve guide remover (∅4): 90890-04111 YM-04111
Exhaust: Valve guide remover (∅4.5): 90890-04116 YM-04116
Intake: Valve guide installer (∅4): 90890-04112 YM-04112
Exhaust: Valve guide installer (∅4.5): 90890-04117 YM-04117
Intake: Valve guide reamer (∅4): 90890-04113 YM-04113
Exhaust: Valve guide reamer (∅4.5): 90890-04118 YM-04118
3. Eliminate:
- Carbon deposits
4. Check:
- Valve face. Pitting/wear → Grind the valve face.
- Valve stem end. Mushroom shape or diameter larger than the body of the valve stem → Replace the valve.
5. Measure:
- Valve margin thickness «a»
Out of specification → Replace the valve.
Valve margin thickness: 0.5-0.9 mm (0.0197-0.0354 in)
Limit: 0.5 mm (0.02 in)
6. Measure:
- Valve stem runout
Out of specification → Replace the valve.
Notes:
- When installing a new valve, always replace the valve guide.
- If the valve is removed or replaced, always replace the oil seal.
Valve stem runout: 0.010 mm (0.0004 in).
