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)
![](https://motoinstruction.ru/img/yamaha/3/111831.jpg)
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».
![](https://motoinstruction.ru/img/yamaha/3/111832.jpg)
b. Install the new valve guide with the valve guide installer «2» and valve guide remover
![](https://motoinstruction.ru/img/yamaha/3/111833.jpg)
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.
![](https://motoinstruction.ru/img/yamaha/3/111834.jpg)
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)
![](https://motoinstruction.ru/img/yamaha/3/111835.jpg)
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).
![](https://motoinstruction.ru/img/yamaha/3/111836.jpg)