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 clear-ance.
Valve-stem-to-valve-guide clearance (intake) 0.010-0.037 mm (0.0004-0.0015 in).
Limit 0.080 mm (0.0032 in).
Valve-stem-to-valve-guide clearance (exhaust) 0.025-0.052 mm (0.0010-0.0020 in).
Limit 0.100 mm (0.0039 in).
![](https://motoinstruction.ru/img/yamaha/20/126641.jpg)
2. Replace:
- Valve guide
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/20/126642.jpg)
b. Install the new valve guide with the valve guide installer "2" and valve guide remover "1".
![](https://motoinstruction.ru/img/yamaha/20/126643.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/20/126644.jpg)
After replacing the valve guide, reface the valve seat.
Valve guide remover (04.5) 90890-04116.
Valve guide remover (4.5 mm) YM-04116.
Valve guide remover (05) 90890-04097.
Valve guide remover (5.0 mm) YM-04097.
Valve guide installer (04.5) 90890-04117.
Valve guide installer (4.5 mm) YM-04117.
Valve guide installer (05) 90890-04098.
Valve guide installer (5.0 mm) YM-04098.
Valve guide reamer (04.5) 90890-04118.
Valve guide reamer (4.5 mm) YM-04118.
Valve guide reamer (05) 90890-04099.
Valve guide reamer (5.0 mm) YM-04099.
3. Eliminate:
- Carbon deposits (from the valve face and valve seat)
4. Check:
- Valveface
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. Valve margin thickness D (intake) 1.35-1.75 mm (0.0532-0.0689 in). Valve margin thickness D (exhaust) 0.50-0.90 mm (0.0197-0.0354 in).
![](https://motoinstruction.ru/img/yamaha/20/126645.jpg)
6. Measure:
- Valve stem runout
Out of specification → Replace the valve.
- When installing a new valve, always replace the valve guide.
- If the valve is removed or replaced, always replace the oil sea.
Valve stem runout 0.010 mm (0.0004 in).
![](https://motoinstruction.ru/img/yamaha/20/126646.jpg)