1. Eliminate: combustion chamber carbon deposits (with a rounded scraper)
![](https://motoinstruction.ru/img/yamaha/16/122266.jpg)
Note: Do not use a sharp instrument to avoid damaging or scratching:
- spark plug threads
- valve seats
2. Check: cylinder head
Damage/scratches → Replace.
3. Measure: cylinder head warpage
Out of specification → Resurface the cylinder head.
- Cylinder head warpage: Less than 0.03 mm
a. Place a straightedge (1) and a thickness gauge (2) across the cylinder head.
![](https://motoinstruction.ru/img/yamaha/16/122267.jpg)
b. Measure the warpage.
c. If the limited is exceeded, resurface the cylinder head as follows.
d. Place 400 - 600 grit wet sandpaper on the surface plate and resurface the cylinder head using a figure-eight sanding pattern.
Note: To ensure an even surface, rotate the cylinder head several times.