Yamaha YFM45FAR, Service Manual

Page: 150 / 405

4 - 12
ENG
CYLINDER HEAD
CHECKING THE CYLINDER HEAD
1.Eliminate:
●
Carbon deposits (from the combustion
chambers)
Use a rounded scraper.
NOTE:
Do not use a sharp instrument to avoid
damaging or scratching:
●
Spark plug threads
●
Valve seats
2.Check:
●
Cylinder head
Scratches/damage
→
Replace.
●
Cylinder head water jacket
Mineral deposits/rust
→
Eliminate.
3.Measure:
●
Cylinder head warpage
Out of specification
→
Resurface.
*****************************************************
Measurement and resurfacing steps:
●
Place a straightedge and a feeler gauge
across the cylinder head.
●
Use a feeler gauge to measure the warpage.
●
If the warpage is out of specification,
resurface the cylinder head.
●
Place a 400 ~ 600 grit wet sandpaper on the
surface plate, and resurface the head using
a figure-eight sanding pattern.
NOTE:
To ensure an even surface rotate the cylinder
head several times.
*****************************************************
Cylinder head warpage:
Less than 0.03 mm (0.0012 in)