Yamaha YFM660FS, Supplementary Service Manual

Page: 233 / 478

4 - 20
ENG
CAMSHAFT AND CYLINDER HEAD
CHECKING THE TIMING CHAIN GUIDE
1.Check:
●
Exhaust side timing chain guide
Wear/damage
→
Replace.
CHECKING THE TIMING CHAIN
TENSIONER
1.Check:
●
Timing chain tensioner
Cracks/damage/rough movement
→
Replace.
*****************************************************
a.Lightly press the timing chain tensioner rod
into the timing chain tensioner housing by
hand.
NOTE:
While pressing the timing chain tensioner rod,
wind it clockwise with a thin screwdriver
1
until it stops.
b.Removing the screwdriver and slowly
release the timing chain tensioner rod.
c.Make sure that the timing chain tensioner rod
comes out of the timing chain tensioner
housing smoothly. If there is rough move-
ment, replace the timing chain tensioner.
*****************************************************
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 damag-
ing or scratching:
●
Spark plug threads
●
Valve seats
2.Check:
●
Cylinder head
Scratches/damage
→
Replace the cylinder
head cover and cylinder head as a set.
●
Cylinder head water jacket
Mineral deposits/rust
→
Eliminate.