Checking The Camshaft Sprocket; Checking The Tappet Covers And Camshaft Sprocket Cover; Checking The Timing Chain Tensioner - Yamaha YFM70RY Service Manual

3. Measure:
• Cylinder head warpage
Out of specification → Resurface the cylinder
head.
Warpage limit
0.03 mm (0.0012 in)
M MMM M MMM M M MMM M
a. Place a straightedge "1" and a thickness
gauge "2" across the cylinder head.
1
b. Measure the warpage.
c. If the limit is exceeded, resurface the cylinder
head as follows.
d. Place a 400–600 grit wet sandpaper on the
surface plate and resurface the cylinder head
using a figure-eight sanding pattern.
TIP
To ensure an even surface, rotate the cylinder
head several times.
L LLL L LLL L L LLL L
EAS1S3L024

CHECKING THE CAMSHAFT SPROCKET

1. Check:
• Camshaft sprocket
More than 1/4 tooth wear "a" → Replace the
camshaft sprockets and the timing chain as a
set.
M MMM M M MMM M M MMM M
2
L LLL L L LLL L L LLL L
MMM
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
EAS23940
CHECKING THE TAPPET COVERS AND
CAMSHAFT SPROCKET COVER
The following procedure applies to both of the
tappet covers and O-rings.
1. Check:
• Tappet covers "1"
• Camshaft sprocket cover "2"
• O-ring
Damage/wear → Replace the defective
part(s).
EAS23960

CHECKING THE TIMING CHAIN TENSIONER

1. Check:
• Timing chain tensioner
Cracks/damage → Replace.
2. Check:
LLL
• One-way cam operation
Rough movement → Replace the timing
chain tensioner housing.
3. Check:
• Cap bolt
• Copper washer
• Spring
• One-way cam
• Timing chain tensioner gasket
5-10
CYLINDER HEAD
2 1