Checking The Camshaft Sprocket And Timing Chain Guide; Checking The Timing Chain Tensioner - Yamaha YZF-R125 Service Manual

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2. Check:
• Cylinder head
Damage/scratches → Replace.
• Cylinder head water jacket
Mineral deposits/rust → Eliminate.
3. Measure:
• Cylinder head warpage
Out of specification → Resurface the cylinder
head.
Warpage limit
0.03 mm (0.0012 in)
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a. Place a straightedge "1" and a thickness
gauge "2" across the cylinder head.
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.
NOTE:
To ensure an even surface, rotate the cylinder
head several times.
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EAS5D71031
CHECKING THE CAMSHAFT SPROCKET
AND TIMING CHAIN GUIDE
1. Check:
• Camshaft sprocket
More than 1/4 tooth wear "a" → Replace the
camshaft sprocket, timing chain and crank-
shaft as a set.
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
2. Check:
MMM
• Timing chain guide (exhaust side)
Damage/wear → Replace.
EAS24200

CHECKING THE TIMING CHAIN TENSIONER

1. Check:
• Timing chain tensioner
Cracks/damage/rough movement → Re-
place.
M MMM M MMM M
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.
LLL
b. Remove the screwdriver and slowly release
the timing chain tensioner rod.
5-10
CYLINDER HEAD
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1