Checking The Timing Chain And Camshaft Sprocket; Checking The Timing Chain Tensioners - Yamaha WR250R Service Manual

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5. Measure:
Camshaft journal diameter "a"
G
Out of specification → Replace the camshaft.
Within specification → Replace the cylinder
head and the camshaft caps as a set.
Camshaft journal diameter
21.959–21.972 mm (0.864–0.865
in)
EAS23870
CHECKING THE TIMING CHAIN AND
CAMSHAFT SPROCKET
1. Check:
Timing chain "1"
G
Damage/stiffness → Replace the timing
chain and camshaft and camshaft sprocket
as a set.
2. Check:
Camshaft sprocket
G
More than 1/4 tooth wear "a" → Replace the
camshaft sprocket and the timing chain as a
set.
1
5-10
a
b
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
EAS23960
CHECKING THE TIMING CHAIN
TENSIONERS
The following procedure applies to both of the
timing chain tensioners.
1. Check:
Timing chain tensioner
G
Cracks/damage → Replace.
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
a. Using a finger, push and insert timing chain
tensioner rod "1" into the timing chain
tensioner housing.
NOTE:
Push the timing chain tensioner rod in direction
"a", and turn the timing chain tensioner body "2"
in direction "b" until it stops.
b
b. Keep pressing the timing chain tensioner rod,
mount clip "3" into groove "4", and lock the
timing chain tensioner rod.
c. Push the timing chain tensioner rod in direc-
tion "c".
d. Make sure that the timing chain tensioner rod
can smoothly move out from the timing chain
tensioner housing in direction "d". If not
smooth, replace the timing chain tensioner
assembly.
CAMSHAFT
1
2
2
a
1