Checking The Timing Chain And Camshaft Sprocket; Checking The Timing Chain Guides; Checking The Timing Chain Tensioner - Yamaha MTN850-A 2017 Service Manual

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5. Measure:
• Camshaft journal diameter "a"
Out of specification  Replace the camshaft.
Within specification  Replace the cylinder
head and the camshaft caps as a set.
Camshaft journal diameter
24.459–24.472 mm (0.9630–
0.9635 in)
EAS30258
CHECKING THE TIMING CHAIN AND
CAMSHAFT SPROCKET
1. Check:
• Timing chain
Damage/stiffness  Replace the timing
chain and camshaft and camshaft sprocket
as a set.
2. Check:
• Camshaft sprocket
More than 1/4 tooth wear "a"  Replace the
camshaft sprockets and the timing chain as a
set.
a. 1/4 tooth
b. Correct
1. Timing chain
2. Camshaft sprocket
EAS30265

CHECKING THE TIMING CHAIN GUIDES

The following procedure applies to all of the
camshaft sprockets and timing chain guides.
1. Check:
• Timing chain guide (intake side) "1"
• Timing chain guide (top side) "2"
Damage/wear  Replace the defective
part(s).
EAS30266

CHECKING THE TIMING CHAIN TENSIONER

1. Check:
• Timing chain tensioner
Cracks/damage/rough movement  Re-
place.
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a. Lightly press the timing chain tensioner rod
into the timing chain tensioner housing by
hand.
TIP
While pressing the timing chain tensioner rod,
wind it counterclockwise with a hexagon wrench
"1" (Parts No.: 1RC-12228-00) until it stops.
5-13
CAMSHAFTS
2
1