Checking The Timing Chain Guides; Checking The Timing Chain Tensioners - Yamaha YFM250RX 2008 Service Manual

CYLINDER HEAD

CHECKING THE TIMING CHAIN GUIDES

The following procedure applies to the cam-
shaft sprockets and timing chain guides.
1. Check:
• Timing chain
Damage/stiffness → Replace the timing
chain and camshaft sprocket and crank-
shaft sprocket as a set.
2. Check:
• Camshaft sprocket
More than 1/4 tooth wear
the timing chain and camshaft sprocket and
crankshaft sprocket as a set.
1/4 tooth
Correct
Timing chain
Camshaft sprocket
3. Check:
• Timing chain guide (exhaust side)
CHECKING THE TIMING CHAIN
TENSIONERS
1. Check:
• Timing chain tensioner
Cracks/damage → Replace.
2. Check:
• One-way cam operation
Rough movement → Replace the timing
chain tensioner housing.
a. Lightly press the timing chain tensioner rod
into the timing chain tensioner housing by
hand.
NOTE: NOTE:
While pressing the timing chain tensioner rod,
wind it clockwise with a thin screwdriver
until it stops.
4-11
ENG
→ Replace