Yamaha MX775 - Page 42

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ENGINE
ENGINE INSPECTION
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a. If the compression pressure is below the minimum
specification, pour a teaspoonful of engine oil into
the spark plug hole and measure again. Refer to
the following table.
b. If the compression pressure is above the maximum
specification, check the cylinder head, valve sur-
faces and piston crown for carbon deposits.
Carbon deposits  Eliminate.
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5. Install:
• Spark plug
• Spark plug cap
Reading Diagnosis
Higher than
without oil
• Worn cylinder, piston, and piston ring(s)
Same as
without oil
• Defective piston, piston ring(s), valve(s), and
cylinder head gasket
• Improper valve timing and valve clearance
Spark plug:
20 N·m (2.0 kgf·m, 14 lb·ft)
T
R
.
.