Yamaha MX-800, Service Manual

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ENGINE
3-1
ENGINE
ENGINE INSPECTION
MEASURING THE COMPRESSION PRESSURE
The following procedure applies to all of the cylinders.
TIP
Measure the compression pressure after checking and
adjusting the valve clearance.
1.
Warm up the engine for several minutes.
2.
Remove:
• Spark plug cap
• Spark plug
3.
Connect:
• Engine compression tester “1”
• Extension “2”
4.
Measure:
• Compression pressure
Open the throttle and crank the engine until the
needle stop rising on the engine compression tes-
ter.
Out of specification

Refer to steps (a) and (b).
Before removing the spark plug, use compressed air
to clean the cylinder head cover to prevent dirt from
falling into the engine.
NOTICE
1
2
Engine compression tester:
YU-33223
Standard compression pressure:
1.31–1.45 MPa (13.4–14.8 kg/cm², 190–210
psi)
Limit:
1.03 MPa (10.3 kg/cm², 150 psi)
To prevent sparking the plugs, remove all ignition coil
couplers and fuel injector couplers before cranking
the engine.
WARNING