Honda Activa SCV110, Service Manual Digest

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7-3
CYLINDER HEAD/VALVES
CYLINDER COMPRESSION
COMPRESSION GAUGE
If the engine must be running to do some work, make
sure the area is well-ventilated. Never run the engine
in an enclosed area.
Warm up the engine to normal operating temperature.
Stop the engine,
Liftup the body cover.
Disconnect the spark plug cap and remove the spark
plug.
Install the compression gauge attachment in a spark plug
hole.
Connect the compression gauge to the attachment.
Open the throttle all the way and crank the engine with the
starter motor or apply kick 5-6 times and check the gauge
reading.
Crank the engine until the gauge reading stops rising.
The maximum reading is usually reached within 4 – 7
seconds.
STANDARD: 843 kPa (8.6 kgf/cm
2
, 122 psi) at
520 min –1 (rpm)
If compression is high, it indicates that carbon deposits
have accumulated on the combustion chamber and/or
the piston crown.
If compression is low, pour 3 – 5 cc (0.1 – 0.2 oz) of clean
engine oil into the cylinder through the spark plug hole
and recheck the compression.
If the compression increases from the previous value,
check the cylinder, piston and piston rings.
• Worn piston ring
• Worn cylinder and piston
If compression is the same as the previous valve, check
the valves for leakage, cylinder head bolt looseness.