Cylinder Compression - Honda 1998 VT750C Service Manual

CYLINDER HEAD/VALVES
CYLINDER COMPRESSION
mI!ImI _
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 tempera-
ture.
To measure the
Stop the engine, disconnect the spark plug caps and
cylinder
remove one spark plug cap at a time.
compression of
each cylinder,
remove only one
plug at
a
time.
Shift the transmission into neutral.
Front cylinder compression as following:
- Remove the air cleaner housing (page 5-4).
Rear cylinder compression as following:
- Remove the rear cylinder head left side fin (page lD-7).
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.
NOTE:
Crank the engine until the gauge reading stops ris-
ing. The maximum reading is usually reaehed with-
in 4-7 seconds.
STANDARD: 1,275
±
98 kPa (13.0
±
1.0 kgf/cm 2
,
185
±
14 psi) at 400 rpm
If compression is high, it indicates that carbon
deposits have accumulated on the combustion cham-
ber and/or the piston crown.
If compression is low, pour 3 - 5 cc (D.l - D.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.
• Leaking cylinder head gasket
• Worn piston ring
• Worn cylinder and piston
If compression is the same as the previous value,
check the values for leakage.
10-4
PLUG CAP