1D-2 Engine Mechanical:
Diagnostic Information and Procedures
Compression Pressure Check
B649G11404001
The compression pressure reading of a cylinder is a
good indicator of its internal condition.
The decision to overhaul the cylinder is often based on
the results of a compression test. Periodic maintenance
records kept at your dealership should include
compression readings for each maintenance service.
NOTE
• Before checking the engine for
compression pressure, make sure that the
cylinder head nuts are tightened to the
specified torque values and the valves are
properly adjusted.
• Make sure that the battery is in fully-
charged condition.
1) Warm up the engine.
2) Remove the fuel tank. Refer to “Fuel Tank Removal
and Installation: in Section 1G”.
3) Remove all of the spark plugs.
4) Remove the frame head cover, left and right.
(GSF1200) Refer to “Exterior Parts Removal and
Installation: in Section 9D”.
5) Install the compression gauge and adaptor in one of
the spark plug holes. Make sure that the connection
is tight.
Special tool
(A): 09915–64510 (Compression gauge set)
(B): 09915–63210 (Compression gauge
adaptor)
6) Keep the throttle grip in the fully-opened position.
7) Press the starter button and crank the engine for a
few seconds. Record the maximum gauge reading
as the cylinder compression.
8) Repeat this procedure with the other cylinders.
Compression pressure specification
Low compression pressure can indicate any of
the following conditions:
• Excessively worn cylinder walls
• Worn piston or piston rings
• Piston rings stuck in grooves
• Poor valve seating
• Ruptured or otherwise defective cylinder head
gasket
Overhaul the engine in the following cases:
• Compression pressure in one of the cylinders is
less than 875 kPa (8.75 kgf/cm
2
, 124 psi)
• The difference in compression pressure between
any two cylinders is more than 200 kPa (2 kgf/
cm
2
, 124 psi)
• All compression pressure readings are below 1
000 kPa (10 kgf/cm
2
, 142 psi) even when they
measure more than 875 kPa (8.75 kgf/cm
2
, 124
psi)
9) After checking the compression pressure, reinstall
the removed parts.
(A)
(B)
I649G1140310-01
Standard Limit Difference
1 250 kPa
(12.5 kgf/cm
2
,
178 psi)
875 kPa
(8.75 kgf/cm
2
,
124 psi)
200 kPa
(2 kgf/cm
2
, 28
psi)
I649G1140311-01
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