CYLINDER COMPRESSION. Honda CBR125R

CYLINDER HEAD/VALVES

CYLINDER COMPRESSION

Warm the engine to normal operating temperature.

Stop the engine.

Remove the spark plug (page 3-9).

Install the compression gauge attachment into the spark plug hole.

Connect the compression gauge to the attachment.

TOOL:

Compression gauge attachment 07RMJ-MY50100 or equivalent commercially available

To avoid discharging the battery, do not operate the starter motor for more than 7 seconds.

Turn the ignition switch ON (and engine stop switch

" ": CM and U type).

Shift the transmission into neutral.

Crank the engine with the starter motor.

Open the throttle all the way and crank the engine with the starter motor until the gauge reading stops rising.

STANDARD:

1,343 kPa (13.7 kgf/cm

2

, 195 psi) at 530 min

-1

(rpm)

Low compression can be caused by:

– Blown cylinder head gasket

– Improper valve adjustment

– Valve leakage

– Worn piston ring or cylinder

High compression can be caused by:

– Carbon deposits in combustion chamber or on piston head

CYLINDER HEAD COVER

REMOVAL

Remove the middle cowl (page 2-9).

The cylinder head cover can be serviced with the engine installed in the frame.

Remove the radiator lower mounting bolt, then move the radiator forward.

COMPRESSION GAUGE

COMPRESSION GAUGE ATTACHMENT

BOLT RADIATOR

8-6

CYLINDER HEAD/VALVES

Remove the cylinder head cover bolts, rubber seals, cylinder head cover and packing.

BOLTS/RUBBER SEALS

INSTALLATION

Install a new packing into the cylinder head cover groove.

Install the cylinder head cover onto the cylinder head.

COVER/PACKING

PACKING COVER

Check the rubber seals are in good condition, replace them if necessary.

Install the rubber seals to the cylinder head cover with their "UP" marks facing up.

"UP" MARKS

RUBBER SEALS

Install and tighten the cylinder head cover bolts to the specified torque.

TORQUE: 10 N·m (1.0 kgf·m, 7 lbf·ft)

BOLTS

8-7