Replace it if necessary.

Inner Tube Inspection
Spring Tension InspectionCylinder Compression Measurement
NOTE
Use the battery which is fully charged.
Warm up the engine thoroughly.
Stop the engine.
Remove the spark plugs (see Spark Plug Replacement in
the Periodic Maintenance chapter).
Attach the compression gauge [A] and adapter [B] firmly
into the spark plug hole.
Using the startermo ...
For Primary Fuel Injectors
Remove the air cleaner housing (see Air Cleaner Housing
Removal).
Disconnect the primary fuel injector connector [A].
Connect a digital meter to the terminals in each primary
fuel injector [A].
Measure the primary fuel injector resistance.
Primary Fuel Injector Resistance ...
Brake Line Bleeding
The brake fluid has a very low compression coefficient so
that almost all the movement of the brake lever or pedal
is transmitted directly to the caliper for braking action. Air,
however, is easily compressed. When air enters the brake
lines, brake lever or pedal movement will be partially used
...