Power Unit; Checking The Compression Pressure - Yamaha 250GETO Service Manual

POWR

Power unit

Checking the compression pressure

1. Start the engine, warm it up for 5 min-
utes, and then turn it off.
2. Remove the lock plate from the engine
stop lanyard switch on the remote control
box or switch panel.
3. Remove the all spark plug caps and all
spark plugs, and then install the special
service tools into a spark plug hole.
cC
Before removing the spark plugs, blow
compressed air in the spark plug well to
clear out any dirt or dust that may fall into
the cylinder.
Compression gauge:
90890-03160
4. Fully open the throttle, and then crank the
engine until the reading on the compres-
sion gauge stabilizes.
NOTE:
Disconnect the choke solenoid blue lead from
the wireharness.
Minimum compression pressure
(reference data):
430 kPa (4.3 kgf/cm
5-1
Power unit
6S350690
2 , 61 psi)
5. If the compression pressure is below
specification and the compression pres-
sure for each cylinder is unbalanced, add
a small amount of engine oil to the cylin-
ders, and then check the compression
pressure again.
NOTE:
9 If the compression pressure increases,
check the pistons and piston rings for wear.
Replace if necessary.
9 If the compression pressure does not
increase, check the cylinder head gasket,
and cylinder head. Replace if necessary.
6S35H11