TOHATSU MFS 9.9 Owner's Manual page 117

Power Unit
3. Inspection Items
1) Inspection of Compression Pressure
1. Run engine 5 minutes to warm up, and then stop.
2. Shift gear into neutral (N).
3. Remove lock plate (of stop switch lanyard) from stop switch.
Remove lock plate (of stop switch lanyard)
from stop switch before measuring
compression pressure. This will prevent
engine from accidental starting.
4. Remove all plug caps and then all spark plugs.
Clean areas around spark plugs on the
cylinder before removing spark plugs to
prevent dirt from entering cylinder.
5. Install compression gauge to plug hole.
Compression gauge 1 :
P/N. 3AC-99030-0
6. Fully open throttle, crank engine until compression gauge
indication stabilizes, and then measure compression
pressure.
Compression Pressure (Reference) :650 r/min
With decompressor : 0.50 MPa (73 psi) [5.1 kgf/cm]
Without decompressor : 1.35 MPa (186 psi) [13.8 kgf/cm]
Compression pressure varies depending on the
cranking speed, and normally changes at least
as much as approximately 10%.
7. If compression pressure is below specified value or varies
among cylinders, put small amount of engine oil into
cylinders, and perform the test again.
· If compression pressure of a cylinder
increases after the above measure, check
pistons and piston rings of the cylinder for
wear. Replace if necessary.
· If compression pressure does not increase
after the above measure, check valve
clearances, valves, valve seats, cylinder
sleeves, cylinder head gaskets and cylinder
head. Adjust or replace if necessary.
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CAUTION
CAUTION
1
4st 9.9/15/20 2008