Inspection Items - TOHATSU MFS25 Service Manual

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 from stop switch.
Remove lock plate 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) :
1.13 MPa ( 164 PSI ) [ 11.5 kgf/cm
Compression pressure is affected much by cranking
speed, and normally changes 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.
5-18
CAUTION
CAUTION
] ±10 %
2
1
25/30 2006