5
5-13
4st 4/5/6 2011
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 plat 1 (of stop switch lanyard) from stop
switch.
6. Fully open throttle, crank engine until compression gauge 2
indication stabilizes, and then measure compression
pressure.
4. Remove all plug caps and then all spark plugs.
5. Install compression gauge 2 to plug hole.
Compression Pressure (Reference) :500 r/min
With decompressor : 0.34 MPa (49.3 psi) [3.5 kgf/cm
2
] ± 10%
Without decompressor
: 0.93 MPa (137.8 psi) [9.5 kgf/cm
2
] ± 10%
(*Remove Exhaust rocker arm)
Remove lock plate (of stop switch lanyard)
from stop switch before measuring
compression pressure. This will prevent
engine from accidental starting.
Clean areas around spark plugs on the
cylinder before removing spark plugs to
prevent dirt from entering cylinder.
Compression gauge 2 :
P/N. 3AC-99030-0
7. If compression pressure is below specified value, put
small amount of engine oil into cylinder, and perform the
test again.
· If compression pressure increases after the
above measure, check pistons and piston rings
for wear. Replace if necessary.
· If compression pressure does not increase
after the above measure, check valve
clearances, valves, valve seats and cylinder
sleeves. Adjust or replace if necessary.
· Compression pressure is affected much by
cranking speed, and normally changes
approximately 10%.
· Do not pull choke knob when measuring
compression pressure.
MFS4-5-6Ech05110425.qxd11.4.2511:39AM ページ13
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