Checking The Compression Pressure; Checking The Oil Pressure; Removing The Power Unit - Yamaha FT50C Service Manual

POWR

Checking the compression pressure

1. Start the engine, warm it up for 5 min-
utes, and then turn it off.
2. Remove the clip from the engine shut-off
switch on the remote control box or tiller
handle.
3. Remove the all spark plugs, and then
install the special service tool to each
spark plug hole.
CAUTION:
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 1:
90890-03160
4. Fully open the throttle, crank the engine
until the reading on the compression
gauge stabilizes, and then check the
compression pressure.
Minimum compression pressure:
840 kPa (8.4 kgf/cm
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-
der, and then check the pressure again.
NOTE:
• If the compression pressure increases,
check the piston and piston rings for wear.
Replace if necessary.
5-13
Power unit
2
, 122 psi)
• If the compression pressure does not
increase, check the valve clearance, valve,
valve seat, cylinder sleeve, cylinder head
gasket, and cylinder head. Adjust or
replace if necessary.

Checking the oil pressure

1. Start the engine, warm it up for 5 min-
utes, and then turn it off.
2. Remove the oil pressure switch, and then
install an oil pressure gauge 1 to the oil
pressure switch installation hole.
NOTE:
Use a pressure gauge with an adapter with a
1/8 pitch thread.
3. Check the oil pressure. Check the oil
pump, oil suction pipe, and oil strainer if
out of specification.
Oil pressure:
100 kPa (1.0 kgf/cm
idle speed (850–950 r/min)

Removing the power unit

1. Remove the flywheel magnet cover and
flywheel magnet.
2
, 14 psi) at
62Y5A11