Cylinder Compression Test; Cylinder Head Inspection - TOHATSU BFT75A Service Manual

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CYLINDER HEAD

CYLINDER COMPRESSION TEST

Set the remote control lever in the "N" (neutral) position.
Remove the emergency stop switch clip.
Disconnect all the injector 2P connectors.
Disconnect the ignition coil 3P connector of each
cylinder, and remove the spark plugs (page 3-15).
Disconnect the remote control cable from the throttle
arm (page 19-8).
Install the compression gauge (commercially available:
EEPV303A) [1] in the No.1 plug hole.
Set the throttle arm in the full open position by pushing
the throttle arm [2] against the full throttle stopper by
hand as shown.
Turn the combination switch to the "START" position
and operate the starter motor to measure the cylinder
compression.
CYLINDER COMPRESSION (Pressure check at 300
min -1 (rpm) with "N" (neutral) position):
1.45 – 1.65 MPa (14.8 – 16.8 kgf/cm
Check the compression on all cylinders.

CYLINDER HEAD INSPECTION

VALVE SPRING FREE LENGTH
Measure the free length of the valve springs.
STANDARD:
IN: 48.54 mm (1.911 in)
EX: 55.29 mm (2.177 in)
VALVE FACE/STEM O.D.
Inspect each valve face [1] for pitting or wear
irregularities.
Check each valve face for even seat.
Replace the valve if necessary.
Check each valve for bends, seizure, or damage.
Measure the valve stem O.D. at the sliding surface of
the valve guide.
STANDARD:
IN: 5.480 – 5.490 mm (0.2157 – 0.2161 in)
EX: 5.450 – 5.460 mm (0.2146 – 0.2150 in)
SERVICE LIMIT:
IN: 5.450 mm (0.2146 in)
EX: 5.420 mm (0.2134 in)
If the measurement is less than the service limit,
replace the valve with a new one.
14-32
2
, 211 – 239 psi)
[1]
[2]
[1]