(2) Shut off the engine and remove all spark plugs.
(3) Install the compression tester (1) in the spark plug hole. Make sure that the rubber adapter of the tester
makes an airtight contact with the cylinder head (2).
(4) Crank the engine with the starter and observe the readings on the compression tester (1). Record the
highest reading.
(5) Repeat the test on the rest of the cylinders. If the reading on the compression tester is from 90 to 110
pounds at sea level and not varying more than 10 pounds between cylinders, the compression pressure can
be considered normal.
(6) If the pressure of any cylinder is weak, inject oil through the spark-plug hole onto the top of the piston, with
the piston down. Wait a few minutes for the oil to run down over the piston rings so it will not get on the
valves.
(7) Repeat the compression test. If the reading is still low, the valves are leaking and a valve grinding job is
needed (par. 136).
(8) If the reading is high, the piston rings are leaking and must be replaced.
(9) An extremely low reading between two adjacent cylinders indicates a leaky cylinder head gasket. Inspect
and replace the gasket (par. 135).
Section XII. MASTER, FORWARD AND REVERSE CLUTCHES
138. Master Clutch
a. General. The master clutch (fig. 55) is engaged by toggle action. When the sliding sleeve cone (2) is moved
towards the clutch, the machined ends of the four finger levers (13) contact a ring on a floating plate (6). The floating
plate has a special heat-treated insert to prevent the finger levers (13) from biting and cutting into it. When pressure is
applied to the sliding sleeve cone (2), the links (14) move forward and engage the clutch. When the sliding sleeve cone
(2) is moved away from the clutch, pressure against the floating plate (6) is released and the clutch becomes disengaged.
b. Adjustment (fig. 56).
(1) A new clutch may require several adjustments until all moving parts are worn in.
(2) Disengage the clutch before making clutch adjustments.
(3) Turn the clutch until the adjusting lock pin (12) can be reached. The clutch is accessible through the
openings in the flywheel housing.
(4) Pullout the adjusting lock pin (12).
(5) Push a short piece of wire through the small cross-drilled hole in the adjusting lock pin (12) and lock the pin
in the "out" position.
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