Page G-10
ENGINE
Repair and Service Manual
Read all of Section B and this section before attempting any procedure. Pay particular attention to all Notes, Cautions and Warnings.
B
Fig. 21 Timing Belt Adjustment
COMPRESSION TESTS
Tool List
Qty. Required
Compression gauge .................................................... 1
Spark plug wrench ....................................................... 1
Ratchet, 3/8" drive ....................................................... 1
To prevent inadvertent movement of vehicle,
engage neutral lock per section ‘A’.
Compression tests are one of the most accurate meth-
ods of analyzing engine performance. To obtain maxi-
mum efficiency from the fuel explosion, the combustion
chamber must be sealed. Efficiency can be affected by
problems with rings, pistons, head gaskets and valves.
Most problems associated with these components can
be detected with a cylinder compression gauge. Incor-
rect use of a compression gauge can result in unneces-
sary work and expenditures (Ref. Fig. 22 on Page G-11).
Compression gauge part number 72524-G01 is recom-
mended.
To properly perform an accurate compression test:
1. Remove belt to clutch.
2. Remove the air filter to eliminate the possibility of a
restricted air passage.
3. A well charged good battery should be used. Weak
batteries may not allow the correct cranking speed.
4. Starter belts that drag or slip will affect the compres-
sion reading.
5. Fully open the choke and accelerator baffle plate.
Should either of these baffle plates be partly closed,
the compression reading may be inaccurate and indi-
cate low.
6. The engine must be at normal operating temperature
in order for the components to expand.
To prevent possibility of personal injury, never
operate without spark plug installed in the cyl-
inder not being tested. Fuel drawn into the cyl-
inders will be expelled through the spark plug
opening and could be ignited by the ignition
system or another source, resulting in a fire
7. Remove one spark plug at a time. Removing both
spark plugs may cause the engine to rotate faster than
normal indicating a false reading
and could be a
severe safety problem.
8. Use the starter to rotate the engine until the compres-
sion gauge reading does not change (usually no more
than ten seconds) This is referred as a
dry
compres-
sion test.
9. Record the gauge reading.
10. Pour approximately one half ounce of thirty weight oil
in the cylinder (through the spark plug hole) and
repeat the test. Record the result. The oil added to the
cylinder will cause a temporary seal between the pis-
ton rings, piston and cylinder wall. This is known as
wet
compression.
Thin or very thick oils may cause a false reading.
11. Compare the dry test reading with the wet test read-
ing. A higher wet test reading indicates poor ring seal-
ing or a leaking head gasket (look for oil leakage
around the head gasket). No change between the dry
and wet test indicates valve sealing problems.
Align Notch
and Mark
Align Keyway
with Mark
Remove Cover
to Align Keyway -
Replace After
Aligning
Idler Bolt
(Tighten to
10 - 13 ft. lbs.
(14 - 18 Nm)
torque)
Idler
1/8" - 1/4"
(3 - 6 mm)
Deflection at
10 lbs. (44 N)
'Push'
