Vanguard OHV V-Twin User Manual page 31

Cylinder Leakdown Test
Use a leakdown tester to test the sealing capability
of each cylinder. Follow the instructions for the leak-
down tester you are using to determine the likely
problem area(s).
1. Run engine for 5 minutes allowing engine to
reach operating temperature.
NOTE: If the engine is cold or cannot be started, air
flow may be higher (gauge readings lower)
because compression components are not
at normal operating temperatures.
2. Remove spark plug from engine. Disconnect
crankcase breather tube.
3. Rotate crankshaft in direction of operation until
piston is at Top Dead Center (TDC) of the com-
pression stroke.
4. Hold flywheel nut with socket and breaker bar.
NOTE: Hold the crankshaft with the piston at TDC
to minimize the chance of rotation.
AVOID INJURY!
• Injury could occur if the crankshaft is
allowed to rotate or if the engine is not
securely fastened to a stand or to the
application.
5. Connect tester to a shop air source with
minimum air pressure of 70 psi (480 kPa).
6. Install outlet hose into spark plug hole of cylinder
being tested. Insure O-ring is seated to prevent
air leak at spark plug hole. Connect other end to
tester.
7. While securely holding the flywheel nut with the
breaker bar and socket, pull the adjustment
knob OUT (arrow), Fig. 4. Slowly turn the regula-
tor adjustment knob (1) CLOCKWISE until tester
needle (2) is on the set point. Push in regulator
adjustment knob.
NOTE: Any air leaks at connections or fittings of
tester will affect the accuracy of test.
8. Slowly open the valve and note the reading on
the gauge.
30
CAUTION
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Fig. 4
Cylinder Balance Test
If the engine starts hard, runs rough, misses or lacks
power, perform a cylinder balance test to determine
whether both cylinders are operating correctly.
A cylinder balance test will also detect a cylinder that
is not functioning. When grounding one cylinder
there will be no RPM loss. When the other cylinder
is grounded the engine will stop.
• Tools Required:
Tachometer #19200
Two @ Ignition Tester #19368
Screwdriver with insulated handle.
1. Attach Ignition Tester #19368 (2) between each
spark plug lead (1) and spark plug (3), Fig. 5.
Fig. 5
2. Start engine. Run at top no-load speed and note
spark at ignition testers. If the spark is equal at
both ignition testers, the problem is not ignition
related. A spark miss should be readily
apparent.
3. Note RPM of engine. Ground one cylinder with
screwdriver (4) by contacting alligator clip on
ignition tester to a good ground on engine,
Fig. 6. Note RPM loss.
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