A compression gauge (Figure 33) measures combustion chamber (cylinder)
pressure, usually in PSI or kg/ cm
2
. The gauge adapter is either inserted or screwed
into the spark plug hole to obtain the reading. Disable the engine so it does not start
and hold the throttle in the wide-open position when performing a compression test An
engine that does not have adequate compression
cannot be properly tuned. Refer to Chapter Three.
Multimeter
A multimeter (Figure 34) is an essential tool
for electrical system diagnosis. The voltage function
indicates the voltage applied or available to various
electrical components. The ohmmeter function tests
circuits for continuity, or lack of continuity, and
measures the resistance of a circuit.
Some manufacturer’s specifications for electrical components are based on results
using a specific test meter. Results may vary if using a meter not recommended by the
manufacturer. Such requirements are noted when applicable.
Ohmmeter (analog) calibration
Each time an analog ohmmeter is used or if
the scale is changed, the ohmmeter must be
calibrated.
Digital ohmmeters do not require calibration.
1. Make sure the meter battery is in good condition.
2. Make sure the meter probes are in good
condition.
3. Touch the two probes together and observe the
needle location on the ohms scale. The needle
must Align with the 0 mark to obtain accurate measurements.
4. If necessary, rotate the meter ohms adjust knob until the needle and 0 mark align.
Clip-on ammeter
1. Clip-on ammeter (Figure 35) is the basic tool for
electrical system diagnosis which is used to
measure the current of charging system and
other electrical components work current.
2. Clip-on ammeter can measure direct current and
alternating current. Please ensure that the
instrument battery capacity is sufficient when
work.
3. When measure the current, the calliper must
seize the positive pole of the power. If seize the
negative pole mistakenly, wrong result will appear.
Magneto puller
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