Wiring Connections; Checking The Magneto Charge Coil And Pulser Coil; Ignition Timing; Spark Gap Test - Yamaha QT 50F Service Manual

The SCR becomes conductive when the
signal voltage exceeds a certain level
(trigger level). The ignition timing differs
with the signal voltage, which in turn
changes with engine speed. (Show
below)
Volt
,1-High engine speed
Middle engine speed
Low engine speed
• Trigger voltage
(0.7 volt)
T.D.C.
Crank angle
Pulser coil
Charge coil
(W/R)20fi±10%
(B/R)295fl±10%
Pocket tester
\
r H
White/Red
Q: —
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I
Black/Red
Ttr C.D.I, magneto
O. Ignition Timing
See Chapter 2-5 for Ignition Timing
B. Wiring Connections
The wiring between the magneto, C.D.I, unit,
and ignition coil uses couplers to prevent any
wrong connection.
When connecting the ground circuit and the
ignition coil, particular care should be taken.
If these are connected wrong, the C.D.I, unit
will become inoperative.
1. Wiring Notes
a. Connection must be done accurately.
Special care is required for connection
of the ground circuit and ignition coil.
b. The C.D.I, unit and ignition coil should
be installed in the specified positions. If
position is to be changed, a dry and air
place should be selected. Keep free
from mud and water.
c. To remove the rotor, be sure to use the
flywheel magneto puller. Avoid using a
hammer, or the rotor may be damaged.
d. Handle the C.D.I, unit with special care.
If you should drop it, the incorporated
electronic components will be damaged.
C. Checking the Magneto Charge Coil
and Pulser Coil
The resistance of the magneto charge coil
and pulser coil are as specified below. To
locate the cause of trouble (broken coil,
short-circuit etc.), measure the resistance
across eac lead as shown in chart.
E. Spark Gap Test
The entire ignition system can be checked for
misfire and weak spark using the Electro
Tester. If the ignition system will fire across a
sufficient gap, the engine ignition system can
be considered good. If not, proceed with
individual component tests until the problem
is found.
1. Warm up engine thoroughly so that all
electrical components are at operating
temperature.
2. Stop engine and connect tester as
shown.
1. Electro-tester
2. Plug wire from coil
3. Sparkplug
't
V
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