Yamaha XS750, Manual, Page: 129 / 154

Standard values:
Primary coil resistance:
4.0 ohms ± 10% at 20°C (68°F)
Secondary coil resistance
11.0K ohms ± 20% at 20°C (68°F)
Insulation
test.
a. Connect ohmmeter as shown (ohms x 1,000
or more).
b. Resistance reading should be or
at least
3M ohms. I f less, replace.
E. Condenser Test
If the contact points show excessive wear, or the
spark is weak (but the ignition coil is in good con-
dition), check the condenser.
1. Capacity
test
(use Electro Tester).
INSULATION TEST.
a.
Calibrate capacity scale.
b. Connect tester
c. Meter needle will deflect and return to
center
as
condenser is charged. After needle
stops, note reading on scale.
I
Condenser capacity:
±
10%
I
CAUTION: After this measurement, the con-
denser should be discharged by shorting the
positive lead wire t o the condenser case.
6 - 4 SPARK PLUG
The life of a spark plug and it s discoloring vary ac-
cording to the habits of the rider. A t each periodic
inspection, replace burned or fouled plugs with suit-
able ones determined by the color and condition of
the
bad plugs. One machine may be ridden only in
urban areas a t low speeds; another may be ridden for
hours at high speed. Confirm what the present plugs
indicate by asking the rider how long and how fast he
rides. Recommend a hot, standard, or cold plug type
accordingly. I t
is
actually economical to install new
plugs often since it will tend
to
keep theengine in good
condition and prevent excessive fuel consumption.
A. How To "Read" A Spark Plug (Condition)
1. Best condition: When the porcelain around
the center electrode is a light tan color.
2. I f the electrodes and porcelain are black and
somewhat oily, replace the plug with a hotter
type for low speed riding.
3.
I f the porcelain is burned or glazed white
and/or the electrodes are partially burned
away, replace the plug with
a
colder type for
high speed riding.
B. Inspection
Instruct the rider to:
1. Inspect and clean the spark plug every 3,200km
(2,000 miles).
2. Clean the electrodes of carbon and adjust the
electrode gap.
3.
Be sure to use the proper reach plug as a re-
placement to avoid overheating, fouling or
piston damage.
I
Spark plug type: N-7Y (Champion) or
I
BP-7ES (NGK)
Spark plug gap: 0.7~0.8mm (0.028~0.031")
6-5 LIGHTING AND SIGNAL SYSTEMS
A. Lighting Tests and Checks
The battery provides power for operation of the horn,
tail light, stop light, neutral light, and flasher light. If
The battery provides power for operation o f the horn,
The battery provides power for operation of the horn,
tail light, stop light, neutral light, and flasher light. If
none of the above operates, always check battery
voltage before proceeding further. Low battery vol-
tage
indicates either a faulty battery, low battery
water, or a defective charging system. See section