Ignition Coil; Spark Plug - Yamaha BR250F Service Manual

E. Ignition Coil
1. Coil spark gap test
a. Remove the ignition coil from the frame.
b. Connect the Electro Tester as shown.
c. Connect a fully charged battery to the
tester.
d. Turn on the spark gap switch, and in-
crease the gap until misfire occurs.
nx
1
63
0 0 1 - - - - - - +...
Minimum spark gap: 9 mm (0.35 in)
1. Battery 2. 6 mm (0.24 in)
Spark plug color
No.1
Good (Carburetor is tuned properly.)
No.2
Bad (Mixture is too rich.)
Replace main jet with one-step small one.
No.3
Bad (Mixture is too lean.)
Replace main jet with one-step larger one.
Bad (Due to too lean a mixture, piston is
damaged or seized.)
No.4
Replace the piston and spark plug.
Tune the carburetor again, starting with
low-speed tuning.
Bad (Due to too lean
a
mixture, the en-
gine knocks.)
Check the piston for holes or seizure.
No.5
Check the cooling system, gasoline octane
rating and ignition timing. After replacing
the spark plug, tune the carburetor again,
starting with low-speed tuning.
Bad (Due to lean a mixture, the spark
plug rnelts.)
Check the piston for holes or seizure.
No.6
Check the cooling system, gasoline octane
rating and ignition timing. After replacing
the spark plug with colder type, tune the
carburetor again starting with low-speed
,tuning.
----fIIo'-
Primary coil resistance
---..... Secondary coil resistance
F.
Spark
Plu9
The I ife of a spark plug and its condition vary
according to the habits of the rider. You can
learn a great deal about the operating condi-
tion of an engine by studying the spark plug.
Examine the spark plug at each periodic
inspection, and replace it with a suitable plug.
Ask the customer how long and how fast
he rides his snowmobile, and recommend a
hot, standard, or cold plug accordingly.
Encourage your customers to change the
spark plug regularily. Their snowmobiles will
run better, and fuel consumption will remain
low.
Secondary coil
resistance
5.9 kn ± 20%
at 20°C (68°F)
Primary coil
resistance
1.0n
±
10%
at 20°C (68
0
F)
2. Coil winding resistance tests
Use a pocket tester to determine resist-
ance and continuity of the primary and
secondary coil windings.
MITSUBISH
F6T411
Manufacturer
6-4