Yamaha MTN850-A 2017 Service Manual page 521

c. Measure the primary coil resistance.
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2. Check:
• Secondary coil resistance
Out of specification  Replace.
Secondary coil resistance
9.35–12.65 k
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a. Connect the digital circuit tester () to the ig-
nition coil as shown.
Digital circuit tester (CD732)
90890-03243
Model 88 Multimeter with tachom-
eter
YU-A1927
• Negative tester probe 
red/black "1"
• Positive tester probe 
Spark plug terminal "2"
2
b. Measure the secondary coil resistance.
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EAS30556
CHECKING THE IGNITION SPARK GAP
1. Check:
• Ignition spark gap
Out of specification  Perform the ignition
system troubleshooting, starting with step (5).
Refer to "TROUBLESHOOTING" on page
8-5.
1
2
1
8-164
ELECTRICAL COMPONENTS
Minimum ignition spark gap
6.0 mm (0.24 in)
TIP
If the ignition spark gap is within specification,
the ignition system circuit is operating normally.
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a. Remove the ignition coil from the spark plug.
b. Connect the ignition checker "1" as shown.
Ignition checker
90890-06754
Oppama pet–4000 spark checker
YM-34487
2. Ignition coil
c. Turn the main switch to "ON".
d. Measure the ignition spark gap "a".
e. Crank the engine by pushing the " " side of
the start/engine stop switch and gradually in-
crease the spark gap until a misfire occurs.
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EAS30560
CHECKING THE CRANKSHAFT POSITION
SENSOR
1. Disconnect:
• Crankshaft position sensor coupler
(from the wire harness)
2. Check:
• Crankshaft position sensor resistance
Out of specification  Replace the crank-
shaft position sensor.
Crankshaft position sensor resis-
tance
228–342 
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a. Connect the digital circuit tester () to the
crankshaft position sensor coupler as shown.