Yamaha YZ450F Owner's Service Manual page 190

SPARK GAP TEST
1. Disconnect the spark plug cap
from spark plug.
2. Connect the dynamic spark tester
"1" (ignition checker "2") as
shown.
• Spark plug cap "3"
• Spark plug "4"
A. For USA and CDN
B. Except for USA and CDN
3. Kick the kickstarter crank.
4. Check the ignition spark gap.
5. Start engine, and increase spark
gap until misfire occurs. (for USA
and CDN only)
Minimum spark gap:
6.0 mm (0.24 in)
6. Inspect:
• Sealed portion of spark plug cap
"a"
• Spark plug terminal pin "b"
• Threaded portion of spark plug "c"
7. Inspect:
• Installed condition of spark plug
and spark plug cap
Push in the spark plug cap, mak-
ing sure that it is securely fitted
into the hole in the cylinder head
cover.
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→ Repair or replace.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect:
• Engine stop switch conduction
Tester (+) lead → Black lead "1"
Tester (-) lead → Black lead "2"
Result
Conductive (while the
engine stop switch is
pushed)
Not conductive while it is pushed →
Replace.
Conductive while it is freed → Re-
place.
Set the tester selection position to "Ω
× 1".
CHECKING THE IGNITION COIL
1. Remove the ignition coil cap.
2. Inspect:
• Primary coil resistance
Out of specification → Replace.
Tester (+) lead → Orange lead "1"
Tester (-) lead → Red lead "2"
Primary Tester se-
coil resis- lector posi-
tance
3.57–4.83
Ω at 20°C
(68°F)
7-4
IGNITION SYSTEM
3. Inspect:
• Secondary coil resistance
Out of specification → Replace.
Tester (+) lead → Orange lead "1"
Tester (-) lead → Spark plug termi-
nal "2"
10.71–14.49
kΩ at 20°C
Disconnect the spark plug cap before
measuring the secondary coil resis-
tance.
CHECKING THE AC MAGNETO
1. Inspect:
B B
• Crankshaft position sensor resis-
tance
Out of specification → Replace.
Tester (+) lead → Gray lead "1"
Tester (-) lead → Black lead "2"
tion
Ω × 1
Secondary Tester se-
coil resis- lector posi-
tance tion
kΩ × 1
(68°F)
Crankshaft Tester se-
position lector posi-
sensor re- tion
sistance
248–372 Ω
at 20°C Ω × 100
(68°F)
Gy B