Yamaha YZ125(D) Owner's Service Manual page 154

SPARK GAP TEST
1. Disconnect the spark plug cap
from spark plug.
2. Connect the dynamic spark tester
"1" (ignition checker "2") as
shown.
• Ignition coil "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)
CHECKING THE COUPLERS,
LEADS AND IGNITION COIL
CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-cir-
cuit → Repair or replace.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect:
• Engine stop switch conduction
Tester (+) lead→Black/White 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. Inspect:
• Primary coil resistance
Out of specification → Replace.
Tester (+) lead → Yellow lead "1"
Tester (-) lead → Black lead "2"
Primary Tester se-
coil resis- lector posi-
tance
0.24–0.36
Ω at 20 °C
(68 °F)
2. Inspect:
• Secondary coil resistance
Out of specification → Replace.
Tester (+) lead → Spark plug lead
"1"
Tester (-) lead → Yellow lead "2"
6-4
IGNITION SYSTEM
5.7–8.5
kΩat 20 °C
(68 °F)
• Remove the spark plug cap by turn-
ing it counterclockwise and inspect.
• Install the spark plug cap by turning
it clockwise until it is tight.
CHECKING THE SPARK PLUG
CAP
1. Inspect:
• Spark plug cap
Loose connection → Tighten.
Deteriorated/damaged → Re-
place.
• Spark plug cap resistance
Out of specification → Replace.
tion
Tester (+) lead → Spark plug lead
terminal "1"
Ω × 1
Tester (-) lead → Spark plug termi-
nal "2"
4–6 kΩ at
20 °C (68
°F)
Secondary Tester se-
coil resis- lector posi-
tance tion
kΩ × 1
Spark plug Tester se-
cap resis- lector posi-
tance tion
kΩ × 1