Yamaha YZF-R125 Service Manual: 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
8-3. 
NOTE:
If the ignition spark gap is within specification, the ignition system circuit is operating normally.
a. Disconnect the spark plug cap from the spark plug.
b. Connect the ignition checker "1" as shown.
2. Spark plug cap
c. Set the main switch to "ON" and the engine
stop switch to "
".
d. Measure the ignition spark gap "a".
e. Crank the engine by pushing the start switch
" 
" and gradually increase the
spark gap until
a misfire occurs.
Checking the ignition coil
1. Check:
Primary coil resistance
Out of specification Replace.
a. Disconnect the ignition coil connectors from
the ignition coil terminals.
b. Connect the pocket tester ( × 1)
to ...
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 crankshaft
position senso ...
Other materials:
Removing the crankshaft
1. Remove:
Crankshaft "1"
NOTE:
Remove the crankshaft with the crankcase
separating tool "2".
Make sure the crankcase separating tool is
centered over the crankshaft.
CAUTION:
To protect the end of the crankshaft, place
an appropriate sized socket between the
c ...
Preparation for removal and disassembly
1. Before removal and disassembly, remove all
dirt, mud, dust and foreign material.
2. Use only the proper tools and cleaning equipment.
Refer to "SPECIAL TOOLS" on page 1-8.
3. When disassembling, always keep mated
parts together. This includes gears, cylinders,
pistons and other part ...
Catalytic converters
This vehicle is equipped with catalytic
converters in the exhaust system.
WARNING
The exhaust system is hot after operation.
To prevent a fire hazard or
burns:
Do not park the vehicle near
possible fire hazards such as
grass or other materials that
easily burn.
Park the vehic ...