Yamaha YZF-R125 Service Manual: Checking the lean angle sensor
1. Remove:
- Lean angle sensor
2. Check:
Lean angle sensor output voltage
Out of specification 
Replace.
a. Connect the lean angle sensor to the wire harness.
b. Connect the pocket tester (DC 20 V) to the
lean angle sensor coupler as shown.
Positive tester probe 
yellow/green "1"
Negative tester probe 
gray/black "2"
c. Set the main switch to "ON".
d. Tilt the lean angle sensor to 65.
e. Measure the lean angle sensor output voltage.
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 ...
Checking the starter motor operation
1. Check:
Starter motor operation
Does not operate → Perform the electric
starting system troubleshooting, starting with
step 4.
Refer to "TROUBLESHOOTING" on page
8-9.
a. Con ...
Other materials:
Removing the cylinder head
1. Align:
"I" mark "a" on the generator rotor
(with the stationary pointer "b" on the generator
cover)
a. Turn the crankshaft counterclockwise.
b. When the piston is at TDC on the compression
stroke, align the "I" mark "c" on the camshaft
sprocket with the mark "d" on the
cylinder h ...
Removing the front brake caliper
NOTE:
Before disassembling the brake caliper, drain
the brake fluid from the entire brake system.
1. Remove:
Brake hose union bolt "1"
Copper washers "2"
Brake hose "3"
NOTE:
Put the end of the brake hose into a container
and pump out the brake fluid carefully.
...
Removing the rear brake master cylinder
NOTE:
Before removing the rear brake master cylinder,
drain the brake fluid from the entire brake system.
1. Disconnect:
Rear brake light switch coupler
2. Loosen:
Rear brake light switch "1"
3. Remove:
Rear brake master cylinder bolts
Rear brake master cylinder
4. Remove:
...