Yamaha YZF-R125 Service Manual: Checking the horn
1. Check:
Horn resistance
Out of specification 
Replace.
a. Disconnect the horn connectors from the horn terminals.
b. Connect the pocket tester ( × 1) to the horn
terminals.
- Positive tester probe
horn terminal "1" - Negative tester probe
horn terminal "2"
c. Measure the horn resistance.
2. Check:
Horn sound
Faulty sound Adjust or replace.
a. Connect a battery (12 V) to the horn.
b. Turn the adjusting screw in direction "a" or "b" until the specified horn sound is obtained.
Checking the rectifier/regulator
1. Check:
Rectifier/regulator output voltage
Out of specification → Replace the
rectifier/
regulator.
a. Set the engine tachometer to the spark plug
lead.
b. Connect the pocket tester ...
Checking the fuel sender
1. Drain the fuel from the fuel tank.
2. Check:
Fuel sender resistance
Out of specification → Replace the fuel
sender.
a. Connect the pocket tester ( ×
10) to the fuel
sender c ...
Other materials:
Adjusting the valve clearance
The following procedure applies to all of the
valves.
NOTE:
Valve clearance adjustment should be made
on a cold engine, at room temperature.
When the valve clearance is to be measured or
adjusted, the piston must be at top dead center
(TDC) on the compression stroke.
1. Remove:
...
Electrical components
1. Main switch
2. Clutch switch
3. Front brake light switch
4. Ignition coil
5. Throttle body sensor assembly (intake air
pressure sensor, intake air temperature
sensor, throttle position sensor)
6. FID (fast idle solenoid)
7. Rectifier/regulator
8. Lean angle sensor
9. Starting circui ...
Outline of the fi system
The main function of a fuel supply system is to provide fuel to the
combustion chamber at the optimum
air-fuel ratio in accordance with the engine operating conditions and the
atmospheric temperature. In
the conventional carburetor system, the air-fuel ratio of the mixture that is
supplied t ...