Monday, 14 March 2022

Testing the YZF-R125 Neutral Light Switch

 

⚠️ Safety Warning: When testing or replacing the neutral light switch, ensure the motorcycle is on a stable paddock stand or the sidestand. If the switch fails, the bike may not start even when in neutral, or it might allow the starter to engage while in gear, causing the bike to lurch forward. Always verify that the rear wheel can spin freely before starting the engine during electrical testing.

The neutral light switch is a simple but critical component for both rider information and the safety lockout system. This guide covers how to test a single-wire switch (common on R125 and WR125 models).


Location

  • The switch is located on the engine casing, just to the left-hand side of the gear selector shaft.

Testing Procedure

To confirm if the switch is functioning, you will need a multimeter set to the continuity (beep) setting:

  1. Internal Continuity: Place one probe on the terminal inside the switch and the other on the metal contact point inside. There should be a continuous connection (a beep).

  2. Isolation Test: Place one probe on the terminal and the other on the body/housing of the switch. There should be NO continuity here. If it beeps, the switch is shorted to earth internally and must be replaced.

  3. On-Bike Test: With the switch installed, the wire should ground to the engine casing only when the gearbox is in neutral.

Symptoms of Failure

  • The neutral "N" light on the dashboard does not illuminate.

  • The bike will only start with the clutch pulled in, even if it is in neutral.

  • Intermittent flickers of the neutral light while riding.


Parts & Tools


Easy to test ensure there is continuity through the inside of the switch but not to earth or body of the switch. 


Its located just to the left hand side of the gear selector shaft location.



                                       See video of this entire process below 


Testing single wire Neutral light switch ( R125 WR 125 )

Test for continuity through the switch 

Testing single wire Neutral light switch ( R125 WR 125 )

And make sure there is none to the body of the switch from the terminal 

Testing single wire Neutral light switch ( R125 WR 125 )

Testing single wire Neutral light switch ( R125 WR 125 )


See this entire process in video below 








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