Yamaha YBR 125 Generator , Alternator Stator testing

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Yamaha YBR 125 workshop manuals on Ebay UK

Safety Message: When testing the charging system, be cautious of moving engine parts and high-heat areas. Ensure all electrical connections are tight and corrosion-free. Improper testing or short-circuiting stator wires can damage the voltage regulator or the ECU.

The Yamaha YBR 125 Generator / Stator Testing post outlines how to identify and test the core components of the bike's charging and ignition-timing system.

Wiring Identification:

The stator assembly connector typically contains five wires:

3 White Wires: These are the charging coils (stator phases).

Blue Wire: Connected to the neutral switch.

Red and White Wires: Connected to the Crank Position Sensor (pickup coil).

Stator Resistance Testing (Static):

Set your multimeter to the Ohms (Ω) scale.

Unplug the stator connector from the main wiring loom.

Measure the resistance between each of the three white wires (1-2, 1-3, and 2-3).

The readings should be very low and equal across all three pairings (typically around 0.5 to 1.5 Ω depending on the specific model year).

Check for continuity to ground: Touch one probe to a white wire and the other to the engine casing. There should be no continuity (Infinite resistance); if there is, the stator is "shorted to ground."

Voltage Output Testing (Dynamic):

With the engine running and the stator connected, you can measure AC voltage across the white wires. This should increase significantly with RPM (often reaching 50V+ AC at high revs). Note: This requires extreme care and is usually done only if the resistance test is inconclusive.

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3 white stator wires , blue neutral switch , red and white crank sensor .

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