Yamaha YZF-R125 Owners Manual: Troubleshooting

Although Yamaha motorcycles receive a thorough inspection before shipment from the factory, trouble may occur during operation. Any problem in the fuel, compression, or ignition systems, for example, can cause poor starting and loss of power.

The following troubleshooting charts represent quick and easy procedures for checking these vital systems yourself. However, should your motorcycle require any repair, take it to a Yamaha dealer, whose skilled technicians have the necessary tools, experience, and know-how to service the motorcycle properly.

Use only genuine Yamaha replacement parts. Imitation parts may look like Yamaha parts, but they are often inferior, have a shorter service life and can lead to expensive repair bills.

WARNING
When checking the fuel system, do not smoke, and make sure there are no open flames or sparks in the area, including pilot lights from water heaters or furnaces. Gasoline or gasoline vapors can ignite or explode, causing severe injury or property damage.

    Rear wheel
    To remove the rear wheel WARNING To avoid injury, securely support the vehicle so there is no danger of it falling over. Loosen the axle nut. Axle nut Drive chain slack adjust ...

    Troubleshooting charts
    Starting problems or poor engine performance Starting problems or poor engine performance Engine overheating WARNING Do not remove the radiator cap when the engine and radiator are hot. S ...

    Other materials:

    Disassembling the water pump
    1. Remove: Water pump seal "1" NOTE: Remove the water pump seal from the inside of the water pump housing "2". 2. Remove: Bearing "1" NOTE: Remove the bearing from the outside of the water pump housing "2". ...

    Throttle position sensor
    1. Check: Throttle position sensor a. Connect the digital circuit tester to the terminals of the throttle body sensor assembly coupler as shown. Positive tester probe → gray/red terminal "1" Negative tester probe → gray/black terminal "2" b. Measure the throttle pos ...

    Checking the starter motor
    1. Check: Commutator Dirt Clean with 600 grit sandpaper. 2. Measure: Commutator diameter "a" Out of specification Replace the starter motor. 3. Measure: Mica undercut "a" Out of specification Scrape the mica to the proper measurement with a hacksaw blade ...

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