Yamaha YBR 125 injector testing .
other posts of interest
Yamaha YBR 125 Fuel Injection System , FI diagnostics
Yamaha YBR 125 Diagnostic Fault codes
I have not had any problems with any injectors i have come across on the YBR 125 , i did once wire one up incorrectly which gave an injector fault but that was my fault .
i have even had customers buy injectors from me after questioning and they were convinced the injector was at fault only for them to bring it back a few days later .
Do yourself and the person your buying parts from a favour and test the components , all the tests you need to do are in the Yamaha YBR 125 Haynes manual so buy one and save money , do not just randomly buy components hoping to guess correctly it rarely works .
you can easily hear the injector firing when the engine is running , or you can check the fault codes -
see out injector fault codes post here .
you can also use the Yamaha FI fuel injection diagnostics machine , which simulates 5 x fires of the
injector to test them , if you have access to one its and excellent tool to own . see our Yamaha FI diagnostics post here .
Testing Yamaha YBR 125 Injector resistance value
I have not seen an actual figure for this but i have got 3 x functioning Yamaha YBR 125 Injectors here
are all test up to 12 ohms .
easy to do set Multi meter to ohms ( auto ) and test between both terminals
 |
| 12.5 ohms |
Since my original 2021 guide, I’ve found that many "injector issues" are actually electrical. Before you buy a replacement or start a messy cleaning process, you should perform an Ohmic Resilience Test. This tells you if the internal solenoid coil is healthy or if it has "Maintenance Debt" that can’t be fixed with a cleaner.
1. The Resistance Test (The "Health" Check)
This is the most important test. You are checking the internal copper winding of the injector.
Set your Multimeter to: 200 Ohms (Ω).
Procedure: Disconnect the electrical plug from the injector. Place your probes on the two metal pins inside the injector's socket.
The Magic Number: A healthy YBR 125 injector should read between 12.0 and 15.0 Ohms at room temperature.
Verdict: * 0.0 – 2.0 Ω: The injector is "Shorted"—it will likely blow a fuse or damage your ECU.
"OL" or 1 (Infinite): The coil is "Open"—it’s dead and will never fire.
15.0+ Ω: The coil is failing or heat-damaged.
2. The Voltage Feed Test
If the injector is healthy, you need to make sure the bike is actually telling it to fire.
Set your Multimeter to: 20V DC.
Procedure: Turn the ignition ON (engine off). Probe the connector pins (the wire side, not the injector side).
The Result: You should see roughly 12V (Battery Voltage) on one of the pins. The ECU "pulses" the ground side to fire the injector, so you are looking for that steady power feed first.
3. Testing for a "Sticky" Injector
Sometimes the electrics are perfect, but the mechanical "pintle" inside is stuck due to E10 fuel gumming.
The Click Test: Use your multimeter's "Continuity" (Beep) mode or a 9V battery to briefly pulse the injector. If you don't hear a sharp, metallic click, the internal spring is stuck.
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