9 Most Common Problems With Yamaha YZF R125 (Explained)

The Yamaha YZF R125 is currently in its third generation, and since its introduction in 2008, the R125 has been a mini-ripper fan favorite.

The YZF R125 is a small-displacement four-stroke sport bike with a digital LCD display, Yamaha-racer-style bodywork, and a powerful little motor equipped with smooth-performance-enhancing Variable Valve Actuation.

But no bike is perfect – just what are the common problems with the Yamaha YZF R125?

We’ve listed them all below!

1. Yamaha YZF R125 Won’t Start

The Yamaha YZF R125 has one of the most impressive and reliable engines in the small-displacement four-stroke game.

That said, motorcycle riding variables can stop any motorcycle from starting; the R125 isn’t immune to at least a few of the common moto-starting problems.

The first thing to do if your Yamaha YZF R125 won’t start is to spray starting fluid, or ether, into your airbox, as the most common reason one of these bikes won’t start is a clogged air intake.

Luckily, this is one of the most straightforward tasks to accomplish;

  1. The ether-based starter fluid suggested by Yamaha probably comes in a spray can – use it to spray your air box so that it’s covered in a light coat of mist. You don’t want it soaking wet.
  2. If the bike starts up, the dirt-clogged air intake was your problem, and you’ve solved it!
  3. If the bike doesn’t start up, move on to investigating your spark plugs. Scroll down to the ‘No Spark’ section to learn more about that process.

If the airbox wasn’t clogged and your spark plugs are in working order, fuel is the last of the holy trinity to examine.

The fuel pump is the most common fuel system component to fail on a Yamaha YZF 125.

You can troubleshoot your fuel pump by flicking your kill switch into a run as if you’re going to push the starter button.

Typically, when your lights flick on, you hear a whining noise like something is powering up before you start cranking the engine.

This whining noise is your fuel pump powering up.

  • If you don’t hear the whine at start up, the fuel pump isn’t getting power, likely because the pump itself is bad, especially if the electrical system is working OK everywhere else.
  • If you hear the whine at start up, turn the bike’s power off and back four or five times before you try starting it. This will prime the fuel pump; if the bike fires up after the fuel pump is primed, the culprit is likely a contaminated fuel injector.
  • If the bike doesn’t fire up after you’ve primed the pump multiple times, the pump itself is likely bad and needs to be replaced.

If none of the above have solved the issue, it’s always a good idea to check the battery.

2. Yamaha YZF R125 Won’t Idle/Won’t Stay Running

If your R125 won’t idle, stay running, or if it’s idling rough, the first thing to do is to check if your ECU is throwing any codes.

Depending on the year model, error codes should be accessible via the LED interface.

Still, you’ll have to confirm how to retrieve the code and what the code means with the service manual associated with your particular year model.

The most common reason a Yamaha YZF R125 has problems idling is that its valves are out of sync. Other culprits are timing chain adjustments, compression, fuel pump, and throttle body issues.

Valve adjustments are part of routine maintenance on the R125, as are inspecting and adjusting all the other components mentioned in the above paragraph.

Another common reason YZF R125s have throttle issues is when riders (or previous owners) try to bypass their ECU’s fuel mapping to get more power.

Tampering with the ECU can mess up the tuning of your bike’s engine and cause sensors to misread engine data, triggering inappropriate adjustments from your ECU.

3. Yamaha YZF R125 Clicks but Won’t Turn Over

If your Yamaha YZF R125 clicks when you press the starter button, but the bike won’t start, the problem is either a bad starter, a dead battery, or a seized engine.

If your R125’s battery is dead, your starter solenoid won’t get the juice it needs to magnetize; in this case, the clicking you hear is the solenoid trying to activate with what little power the relay is transferring from the dead battery.

If the solenoid itself is bad, or the starter motor, the clicking you’re hearing is the part attempting to function but failing.

If the starter relay is bad, it’s possible for it to make a clicking sound as it sheds the battery power.

That said, a bad relay usually won’t make a sound as it’s failing to relay power altogether.

And finally, if your engine is seized, the clicking you’ll hear is your starter motor trying to spin your flywheel against the impenetrable pressure of your seized motor.

4. Yamaha YZF R125 No Spark

The first thing to determine on an R125 with no spark is if there’s no spark and no power to the ignition coil or if there’s just no spark, but the coil is active.

If there’s no spark and also no power to the coil, the issue is likely with the wiring.

You’ll need to consult the wire harness diagram in the service manual associated with your bike to go through and test the wires integrated with the ignition coil.

Inspect the spark plug condition if there’s no spark, but your coil is active with power.

Inspecting a motorcycle spark plug is universal; more detailed instructions can be found in your service manual or even the owner’s manual–for now:

  • Check the color. You don’t want to see a scorched black spark plig anymore than you want to see a bleached-white plug.
  • Measure the gap. The gap should be between .6 and .8 mm, depending on the year model. Your owner’s manual will give you more specific instructions.

5. Yamaha YZF R125 Speedometer Not Working

To give a more accurate idea of what this might look like, let’s turn to a real-life YZF R125 owner testimony.

“The Speedometer was working fine just a few days ago, but after a rainy day, it stopped showing anything. The screen isn’t entirely black; there is still white background lighting.”

In most cases, the problem lies within the battery.

Sometimes, the battery just needs to be charged for some reason, and a quick trickle charger hook-up will have the speedo up and running in no time.

In other cases, the unlit speedometer is indicative of a more severe battery issue, like it’s dead or expired altogether.

If all other electronic features are working, no problem. The issue is likely not with the battery but with the connection exclusive to the speedometer’s wiring.

Inspect the wiring running into your speedometer, including the wiring behind the headlight bucket and its systems grounding.

It could also be a blown a fuse, especially if the Speedometer is on an isolated fuse circuit.

You’ll need to test your wiring and fuses with a multimeter per the instructions in the service manual of your particular year model.

6. Yamaha YZF R125 Dashboard Display Not Working

In some cases, the symptoms described above happen to the entire dashboard display, not just the speedometer.

In some cases, the gauges and displays are all fading, while in others, the gauges stop working completely.

If the entire dash display is fading in and out or stops working altogether, inspect the giant black plug behind the dash. This is the power for the whole display–if it’s loose or disconnected, or dirt or moisture has contaminated it, your Yamaha YZF R125’s dashboard display will have problems.

You’ll have to shove your arm in there to get to it, but it could be an easy fix. If it’s loose or disconnected, make sure it’s clean and plug it back in.

Clean it with some Yamaha-approved electronic-safe spray cleaner if it’s contaminated with dirt or water before reattaching it.

If it’s not the plug, move on to investigating the fuses and battery, as mentioned in the section above. 

7. Yamaha YZF R125 Headlights Not Working

If your Yamaha YZF R125’s headlights aren’t working, start by replacing the bulb and checking the fuse associated with its circuit. If the headlight fuse is blown, replacing it should do the trick.

If you’re frequently blowing headlight fuses, chances are there’s a short or fray in your headlight’s wiring.

Finally, the YZF R125 has connectors in the wiring loom on the same side as the low headlight beam.

  • Follow the loom down to a rubber component that’s zip-tied together; it should have the loom plugs plugged into it.
  • Unplug the plugs one at a time, give them a blow, clean out any debris with Yamaha-suggested, electronic-safe spray cleaner and plug them back in.

8. Yamaha YZF R125 Turn Signals and Indicator Not Working

If the turn signals aren’t working by themselves, start by inspecting the bulbs, fuses, power cabling, and wiring associated with the turn signal’s circuitry, especially if the signal indicator in your dash display is still working.

However, if the dash display’s turn signal indicator is failing to light up in addition to your turn signals not working, the problem lies within the turn signals switch. It’s likely a wiring issue, corrosion or wear and tear.

Still, if the turn signal switch fails, you’ll have to replace the whole switch unit.

9. Yamaha YZF R125 Keeps Cutting Out

If your Yamaha YZF sputters and then shuts off, always start by checking for loose battery terminals. Then, charge your battery for an hour and test its voltage with a multimeter or a voltmeter.

  • The battery voltage should rest at 12.8 volts, rising to 14.5 volts around 5,000RPMs (consult the owner’s manual for your year model R125 to confirm these readings for your particular bike).
  • Next, test your charging system. If your stator and Regulator Rectifier are all good, check your wiring–you may have a loose connection in the Fuel Injection’s electrical system.
  • Finally, inspect your throttle position sensor, and speed control solenoid.

If that doesn’t pinpoint the issue behind a YZF R125 engine that keeps cutting out, test the voltage on your Ignition bus, as this is the component that sources the power for all electronics once the bike flips on.

Finally, check your air intake and fuel injection systems aren’t clogged or contaminated.

Pros and Cons


  • One of the highest-performing small-displacement 4-strokes available.
  • Reliable and dependable
  • Long-lasting
  • Affordable price.
  • Affordable maintenance and ownership costs
  • Boasts Yamaha’s signature racing aesthetic in a small package. 
  • Fun to ride


  • Small engine size means serious sport riders will outgrow it quickly
  • As a popular choice for beginners, used R125’s change hands often
  • Intricate electronic display – regular inspection required

What Do the Reviews Say?

“The outgoing Yamaha YZF R125 was already a fantastic introduction to motorcycling, winning MCN’s 2018 sports 125 group test.

For 2019, Yamaha made it even better, with a purposeful new face, better engine, and class-leading handling to boot. It subsequently went on to win our Best 125cc Award in the same year.

With an 825mm seat height, the European-built bike will favor the taller rider; however, it remained perfectly manageable for this 5′ 6″ tester.

With more mid-range, no longer are you constantly chasing the higher RPMs to keep up with the traffic and out in the twisties. The improved ergonomics, wider rear tire, and boosted top-end make it a pleasure to chuck around.

Ever since Yamaha launched their R-series-styled entry-level sports bike a decade ago, it’s been at the top of the sales charts, often to be spotted at McDonald’s drive-throughs.

In November 2020, Yamaha announced the YZF R125 would now pass Euro5 emissions standards. “

Source: https://www.motorcyclenews.com/bike-reviews/yamaha/yzf-r125/2019/

What’s the Resale Value of a Yamaha YZF R125?


Related: 11 Common Problems With the Yamaha R6 (Solution Guide)

What Are Some Alternatives to the Yamaha YZF R125?

Make/ModelBase MSRP
Honda CB125R$5,585
Yamaha MT-125$4,000
Honda Monkey$4,199
Suzuki GSX-R125$6,431
KTM Duke 125$3,000


  • Michael Ta Nous

    I've been weaving words into stories since my early scribbling days, and my journey in the world of motorcycles and their communities spans almost two decades. Living with a talented motorcycle mechanic as a roommate, our garage transformed into a vibrant workshop where I absorbed the intricacies of...