The long-running Yamaha DT 125 motorcycle is an attractive option for anyone looking to buy a no-frills, trusty offroad or trail bike.
Compared to modern sportbikes, the DT 125 will give you fewer headaches.
However, these bikes have some problems which we will discuss in this article.
Based on our analysis of multiple customer complaints, here are the most common problems associated with Yamaha DT 125 models:
1. Erratic Engine Performance
If there are issues affecting the engine, the bike’s performance will suffer.
Some Yamaha DT, 1265 model owners, have made several complaints revolving around the engine.
The most prominent of these problems is the engine-stalling problem. Also described as the engine “cutting out,” this issue can make for frustrating riding experience.
When you start your bike, you expect it to run flawlessly for the duration of your trip. But this isn’t always the case, particularly for some owners of the DT 125 model. According to affected users, the engine often acts erratically while they are riding.
In some cases, the engine may suddenly lose power and stall abruptly.
Worse, the engine may seize and cause the back wheel to lock up.
This, too, will cause your bike to stall on the road. You would even be lucky not to lose control in such a situation. We must, however, point out that the engine-seizing problem isn’t widespread on the DT 125 bikes.
A bike with stalling issues is never good for anyone, as it puts the rider at risk of a crash or collision.
Imagine riding on the highway, with cars and trucks zooming past, and your bike cuts out in the middle of the road. You easily could be rear-ended by an oncoming vehicle and suffer extensive injuries in the ensuing mishap.
Stalling isn’t the only engine problem on these models.
On occasions, the engine on the Yamaha D125 may ‘misfire.’
Symptoms of Misfiring Engine:
Here are some symptoms of a misfiring engine:
- The bike may vibrate/shake excessively while riding.
- You may feel some jerking or lurching when you try to accelerate, i.e., switch to higher gears.
- The bike hesitates on acceleration or loses power.
Here are some possible causes for the stalling problem on DT 125 models:
- Fouled spark plugs
- Blocked fuel breather
- Clogged fuel filters
- Faulty carburetors
- Faulty oil pump
Causes of Engine Misfiring:
Here are some possible reasons for the engine misfiring problem:
- Bad ignition coil
- Leaky intake manifolds
- Faulty fuel injectors
2. Problem with Transmission
The transmission is directly involved with the bike’s acceleration; hence, any problem with it will likely affect a bike’s speed.
This is what happens with some Yamaha DT 125 bikes.
These users report that they often experience problems while trying to switch gears.
Here are the most common transmission-related problems on the Yamaha DT 125:
– Bike Won’t Rev Past a Specific Limit:
In this case, the bike’s RPMs do not increase beyond a certain range.
For example, a particular DT 125 owner complained his bike almost never revved past 5000-7000 RPMs.
Another customer faced with the same problem reported that his bike’s RPMs never increased beyond 5000 RPMs.
The number varies across different users, but the problem remains the same: these bikes are not revving properly. This problem poses significant risks, especially as you won’t be able to increase the bike’s speed.
– The Bike is Stuck in Gear:
While this issue is similar to the aforementioned problem, they differ in some respects.
The first problem makes the bike unable to rev past some limit. This involves the transmission is stuck in a particular gear.
When you change gear, the transmission has to disengage briefly and thereafter, go into the selected gear.
If the transmission cannot disengage, then you won’t be able to shift. This problem may occur while you’re just starting or while you’re riding.
Either way, you won’t be able to increase or decrease your bike’s speed.
Here are some possible causes for this problem:
- Low transmission fluid
- Faulty clutch cables or linkage
- Faulty gearbox/transmission
- Faulty shift pedal
- Clutch drag
- Faulty clutch lever
3. Exhaust Manifold Rattling
The exhaust manifold collects exhaust gases from the engine’s cylinders for dissipation.
From reports, the exhaust manifold of the affected bikes makes a rattling or ticking noise.
These noises can be annoying and nerve-wracking and may make your ride very uncomfortable.
Diagnoses seem to suggest that the bolts securing the exhaust manifold may loosen.
Should this happen, the exhaust manifold will start making those rattling/ticking noises.
Other potential causes include cracks in the manifold or gaps in the manifold seal.
Any of these things may force your bike to make ticking or rattling sounds.
Check if the manifold bolts are not loose.
If they are loose, some DIY wrenching work should be enough to tighten the nuts and stop the rattling.
Inspect the exhaust manifold area for any signs of cracks or holes, especially if the exhaust manifold is old. Do the inspection when the motorcycle is cold; you may see/feel steam or gas coming out of the holes.
If the crack/hole isn’t particularly large, you may seal it with a sealant.
However, if the hole is large, you would be better off replacing the exhaust manifold.
4. Rough Idling Issues
Have you tried warming up your bike, only for it to launch into a series of wild revs?
You might also have noticed the bike shaking or vibrating excessively. Well, that’s what motorcycle enthusiasts refer to as “rough idling,” and it affects some DT 125 motorcycles.
While you’re idling, your engine should have low revs, ideally, between 700 RPMs to 1000 RPMs.
Anything above this is called a “high idle” (another term for rough idling). High idles are not only annoying but can be dangerous for you and your motorcycle.
What causes rough idling on motorcycles? A motorcycle idles high when it gets excess air-fuel mixture while in neutral or a low-speed position.
The greater combustion forces the pistons and crankshaft to move faster, which may explain the shaking and vibration.
Another cause for high idles on motorcycles is a badly adjusted idle screw. This component prevents the throttle valves from closing fully and controls the idle level.
You can turn the idle screw in or out to increase or decrease the bike’s idle speed. If you turn the idle screw too high, the idle speed will also remain at a high level.
Some also suggest a bad crank seal may cause the serious, rough idle problem. A symptom of a failing crank seal is unusually high RPMs.
The bike will rev normally at first, but as it gets warm, it will start revving high. Sometimes, the revs may eventually come down; in other cases, the bike sticks at high revs.
Other causes include an out-of-place throttle handle screw, bad throttle spring, or sticky throttle/throttle cable.
Ensure your throttle and throttle cable are in good condition always.
Don’t allow grime and dirt buildup in these components; otherwise, they could stick. If this happens, the throttle can be stuck at a high idle position, leading to some rough idling on your bike.
Use the choke to control how much fuel your bike gets while idling.
Adjust the idle screw to change the idle speed of your bike.
The service manual comes with a recommended idle level; we suggest you follow it.
General Pros and Cons of the Yamaha DT125
The following are some of the Yamaha DT125’s top-selling points and problems:
Pros of Yamaha DT125
Here are some of the pros of the Yamaha DT125:
1. High Build Quality:
The DT 125 bikes have been around for literally forever.
This has given Yamaha the time needed to work out the bugs on these motorcycles.
Barring a few problems, DT 125s are extremely durable bikes.
Moreover, the lack of extra components means there’re fewer chances of something breaking down.
2. Offers Great Value for Money:
The DT 125 is a low-cost bike that will prove attractive to any budget-conscious buyer.
Besides, it is cheap to insure and maintain and represents good value for anyone. Spare parts are widely available and are inexpensive.
Add to the fact that these bikes are extremely easy to service, and you understand why the DT 125 is a good investment.
3. Beginner Friendly:
Hardly any other bike screams “novice-friendly” as much as the DT 125.
Thanks to low power output, even newly licensed teenagers will find this bike easy to ride.
Wide bars also make it easy to maneuver for beginner riders.
Cons of Yamaha DT125
The following are some drawbacks of the DT125:
- Erratic Engine Performance
- Problem with Transmission
- Exhaust Manifold Rattling
- Rough Idling Issues
What Do The Reviews Say?
“Tall, upright and commanding, the Yamaha DT 125X is perfect for town riding and twisties. The long-travel suspension absorbs bumps while good, firm brakes will safely bring you to a halt. The handling’s the best bit, though: throw the motorcycle around, and it’ll respond brilliantly.”
“The evergreen Yamaha DT 125 continues to offer new riders an enjoyable route to life on two wheels…While that heady 14bhp may seem impressive to begin with, it won’t take long to outgrow.”
What’s The Resale Value On the Yamaha DT125?
Note: You may have to import these bikes into the United States.