2004–2007 · Supermoto · Buyer's Guide
Two-Stroke Supermoto Razor
The DT 125 X keeps things gloriously simple. Its liquid-cooled 124 cc single is a genuine two-stroke, fed by the YPVS power valve, and it makes 15 hp that only wakes up when you keep it spinning near the top of the 6-speed box. The steel semi-double-cradle frame, 17-inch wheels, and 298 mm front disc give it a proper supermoto stance rather than a dressed-up trail bike. There is no rev counter and no fuel gauge. What you get instead is an honest, analog machine built around handling and the sharp bark of a smoking single.
On the road it rewards commitment. Short-shift it and nothing happens; wind it out and the little single sings. Its light weight and long-travel suspension make it a natural for chopping up back roads, though the tall 34.9 in seat asks for long legs. Ownership is where you pay your dues. Like any two-stroke it wants a top-end refresh if you ride it hard, the 2.8 gal tank keeps range short, and the steel frame and exhaust need cleaning to hold off rust. For a rider chasing pure, cheap fun, that trade is worth making.
Spec sheets don't ride bikes, but they set the baseline.
| Power | 15 hp (11 kW) @ 8,000 rpm |
|---|---|
| Torque | 10 lb-ft (13 Nm) @ 8,000 rpm |
| Displacement | 124 cc |
| Engine | Single-cylinder |
| Cooling | Liquid-cooled |
| Gearbox | 6-speed |
| Final drive | Chain |
| Fork | Telescopic |
| Front brake | 298 mm |
| Front tire | 120/70-17 |
| Rear tire | 140/70-17 |
| Front travel | 4.7 in (120 mm) |
| Rear travel | 7.9 in (200 mm) |
| Seat height | 34.9 in (886 mm) |
| Fuel capacity | 2.8 gal (10.7 L) |
Equipment check
Chassis
Swing a leg over and the height registers first. At 34.9 in the seat puts you high and commanding, wide bars in your hands, and the weight all but disappears when you lift the bike off the sidestand. Thumb the ignition and you catch the faint whir of the power valve running its check. Once you are moving, the two-stroke soundtrack is the whole event, a hollow ring-ding that hardens into a top-end rasp, with the fine buzz through the pegs and bars that comes with a small single. The riding position is roomy and upright, easy to weight from side to side, and the chassis stays chatty and honest underneath you. At real road pace it feels tiny and tossable, eager to change direction on the smallest input. It is a machine that makes 30 mph feel like an occasion.
This part isn't me in the saddle; it's the collective read I've built over years of listening to riders. Talk in the pits, ownership threads I keep tabs on, and notes people send me directly about living with the bike. Pointed at the DT 125 X, the picture holds steady across owners: an inexpensive, eager two-stroke riders warm to, with a few flaws they accommodate.
Two strands carry most of the goodwill. First is affordability: riders point to rugged, uncomplicated hardware they can wrench on at home, low parts prices, and no fragile electronics. Second is the front end, praised as light and precise, happy to tip into a corner on the smallest input yet steady through faster curves. The liquid-cooled two-stroke completes the appeal, gentle for a novice but keen to climb the revs once you lean on it.
The criticisms run milder and more scattered. Some riders mention a hesitation in the mid-range that a fueling change tidies up. A handful want the plain panel to show engine speed and fuel instead of leaving them to guess. Seat height draws objections as the miles add up, and the poorly placed choke leaves a cold motor cutting out until you stop and reset it by hand.
Stator / source coil failures
Some owners report repeated failure of the stator source coil, leading to loss of spark. Often traced to a faulty voltage regulator/rectifier or a modified wiring harness that lets excess current fry the coil.
Power valve sticking
The YPVS power valve can become stuck open if it is tampered with or carbon builds up. A tell‑tale sign is the absence of the whirring noise when the ignition is turned on; stuck valves degrade bottom‑end power.
Engine top‑end wear
Like all two‑strokes, piston, rings and bore will eventually need attention. Hard‑ridden examples may require a top‑end refresh earlier than expected; the silver lining is that the engine is simple to work on.
Corrosion‑prone frame and exhaust
Paint chips easily on the steel frame and swingarm, leading to surface rust; the standard expansion chamber also rusts, especially near the mounting bracket. Regular cleaning and ACF‑50 treatment are advised.
Where this Yamaha DT 125 X pulls ahead of — or falls behind — its rivals on the numbers, and the typical bike in its class on character.
Power
Torque
Displacement
Seat height
Forget spec-sheet bragging. Here's who the DT 125 X is actually built for.
For your skill and those Angeles Crest hairpins this is a featherweight toy, not a fast bike. It rewards smooth lines and clean corner speed, but on the straights faster traffic just rides away from you.
Made for Angeles Crest Highway · Coronado Trail / US 191 · Highway 1 / Big Sur
It is a riot whittling through the Twisted Sisters at a playful pace, but the small 2.8 gal tank and modest speed make longer Hill Country runs a stretch. Best kept as a local backroad blast.
Made for Austin / Texas Hill Country · Twisted Sisters · Austin / Handbuilt Motorcycle Show
Photogenic, analog, and a hoot on Skyline's tight stuff. If you want screens, tech, or an easy commute, look elsewhere; this is a raw two-stroke for the pure joy of the ride.
Made for Bay Area Ridge Roads · San Francisco / Bay Area · Skyline Boulevard / Alice's Restaurant
If this one isn't quite the fit, these are the bikes worth riding back-to-back against it.
Any price note compares both bikes at the same age — the youngest age both have on the used market — against this Yamaha DT 125 X. “cheaper/pricier” is what that bike costs second-hand, not how worn it is.
