Yamaha DT125 Specs and Review

Inspired by a reputable line of ’60s “scramblers,” the Yamaha DT 125 is among the Japanese manufacturer’s longest-standing product lines. This two-wheeled machine may not be as powerful as 250-cc dirt bikes. But make no mistake – its competencies come second to none. More than its Enduro nomenclature, there are lots more to discover about this 125-cc wheeler – as you will soon find out in this guide.

Produced from 1974 to 2008, the Yamaha DT125 is considered an excellent learner motorcycle by many off-roaders and enthusiasts. Featuring aggressive Enduro styling, hydraulic disc brakes, and a monocross rear suspension, the bike performs excellently on the road and in the dirt.

Some riders (and reviews) regard the capabilities of the motorcycle as a compromise. But for those who have put their leg over this sleek ride, they find the reverse true. The Yamaha DT 125 never fails to deliver on dependability and performance – whether as a trusty commuter or an in-training motorcycle.

Blue Yamaha DT125R Bike

About Yamaha DT 125

The Yamaha DT 125 is a motorcycle produced by Yamaha, which traces back to 1968 when Yamaha introduced the AT-1 Enduro 125. The model designation “DT” indicates the bike is an off-road styled 2-stroke machine. The bike first launched in North America in 1974 as the DT125A and had a cradle-style tubular steel frame, raised exhaust, universal knobby tires, and high ground clearance characteristic of most Enduro motorcycles. Its entry into the U.S. market began with the 1975 Yamaha DT 125 until the DT125H in 1981. In non-U.S. regions, it continued to be sold until 2008.

Updates & Restyles

During its production, the Yamaha DT 125 received multiple updates and restyles, some of which were done only for specific markets. 1977 saw the introduction of a mono-shock rear swingarm or monocross suspension (a.k.a. MX). In 1984, the electrical components upgraded from 6V to 12V, and YPVS (Yamaha Power Valve System) was added. During the same year, the front drum brake was converted to a hydraulically operated disc, and the DT 125LC was fitted with a rising-rate rear suspension.

1987 saw the completion of its brake system overhaul when Yamaha offered the DT125R series that swapped out stock drums with a rear disc brake. And thanks to evolutionary changes like this, lots of DT 125 parts like the cylinder, head, piston, rings, air box, and exhaust (view on Amazon) were easily interchangeable with another Yamaha bike – the DT 175. As if its past restyles were not enough, the series released a road version marketed as the DT 125 X in the early 2000s, which many owners say is a dream to ride.

Yamaha DT 125 Specs & Features (1988 vs. 2005 Models)

Engine

The main differences between these model years are the 2-mm increase in carb size, bore-stroke ratio, and compression ratio variances. While they are quite negligible, they increase speed rating and power output up to 12.92 kW (17.33 hp) @ 7,000 RPM per Wikipedia. Furthermore, the DT 125 initially had an air-cooled engine. But this was restyled to a liquid-cooled power mill with the release of the 1982 DT125LC onward.

1988 – 2002 Yamaha DT125R 2005 Yamaha DT125RE / DT125X
Engine Type 2-stroke
Cylinder Arrangement Reed valve, forward-inclined single-cylinder
Carburetion System Carburetor, Mikuni VM26SS x 1;
Mikuni TM28SS x 1 – ’99 onward
Carburetor, Mikuni TM28-92 x 1
Engine Cooling Liquid cooling
Engine Fuel Unleaded gasoline w/ at least RON 91 rating, containing < 5% MTBE (Methyl Tertiary Butyl Ether), < 10% ethanol, or < 5% methanol
Fuel Capacity 10 L/2.6 US gal (reserve – 1.8 L/0.48 US gal)
Bore x Stroke Ratio 56.4 x 50 mm (2.22 x 1.97 in);
56 x 50.7 mm (2.20 x 2.00 in) – ’89 onward
56 x 50.7 mm (2.20 x 2.00 in)
Compression Ratio 6.8:1 6.7:1
Displacement 124 cm³ / 7.6 in³
Horsepower 12 – 14 hp (8.9 – 10.2 kW) @ 7,000 RPM 14.7 hp (11 kW) @ 8,000 RPM
Maximum Torque 14 Nm (1.4 kgf-m, 10.5 ft-lb) @ 7000 RPM 13 Nm (1.3 kgf-m, 9.6 ft-lb) @ 8,000 RPM
Top Speed 68 mph (109 km/h) – advertised 75 – 80 mph (120.7 – 128.7 km/h) – owner’s claim 95 mph (153 km/h) – modded
Air Filtration Wet foam element
Lubrication Separate lubrication (Yamaha Autolube)
Engine Oil & Quantity 1.3 L/ US gal; 0.75 L/0.79 US quarts (transmission – change);
0.80 L/0.84 US quarts (transmission – overhaul)
SAE 10W-30 (transmission), Yamaha 2T (engine) 2-stroke oil or its equivalent
Alternatives: same-viscosity lube w/ API grade SJ+ meeting JASO MA standards

Something most notable about the bike is its lubrication system. Instead of the usual dry/wet sump types, the bike has an autolube oil container discreetly concealed behind the left-side panel. This oil injection system controlled the amount of lube going into the engine depending on throttle load, reducing oil usage and preventing the spark plug from fouling in the process.

Drivetrain

The DT125 uses a 6-speed manual transmission and a five-plate wet clutch system. Helical gears and 428V O-ring chain (view on Amazon), coupled with a ball and taper roller bearing steering system, lends to the two-wheeler’s predictable handling and ease of operation, regardless of the terrain. The bike’s top two gears offer overdrive. Mechanics say that adjusting the gearing to 49/15T on the road-legal version allows a rider to go beyond 55 mph.

1988 – 2002 Yamaha DT125R 2005 Yamaha DT125RE / DT125X
Steering System Ball and taper roller bearing
Clutch Wet multiple disc (left foot operation)
Transmission Type 6-speed constant mesh, return
Gearshift Pattern 1-down, 5-up
Final Drive #428V/DAIDO chain, 134 links (including joint) #428V2/DAIDO chain, 134 links (including joint)
Primary Reduction Ratio 3.227 (71/22)
Final Drive Ratio 2.235 (55/17) – ‘88; 3.118 (53/17) – CH; 3.563 (57/16) – ’89 onward 3.563 (57/16)
Transfer Gear Ratio Low – 2.833 (34/12)
2nd – 1.875 (30/16)
3rd – 1.412 (24/17)
4th – 1.143 (24/21)
5th – 0.957 (22/23)
Top – 0 .818 (18/22)

Ignition

Like most pre-’80s Yamaha bikes, the Yamaha DT 125 initially had a 6V wiring harness and an electronic CDI that brings the two-wheeler to life. The magnetically triggered ignition system enabled the dirt bike to have a quicker spark, which reduced the fouling of the plug caused by the oil and gas mixture in the engine’s combustion chamber. While the 6V-CDI combo was sufficient for the bike, it did not allow it to ride legally on the streets. So, the wiring harness was changed to 12V in 1984 and has remained that way since.

1988 – 2002 Yamaha DT125R 2005 Yamaha DT125RE / DT125X
Ignition Electronic CDI (Capacitor Discharge Ignition)
Ignition Timing 19° B.T.D.C @ 1,350 RPM – 3DB1;
17° B.T.D.C @ 1,350 RPM – 3NR1
17° B.T.D.C @ 1,500 RPM
Idle Speed 1,300 – 1,400 RPM 1,250 – 1,450 RPM
Spark Plug, Gap NGK BR9ES / NIPPON DENSO W27ESR-U, 0.7 – 0.8 mm (0.028 – 0.032 in) gap NGK BR8ES, 0.7 – 0.8 mm (0.028 – 0.032 in) gap
Tightening Torque 20 Nm (2.0 kgf-m, 14 lb-ft)
Generator Flywheel magneto A.C. magneto
Rated Output 13.3 – 15.3V @ 3,000 RPM 14V 170 W @ 5,000 RPM
Fuse (Main) 10 Amp 15 Amp
Starting System Kick & mesh type Electric starter
Battery 12V 3Ah/(10 HR) sealed, GM3-3B/FB3L-B formats 12V 6Ah/(10 HR) sealed, GT6B-3 format
Alternative: YTZ7S/YTX5L-BS formats
Battery Dimensions 98 x 56 x 106 mm (3.86 x 2.20 x 4.17 in) 114 x 71 x 106 mm (4.50 x 2.81 x 4.19 in) – GT6B-3/YTX5L-BS
113 x 70 x 105 mm (4.44 x 2.75 x 4.12 in) – YTZ7S

Tires & Brakes

Tubed front and rear tires mounted on wire-spoked, chromed steel rims remained as the factory tires throughout the early years of the DT 125. It was until the early 2000s that spoke wheels and Michelin/Pirelli tires were introduced on the then street-friendly and emissions-compliant bike. Front and rear brakes were initial drum types but upgraded to discs later on. While the brake system felt incredibly spot-on in the dirt, they did not have much bite on asphalt. This is where the knobby tires came in to make up for the lack of grip on-road.

1988 – 2002 Yamaha DT125R2005 Yamaha DT125RE / DT125X
Wheel CompositionWire-spoked, chromed steelSpoke
Front TireBridgestone TW25 2.75 x 21 4PR, tubedMichelin T63 80/90-21 48P or Pirelli Sport Demon 120/70-17 58H, tubed
Rear TireBridgestone TW44 4.10 x 18 4PR, tubedMichelin T63 110/80-18 58P or Pirelli Sport Demon 140/70-17 66H, tubed
Off-road/road air pressure (F/R)130 – 150 kPa (1.3 – 1.5 kgf/cm2, 18 – 22 psi) / 150 – 180 kPa (1.5 – 1.8 kgf/cm2, 22 – 26 psi)150 – 180 kPa (1.5 – 1.8 kgf/cm2, 22 – 26 psi) / 175 – 200 kPa (1.7 – 2.0 kgf/cm2, 25 – 29 psi)
Rim Size (F/R)1.60 × 21 / 1.85 × 181.60 × 21 / 1.85 × 18 – DT125RE;
3.00 x 17 / 3.50 x 17 – DT125X
Tread Depth Limit1 mm (0.04 in)1.6 mm (0.04 in)
Front Brake TypeHydraulically operated, 230-mm single disc brake (right hand operation)Hydraulically operated, 230-/298-mm single disc brake (right hand operation)
Rear Brake TypeHydraulically operated, 230-mm single disc brake (right foot operation)Hydraulically operated, 220-mm single disc brake (right foot operation)

Suspension

Early-year models of the DT125 had front forks and dual rear shocks. That changed in 1977 when the dirt bike was redesigned with a single-shock rear end – otherwise known as a monocross suspension (the same ones found on Yamaha YZ racers). This setup consisted of a cantilever-style swingarm and long de-carbon hydraulic shock running to the steering head. Not only did the redesigned suspension system make for a great image, but it also made for excellent absorption of dips and bumps. Furthermore, the nitrogen-fed gas shock reduced the likelihood of the suspension bottoming out.

1988 – 2002 Yamaha DT125R2005 Yamaha DT125RE / DT125X
Rake, Trail27.5°, 113 mm (4.45 in)27º, 107 mm (4.21 in) / 24.5°, 73.1 mm (2.88 in)
Turning Radius2.1 m (6.9 ft)2.1 m (6.9 ft) / 2 m (6.6 ft)
Ground Clearance315 mm (12.4 in)300 mm (11.8 in) / 271 mm (10.7 in)
Wheelbase1,415 mm (55.7 in)1,415 mm (55.7 in) / 1,396 mm (55 in)
Front Suspension Type, TravelTelescopic fork w/ oil-damped coilover shocks, 270 mm (10.6 in)Telescopic fork w/ oil-damped coilover shocks, 270 mm (10.6 in); 200 mm (7.87 in) – DT125X
Rear Suspension Type, TravelSwingarm (monocross suspension) w/ oil-damped gas shocks, 260 mm (10.2 in)Swingarm (link suspension) w/ oil-damped gas shocks, 260 mm (10.2 in); 230 mm (9.05 in) – DT125X

Dimensions & Capacities

Overall dimensions varied depending on the model year and region where the dirt bike was marketed. Units sold in Sweden and Finland were roughly two inches longer than those in North America. The DT125X was 12 inches wider and 17 pounds heavier than the rest of the models. Despite these variances, the payload capacity of the different bike models only differed by two kilograms.

1988 – 2002 Yamaha DT125R2005 Yamaha DT125RE / DT125X
Length2,160 mm (85 in); 2,250 mm (81.1 in) – SW/D/CH; 2,285 mm (82.4 in) – FI; 2,170 mm (85.4 in) – ’99 onward2,210 mm (87 in) / 2,139 mm (84.2 in)
Width830 mm (32.7 in)795 mm (31.3 in) / 1,121 mm (44.1 in)
Height1,255 mm (49.4 in)1,200 mm (47.2 in)
Seat Height (Unloaded)885 mm (34.8 in)900 mm (35.4 in) / 886 mm (34.9 in)
Curb Weight119 Kg (262 lbs); 127 Kg (219 lbs) – ’99 onward126 Kg (278 lbs) / 134 Kg (295 lbs)
Payload Capacity (F/R)47 Kg (104 lbs) / 134 Kg (295 lbs)178 – 180 Kg (392 – 396 lbs)

Exterior

It consists of a semi-double-cradle steel frame and plastic body panels in multiple color options. The saddle seat is long and can comfortably seat two riders if need be. High-clearance fenders provide mud and splash protection and allow taller tires to be mounted on the wheels. Earlier models sported an old-fashioned dash with an analog speedometer (view on Amazon), tachometer/trip meter, and a light grid for oil. The dash was later restyled to look more modern while retaining the same components. Other standard inclusions are handlebar and hand grips, a full lighting set, and a horn.

1988 – 2002 Yamaha DT125R 2005 Yamaha DT125RE / DT125X
Frame Semi double cradle
Body Material Plastic
Front/Rear Fender Flares Standard
Upper/Lower Fairing N/A
Chain Guards Standard
Fork Guards N/A
Skid Plate
Stand Type Side stand (no center stand)
License Plate N/A

Lighting

1988 – 2002 Yamaha DT125R 2005 Yamaha DT125RE / DT125X
Headlight 12V 45/40 W x 1 Halogen H4 bulb-type, 12V 60/55 W x 1
Parking Light/Stoplight 12V 4 W x 1 N/A
Brake/Taillight 12V 21/5 W x 1
Flasher Lights 12V 21 W x 4
Indicator Lights 12V 21 W (turn signal), 3.4 W (meter, auxiliary), 3 W (neutral, high-beam, oil, license, warning lamps) 12V 10 W (turn signal), 12V 3 W (oil, neutral, high-beam, low-beam, license), LED (meter)

Yamaha DT 125 Price

Based on Nada Guides collected data, the original list price of the Yamaha DT 125 was $825. This value moved up to the $6,249-$6,479 range in the final two years of production (at the time the DT125RE and DT125X were already introduced in the market). Resale pricing, on the other hand, falls between $730 and $2,925. Of the pre-owned DT125s, pre-1978 and Post-1988 models seem to keep their value best. Any other unit outside of these model years is sold for less than $900.

Yamaha DT 125 Pros and Cons

Blue Yamaha DT125 Bike

Despite its rock-solid nature and proven reliability, the DT 125 is far from being perfect. Here are some things to note should you choose to acquire this two-wheeler:

Pros:

  • Retro aesthetics
  • Big saddle seat providing riding comfort – sometimes, even for two riders
  • Straightforward bike with only the essentials
  • Monocross rear suspension lending to superb handling on bumps and ruts
  • Pleasant high-riding position with easy cruising control 
  • High-raise fenders providing much-needed mud and splash protection
  • Reduced maintenance due to simplicity of mechanical components
  • Tremendous aftermarket support and availability of affordable servicing

Cons:

  • No built-in storage at all
  • Brakes do not perform as well on pavement as in the dirt
  • May feel snatched at low RPMs, especially when caught in traffic
  • Not ideal for out-of-town or extended periods of riding
  • Instrumentation is incomplete – does not have a rev counter
  • Known to have the following issues – transmission problems, repeated stalling/misfiring, restricted revving, and rattling in the exhaust manifold

Although valid, issues with erratic engine performance and getting stuck in gear are mostly associated with the amount of care given to the motorcycle. Stalling, for instance, is often traced back to a fouled spark plug, which could indicate either an honest forgetfulness or willful neglect of periodic checks and maintenance. In like manner, the gears failing to disengage are often caused by worn clutch plates or a faulty clutch lever – which is usually a sign of the bike’s old age.

About Yamaha

Founded in 1887, Yamaha Motor Company Limited traces its humble beginnings back to music, manufacturing pianos and reed organs. The Yamaha DT 125 maker eventually entered the automotive industry by venturing into the production of motorcycles. Soon, it parted ways with its parent company in 1955 and has made huge strides in the manufacture of motorized vehicles since. The Japanese firm is known for its unrivaled water vehicle sales and for pioneering the ATV industry.

Conclusion – Yamaha DT 125 Review

Old-school dirt bikes like the DT 125 do not require a beastly supermoto to tread smoothly on- or off-road. Often, a no-frills bike works better in providing riders that memorable outdoor experience. With the DT125, fewer things can go wrong as it only has the essentials – which are all you will need to plow through mud and rocks or ride on tarmac with confidence. Whether you are commuting or enjoying the weekend with friends, you are guaranteed good acceleration and grip and unrelenting performance on this bike. Indeed, the Yamaha DT125 is a classic motorcycle that would be folly to miss!

Kris Peter

Adventure seeker and off-road enthusiast. I love the thrill of going off-road and taking on the elements.

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