1973 Yamaha DT 125 Specifications

Name: 1973 Yamaha DT 125
Brand: Yamaha

Enduro / Off-Road • Specs last verified 13 July 2026

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1973 Yamaha DT 125 Overview

Yamaha DT 125 is an enduro / off-road motorcycle, displacing 123 cc. Power comes from a Two stroke, single cylinder engine, a compression ratio of 6.9:1. On the performance side, it delivers 12.9 kW @ 7000 rpm of peak power and 1.4 kgf-m @ 7000 rpm of torque. On the road, the 1973 DT 125 tips the scales at 125 kg and carries a 9.5-litre fuel tank. That's roughly 44.2 kg lighter than the average enduro / off-road motorcycle in our database. The full 1973 Yamaha DT 125 spec sheet below covers every technical detail, from suspension travel to tyre sizes.

1973 Yamaha DT 125 compared with other bikes in the Enduro / Off-Road category

We checked the recorded figures for the 1973 Yamaha DT 125 against up to 1434 bikes in the Enduro / Off-Road category in our database, counting each model once at the model year nearest to this one.

Only 54 of the other 1433 bikes in the Enduro / Off-Road category have a smaller engine displacement than the 123 cc of the DT 125.
With 103 W/kg, the DT 125 has the 45th lowest power-to-weight ratio of 434 bikes in the Enduro / Off-Road category, 57% below the category average of 239 W/kg.
Torque of 13.6 Nm is lower than that of 725 of the other 815 bikes in the Enduro / Off-Road category.
Narrowing the field to the 63 models within five model years of it, the engine displacement of 123 cc is smaller than that of 57 of the other 62.

Versus the 1972 model

The figures we track are unchanged from the 1972 model: peak power, peak torque, wet weight and displacement all match.

1973 DT 125 - Pros & Cons

Strengths

Strong power output: With 12.9 kW @ 7000 rpm and 1.4 kgf-m @ 7000 rpm of torque on tap, the DT 125 is no slouch for its class.

Considerations

Carburetor fuelling: Expect to spend more time keeping the carbs in tune, especially after long storage periods or a change in altitude.
Drum rear brake: Rear braking comes from a drum, not a disc - it does the job but won't match the feel or fade resistance of newer equivalents.
Modest fuel capacity: Range between stops is limited by the 9.5-litre tank - plan fuel stops accordingly on longer routes.
Chain final drive upkeep: Budget time for routine chain maintenance - it's cheap to replace but needs consistent attention to avoid premature sprocket wear.

Wear Points & Servicing Notes

Heat management in traffic

Because the DT 125 relies on airflow rather than a coolant jacket, expect noticeably more radiant heat at low speed and in traffic. It's inherent to air cooling, and ventilated gear largely offsets it.

Carburetor maintenance

Carburetors on the DT 125 need periodic attention - pilot jets and float needles are the first parts to gum up after the bike sits, and the first thing to check if idle or throttle response degrades.

Suspension condition on used examples

The DT 125's suspension runs Telescopic forks at the front. The rear uses Dual shocks. Fork-seal condition and rear linkage play are the two things worth checking before buying used.

Final drive maintenance

The DT 125 uses chain final drive, which is cheap to replace but needs regular cleaning, lubrication and tension checks to get a full service life out of the sprockets.

Low-speed handling

125 kg keeps the DT 125 easy to move around in tight spaces, car parks and on the stand alike.

DT 125 - Buying & Maintenance Guide

What to check before buying

Before handing over money for a used 1973 Yamaha DT 125 with its 123 cc enduro / off-road, cover the fundamentals: service book and oil change history, drivetrain wear, and any sign of oil weeping around the casings. This model runs chain final drive, so check chain slack and sprocket tooth profile specifically - a worn sprocket is a cheaper fix now than after it's chewed up the next chain. Now 53 years old, this enduro / off-road is as likely to show age-related wear (perished rubber, seized fasteners, degraded seals) as mileage-related wear. Cold-starting it yourself tells you a lot - a healthy DT 125 should catch quickly and settle into a smooth idle.

Oil and filter changes

Nothing protects the DT 125's 123 cc two stroke, single cylinder like disciplined oil changes - stay on the manufacturer's schedule (roughly every 6,000 km or annually). With a 6.9:1 compression ratio, running the octane grade specified in the manual matters more than on a lower-compression engine. Match the viscosity grade to what the owner's manual specifies, not what's cheapest.

Carburetor upkeep

Deposits in the carbs are the usual culprit behind poor running on a stored DT 125 - strip and clean the float bowls before the first start. Pilot jets clog first and get overlooked most, so make a point of checking them.

1973 Yamaha DT 125 - Frequently Asked Questions

What engine does the 1973 Yamaha DT 125 have?

The 1973 Yamaha DT 125 uses a Two stroke, single cylinder engine with 123 cc of displacement. It is air cooled.

How much does the 1973 Yamaha DT 125 weigh?

The 1973 Yamaha DT 125 weighs 125 kg. This is the manufacturer's wet figure.

How much power does the 1973 Yamaha DT 125 make?

The 1973 Yamaha DT 125 produces 12.9 kW @ 7000 rpm of power and 1.4 kgf-m @ 7000 rpm of torque. These are peak figures.

What is the fuel tank capacity of the 1973 Yamaha DT 125?

The 1973 Yamaha DT 125 has a 9.5-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 158-190 km between stops.

What brakes does the 1973 Yamaha DT 125 have?

The 1973 Yamaha DT 125 uses drum at the front and drum at the rear.

What tyre sizes does the 1973 Yamaha DT 125 use?

The 1973 Yamaha DT 125 runs 2.75-21 front and 3.50-18 rear tyres. A good selection of sport, touring and all-weather rubber is available in these sizes.

What gearbox does the 1973 Yamaha DT 125 have?

The 1973 Yamaha DT 125 is fitted with a 5 Speed transmission.

Yamaha DT 125 Spec Evolution

The Yamaha DT 125 was produced across 5 model years (1972-1978). The table below highlights the key specifications that changed across the production run - useful whether you are comparing years or tracking down a specific variant.

Specification	1972	1974	1976	1977	1978
Max Power	12.9 kW / 17.3 hp @ 7000 rpm	12.9 kW / 17.3 hp @ 7000 rpm	12.9 kW / 17.3 hp @ 7000 rpm	13 hp / 9.5 kW @ 7000 rpm	13 hp / 9.5 kW @ 7000 rpm
Engine Detail	Two stroke, single cylinder	Two stroke, single cylinder	Two stroke, single cylinder	Two stroke, single cylinder, reed-valve	Two stroke, single cylinder, reed-valve
Fuel Capacity	9.5 Litres / 2.5 US gal	9.5 Litres / 2.5 US gal	9.5 Litres / 2.5 US gal	6.8 Litres / 1.8 gal	6.8 Litres / 1.8 gal
Suspension - Rear	Dual shocks	Dual shocks	Dual shocks	Monocross	Monocross
Compression Ratio	6.9:1	6.9:1	6.9:1	7.2:1	7.2:1
Transmission / Drive	5 Speed	5 Speed	5 Speed	6 Speed	6 Speed
Fuel Induction	Mikuni TS28SS Carburetor	Mikuni TS28SS Carburettor	Mikuni TS28SS Carburettor	Single 24 mm Mikuni carburettor	Single 24 mm Mikuni carburettor
Max Torque	1.4 kgf-m / 10 lb-ft @ 7000 rpm	1.4 kgf-m / 10 lb-ft @ 7000 rpm	1.4 kgf-m / 10 lb-ft @ 7000 rpm	9.8 lb-ft @ 6,500 rpm	9.8 lb-ft @ 6,500 rpm

Key Specifications

Engine

Two stroke, single cylinder

Power

12.9 kW / 17.3 hp @ 7000 rpm

Torque

1.4 kgf-m / 10 lb-ft @ 7000 rpm

Top Speed

Not recorded

Weight

125 kg / 275.5 lbs

Fuel Capacity

9.5 Litres / 2.5 US gal

Full 1973 Yamaha DT 125 Specifications

Year 1973-74

Make Model Yamaha DT 125

Fuel Capacity 9.5 Litres / 2.5 US gal

Wet Weight 125 kg / 275.5 lbs

Max Power 12.9 kW / 17.3 hp @ 7000 rpm

Max Torque 1.4 kgf-m / 10 lb-ft @ 7000 rpm

Displacement 123 cc / 7.5 cu-in

Engine Detail Two stroke, single cylinder

Bore x Stroke 56 х 50 mm

Compression Ratio 6.9:1

Cooling System Air cooled

Fuel Induction Mikuni TS28SS Carburettor

Ignition Magneto

Starter kick

Final Drive Chain

Transmission / Drive 5 Speed

Suspension - Front Telescopic forks

Suspension - Rear Dual shocks

Brakes - Front Drum

Brakes - Rear Drum

Tyres - Front 2.75-21

Tyres - Rear 3.50-18

Specifications are compiled from manufacturer documentation and cross-referenced technical sources, and corrected on an ongoing basis. Spot an error? Let us know.

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