Yamaha DT1

Image courtesy of Yamaha Motor Corp.

Although Yamaha claims to have produced the first mass produced on/off road bike (dual sport) with their DT Enduro, many manufacturers had already produced machines that could be used both on dirt and tarmac.

Historically, it was quite common for early motorcycle riders to use their machines during the week to commute to and from work, and then use the same bike at the weekends to do competitions (for example, riding in events such as Scrambles or trials).

A typical example of an earlier dual sport bike, albeit only slightly earlier than the Yamaha, is the Triumph Mountain Cub which became available in 1964.

High Sales Figures

But it was the Yamaha that changed the world of mass produced dual purpose motorcycles. The DT1 sold in incredible numbers—50,000 units per year incredible! Yamaha, along with their American distribution center, saw an opening in the market and produced a machine that not only was a perfect fit, the timing of its release was also perfect.

Buyers of the DT (code named YX047) found a motorcycle that was truly a dual sport bike. It was a capable street bike that could be ridden on trails and back woods with abandon. The simple layout and specification ensured a reliable machine too.

Over the years (variations were produced from 1967/8 with the DT1, to the 1979 DT250F). The DT 250 Yamaha was changed considerably during its production run which in many aspects reflected the trends in MX.

In the earlier years, Yamaha made a kit available for the serious off-road rider known as the GYT (Genuine Yamaha Tuning Kit).

By 1972/3 the exhaust system has been rerouted to pass over the cylinder head to the left side before winding back through the frame to exit on the right. The front fender (now plastic) was mounted under the triple clamp MX style.

The rear suspension had also been changed to incorporate additional damping oil in a remote reservoir.

In 1976, the DT received some cosmetic changes in the form of a reshaped fuel tank and a finish change to the crankcases which became flat black. But 1977 saw the biggest change to the DT range when a completely new model was introduced: the DT250D.

Mono Shock

A duplex cradle style frame was used on the new model, but the single biggest change from the old model was the incorporation of Yamaha’s famous rear mono shock suspension. Weight was trimmed from the bike by the use of aluminum rims. A redesigned fuel tank resembled the earlier bikes with its tapering section to the rear (again no doubt reflecting the MX lineage where riders often slid up the sloping tanks to add weight to the front of the bike).

The new machine weighed just 260 lbs (118 kgs) which combined with a reliable 21 hp engine and a five-speed gearbox gave the Yamaha a reasonable power to weight ratio.

Specification for the 1968/71 DT:

  • Engine: Piston ported 246-cc 2-stroke producing 18 hp at 6,000 rpm
  • Gearbox: Five speed
  • Ignition: Magneto with contact points and condenser
  • Suspension: F – telescopic forks, R – twin coil over shocks
  • Weight: 230 lbs (105 kgs)
  • Tires: F – 275 x 21, R – 400 x 18
  • GYT kit included: Modified cylinder and head, competition piston, a new carburetor and an expansion chamber

Today, the early Yamaha DT1s in excellent condition are worth around $4,200 (a considerable increase over last years value).

Further reading:

Suzuki TS Range

Dual Sport Classic Motorcycles