Friday, 28 December 2012

Yamaha Circuit Magazine: DT Range

Text from Yamaha Circuit Magazine, from 1977, Issue 4, detailing the 1978 Yamaha DT range:

You can’t really call the Yamaha DT400 "a wolf in sheep‘s clothing" for the bike is one of the toughest-looking on/off road machines ever built. Even so, the description almost fits because the sleek, stylish lines of the DT400 give no hint of the power available from the big two-stroke single.
Fully at home on the street, with the five speed transmission and 29bbp motor giving a more than respectable high-speed cruising ability, the DT 400 comes equipped with all the luxuries of Life. Turn indicators, powerful headlamp. deep, comfortable dual seat, passenger footrests and speedometer / tachometer panel angled at 25 degrees towards the rider for easy vision.
Despite all of these niceties, a single glance at the DT400 reveals that it was destined to do something more than provide transportation to the office (though it would function quite competently in that role).
The monoshock chassis is a direct development of the unit used by Heikki Mikkola to win the 1977 World Championship and the 400cc motor bears a great deal of similarities to the  Championship-winning machine.
The off-road performance capabilities of the DT400 rank on a par with many pure moto cross racing machines and yet the big Torque Induction two-stroke is flexible enough to ride as a trials-type machine!
The reed valve induction aids in this respect and Yamaha Autolube oiling system plus Capacitor Discharge Ignition also combine to make the DT400 unit the kind of reliable power unit that you need if you are going to embark on the kind of long distance cross-country expedition that the big Yamaha seems to invite.
The Yamaha DT400 is meant for the kind of motorcyclist who enjoys his freedom ... the freedom to ride the wide open spaces at speed. But it also gives that motorcyclist a second choice ... a powerful bike for road cruising while flexible enough for commuting.
It is the absolute essence of the dual-purpose machine: capable of completing the International Six Days Trial on the one hand while happily dealing with six days commuting on the other! 
It's not uncomplimentary to suggest that Yamaha's DT250 Enduro machine sets a double standard ... especially when that double standard is the best possible compromise between the demands of street and off-road riding! In each of these areas the DT250 sets riding standards that other manufacturers can only hope to emulate, The superb Yamaha DT-Series power unit has been the subject of constant improvement and development since it first appeared a decade ago. Now it represents the ultimate state of the art in the attempt to design a power unit that will perform as well on the open road as it does on the moto-cross track.
Versions of this have powered Yamaha moto-cross machines to World and National Championships and the latest DT250 features another direct development from the racing scene ... the monoshock cantilever chassis. Proven both in moto-cross and road racing, the monoshock chassis revolutionised the world of suspension development when Yamaha introduced it five years ago. And Yamaha is still the only major manufacturer to utilise the cantilever frame for a volume production machine.
In every respect, the DT250 represents the pinnacle of "dual-purpose machine" development. It has everything that the serious off-road rider needs, including such refinements as unbreakable plastic front mudguards, re-settable trip meter and speedometer for the enduro enthusiasts, a chain tensioner and rubber boots on the front forks to keep out the water and dust.
On top of all this, the 23bhp, five-speed power unit and lighting equipment that meets all Government regulations (it has turn signals too) mean that the DT250 is more-than-respectable performer on the street.

The design of lightweight enduro machines has improved immeasurably over the past few years, with more and more manufacturers realising that not every trail rider wants to manhandle either the weight or the horsepower of the bigger machines on the tough trails.
Yamaha has always offered a top-quality lightweight in its dual purpose Enduro range but there's no doubt that the new DT125MX is more than a match for any comparative machine. It follows the big bikes in the Yamaha DT range in having the monocross suspension chassis that Yamaha designed for its World Championship · winning moto-cross racers. Now that competition technology has been put to work on an Enduro lightweight with staggering results.
Both in the chassis design and in its basic engine specification, the Yamaha DT125MX bears a close relationship to the Yamaha 125cc motocross racers that took Dutchman, Gerard Rond, to Grand Prix wins this year and which earned American National Championships for Bob Hannah and Broc Glover in the past two successive seasons.
This race-breeding is evident in the performance and the handling of the DT125MX ... a machine that is unique in the Enduro field.
It’s a tough trail lightweight that still has full street equipment making it capable of true double duty as a ride-to-work bike during the week and a really effective off-road lightweight whenever the getaway urge hits.
The engine of the DT125MX is based so closely on the engine of the moto cross YZ125 that it even looks the same, with heat dispersant matt black finish, alloy deep-finned head and cylinder barrel. The motor features a racing piston plus competition transfer porting. A high-grade steel crankshaft runs in roller bearings and drives through a multi-plate clutch to the six-speed gearbox.
It is all of this combined with reed valve torque induction that enables the engine of the DT125MX to produce true competition performance with street tractability.
Just like the rest of the famous Yamaha DT Enduro range of dual purpose street/trail bikes, the new DT50 is equally at home on city streets or out in the rough country.
Only difference between the DT50 and its bigger  brothers. as far as capabilities go, is its lack of cubic inches ... and to those riders whose preference is towards lightweight machines, that won't matter a bit.
The DT50 is a genuine endure machine on a small scale; a great little street bike that can carry you way across the city to work or out on the country lanes - but still a bike with true off-road capability.
Sharing the same tough little four-speed, Torque Induction engine as the TY50 trials machine, the Enduro-styled DT50 features a large capacity 6 Litre tank (plus separate oil tank for the Autolube engine unit), braced handlebars and enduro mudguards.
The high level exhaust pipe with heat shield completes the sporting look of this Yamaha ultra-lightweight especially designed with a dual-purpose role in mind. 

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