Cantilever suspension for new Yamaha DT250

Press, 24 February 1977, Page 9

Cantilever suspension for new Yamaha DT250

By

ROD DEW

Gimmicks undoubtedly help to sell motor-cycles in a market which contains a large number of young and impressionable people. But it would be very wrong to put the remarkably efficient mono-shock or cantilever suspension of the new DT2SOD Yamaha trail bike in this category. Yamaha’s moto • cross machines have been equipped with the cantilever suspension for several years with obvious handling benefits to their riders. The system made it easier to provide for greater suspension movement without impairing the tracking qualities of the traditional twin shock absorbers.

Right from the start it has been obvious that the cantilever suspension would sooner or later be incorporated in the standard trail bike range and the only surprising thing is that Yamaha took so long to do this. The DT2SOD, and its bigger brother, the DT4OO, which have only recently been released on the New Zealand market, are the first bikes to reach this country for general consumption with the new suspension. A few hours on one of the new DT2SOD machines, borrowed from Tommy’s Yamaha, left no doubt that the new suspension works admirably. But it would be incorrect to suggest that this is the greatest thing since sliced bread. For normal going, an' average rider would probably notice very little difference. It is only when a rider extends himself a little in off-road conditions that the greater movement of the suspension is appreciated. Because of this, the bike is the most serious off-road mount yet produced by Yamaha. For a rider dedicated to the wilds, it is ideal. Where the compromise between road and trail has previously been in favour of the road, it is quite the opposite with this machine. Not that the Yamaha is out of its environment on the road. It could be used

very adequately as a commuter mount. It has excellent acceleration and a turn of speed which will keep it ahead of most, four-wheel traffic. But with severe bend-swinging on the tarmac, there is a sense of insecurity.

This is partly a result of the trials tyres fitted as standard but mainly because of the increased seat height of the machine in comparison with previous models. The new suspension gives a movement of more than seven inches at the rear and this cannot be provided without a loss in some other quality.

In the Yamaha’s case, the seating position is now really too high for comfort —a Tailing (if you could call it that) it shares with rival makes also searching

for more suspension movement. I found it quite difficult to swing a leg across the Yamaha and I am 6ft tall. My aging joints might not be what they once were but a smaller rider would clearly have some problems becoming accustomed to this. And once aboard, it is a rea] stretch to- put both feet on the ground. But, as I said before, this is a serious off-road mount —an obvious spin-off of the moto-cross racing bikes. It is a lot more than just a road tourer with a singlecylinder engine and plenty of ground clearance. The mono-shock system itself is outstanding. The nitrogen - fluid shock is situated under the seat and can be very easily tuned to the individual weight of the rider. A special tool is provided and the task is not one which needs a specialised mechanic. Surprisingly, the seat is bolted in place and two of these have to be removed before the seat can be lifted off and the mono-shock unit reached.

There is nothing else under the seat apart from the shock absorber and once this is adjusted there is no reason for lifting the seat. It is still a pity that there is no storage space left under the seat because this has proved very useful on earlier models.

The power unit, with its radial finning, is similar to that used for earlier machines and has a similar performance. It might be my imagination, but the low speed “grunt” does not appear to be quite as good, although the performance in the upper speed range seems much improved. This is another aspect which appears to emphasise the sporting side of the machine.

However, the specifications of the engine remain unchanged. It is a singlecylinder unit with seven ports and torque induction. Its actual capacity is 246 cu cm with a bore and stroke of 70 x 64mm. The maximum power is not publicised in the hand-out material but is probably

around 21 brake horsepower. It is a sound and solid unit which is not lacking in performance. The test engine was running a little rich and was happiest when under severe load. Idling or pottering along it was inclined to run a little unevenly. This could easily be changed by a different tuning emphasis.

The Yamaha incorporates a number of other advances apart from the increased travel for the front and rear suspension. The wheel rims are now aluminium instead of steel and the rear indicator lights are mounted in rubber. It has been suggested that it is impossible to break these in a fall and I am inclined to agree. It is just about possible to tie them in a knot without damage.

This is an excellent move in view of the new legislation making turning indicators compulsory on all bikes used on the road. Generous use is also made of flexible plastic. The front and rear mudguards are both plastic and in new condition, unbreakable. How they will react after a few years in the sunshine remains to be seen. No doubt they are easily replaceable, anyhow. The Yamaha has a competition type fuel cap with rubber air hose clipped to the handlebars. This must also meet with widespread approval, especially by those riders who have found themselves staring at an empty fuel tank after a minor fall miles from anywhere.

The rear wheel has a quick release system which is most impressive. A snail cam is used to maintain chain tension instead of the old nut and bolt arrangement.

The five-speed gearbox is excellent, high speed changes being possible with or without the clutch. A difficulty locating neutral once stopped could be put down to the stiffness of a new gearbox. One thing I must criticise is the paint work. Years ago, Japanese manu-

facturers appeared obsessed with chromium plating. Now, Yamaha at least, appears to have gone overboard for black paint. Everything is painted black except the wheel rims, fuel tank, body panels and handlebars. The engine, frame and even the wheel hubs containing the brakes are painted black. I would imagine that this could look very shabby indeed after a few years of use. Polished aluminium would be a lot easier to keep clean, especially in the engine “compartment.” This, obviously, is a fad of fashion and perhaps I am being old fashioned about it. But this certainly cannot detract from what is a truly outstanding trailenduro bike. The drum brakes, for example, are among the best I have experienced on a trail machine. They are progressive, efficient and do not fade easily. They are also dust proof and water proof. Even by road standards, they are much more than adequate.

A serious off-road rider would have to go a long way to find a better machine on which to blast off into the wide blue yonder. It represents a major step forward in serious trail bike design and, in most aspects, exceeds expectations. In New Zealand, it retails for $1699.