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Yamaha RT-1 360
We are privileged to test this month
the actual machine, the Yamaha RT1, which won the motorcycle section of the Roof
of Africa Rally in September. Ridden by Roy Linley of the Nomads Club of Cape
Town, this Enduro model was at one time leading the rally and came fourth
overall behind three cars in a field of approximately 80 which included 11
The RT1 has been produced in response to a demand for a machine in the big class capable of competing with the British and Continental singles in European and American sporting events and in particular to take advantage of the big demand for such bikes as a result of the visits to the U.S.A. over the last two years of leading British and Continental Moto-cross men. There is a racing version of the standard RT1, known as the RT1 M, for those whose interests lie only with top-line competition.
The RT1 has been eagerly awaited in this country, particularly in view of, first, the successes of the DTI and the 175cc CT1 in numerous trials and scrambles, and secondly,
because of the victory of Roy Linley aboard this machine in the Roof of Africa. We were anxious to find out if the RT1 was a worthy partner to its smaller cousins. Accordingly, we asked Roy if we could test his machine. He willingly agreed so this test gives you not only an assessment of the performance of the RT1 but an accurate idea of the behaviour of a famous motorcycle.
The RT1 we found to be a machine fully capable of performing any one of three jobs. It is a perfectly acceptable machine for everyday riding on the roads, riding to work, going out on pleasure trips with or without a pillion passenger. Secondly, it can compete with success in club events of the more difficult sporting nature, that is to say, scrambles and foot-up trials. Thirdly, it makes an ideal enduro machine for long distance riding off the tarred roads, whether for fun or in competition.
But to begin with, a description of
the machine. The engine is a piston-port single cylinder of 351 cc (80 x 70 mm
bore and stroke) which has a two-plug cylinder head. In fact, it was not
originally designed so but had one plug and a decompressor, a popular fitment in
America and Britain for trials. The second plug fits in place of the
decompressor. The make of plug incidentally is the NGK B9E which is the
recommended plug, although for running-in the B7 is preferred. The engine has
the Autolube system, a constant loss system
The frame is of strong steel tubular
construction with twin down-tubes and twin top-tubes from the steering head back
to below the saddle. It is extremely rigid. The front end when compared with the
frame of the DTI has been strengthened. GEARS
The RT1 has inherited the DTI
clutch. This clutch system combines well with the robust gearbox and we liked
the primary kick start, whereby one can pull in the clutch lever and kick-start
in gear should the machine stall on difficult ground.
They are not adjustable as on
the DTI but are considered to be more reliable. The back shock absorbers are
also stronger and adequate for all normal road and rough work.
The electrics consist of a 6 volt lighting system with flywheel magneto and battery well protected and in position under the saddle. There is a headlight, taillight, stop-light and indicators. The petrol tank is small and holds 2.5 gallons. The saddle is comfortable and ideal for one person but hardly big enough for two although it is possible to carry two and pillion footrests are fitted. The mudguards are short and the rear mudguard leaves adequate clearance to avoid jamming of stones and mud packing; the front mudguard is also brief but rather too close to the tyre. For a semi-competition machine with a heavy tread to its tyres it would have been preferable to have a front mudguard with the leading edge close to the tyre but the trailing edge well away so that stones etc. cannot jam between mudguard and wheel. The handlebars are high and comfortable and the controls perfect. We like the anti-slip bar grips although these do not suit everybody.
The speedometer is calibrated in
kilometres and like the rev counter is mounted in rubber over the front forks in
a position where it can be seen at once. The air cleaner is an oil-impregnated
Now we come to the interesting part — the handling of the RT1 on the rough. The riding position is excellent and gives one immediate confidence. The seat is comfortable and handlebars are high and cause one to adopt the straight-backed position from which it is easy to stand up on the footrests. The footrests themselves are very safe, and although the rubbers may be torn off when travelling at speed on the rough, the rests themselves will not bend as they are designed to hinge upwards and backWards when striking an obstacle, in the modern approved manner. The position of the rests and the handlebars combined with the long well-damped movement of the suspension make it easy to ride hard over rough ground.
The frame being strong and rigid gives the bike good handling characteristics. The swinging arm is one inch longer than the DTI which in effect moves the engine mass Vi" forward. This has no detrimental effect on cornering, the front was pleasantly light when it came to navigating quickly over the twists and turns of a dirt road or across country. Allied with the longer swinging arm, the back shock absorbers, as we have said, are stronger than the DTI but it is considered that for serious scrambling, a heavier spring would give better damping action as the present action is not stiff enough and the shocks don't recover quickly enough.
to say, the spring doesn't push the plunger out fully during a series of
repetitive bumps with the result that the plunger goes further in until the
suspension is almost solid. The layout of the machine gave it no vices. The tail
end is quick-acting and can be brought round smartly
The handling in this sort of way was
always predictable and consistent.
The brakes for road work are no more
than adequate but on the rough are good. They are well designed for the job.
The acceleration is excellent, and up to about 55 mph you can hold your own with any two- or four-wheeler except those vehicles in the top performance bracket. After 55 to 60 mph the acceleration tails off until the maximum speed of 78 mph is soon reached. The engine revs freely and it is possible to exceed the maximum revs of 6 500 going up through the gears and particularly in top gear on a downhill section. The bike is comfortable and the high riding position gives excellent control under all conditions, wet or fine, town or country. Its competition breeding makes it highly manoeuvrable and in this respect it is better at town work than many road machines. Apart from the lack of weather protection it is in many respects an ideal commuter's bike, and once the handling characteristics are appreciated by the rider, it can be motored up to the limits of its performance anywhere on the tar with comfort and safety. The tank holds only 2.5 gallons bat for its purpose is neat and compact. Mileage per gallon varies between 43 and 53 according to terrain and riding methods, so a full tank will carry one between 90 and 140 miles. The petrol tap has a reserve position.
The reserve supply is sufficient for 12 miles. The mudguarding of course is strictly sporting. We felt that the front mudguard could have been longer without detracting in any way from the machine's capabilities. As it was, mud was thrown up into the fins and under the tank among the coils and wiring.
For those who would like to obtain more performance, a G.Y.T. kit (Genuine Yamaha Tuning) is available. It is a factory spare. This comprehensive kit pushes the power of the RT1
up from 30 bhp (s> 6 500 rpm to 36
bhp <s> 7 000 rpm.
To summarise, we consider that the RT1 is an excellent compromise between a scrambles machine and a road bike, that is to say, it is an ideal enduro mount. The whole machine gave the impression of a well-designed, compact, taut and business-like job which was most satisfying to ride in any conditions but particularly on those long open cross-country stretches.
Roy Linley's bike was a well-prepared and well-cared-for specimen and in spite of its hard if brief career to date, it was running extremely well. We are confident that the RT1 will find many enthusiastic owners in this country where conditions for its use in all their variety are so suitable. . •
S.A. MOTOR CYCLIST 1970