Yamaha RT1 360
Yamaha RT1 360
Air cooled, wo-stroke, five port, single
Bore x Stroke
80 x 70 mm
- / kick
30 hp @ 6000 rpm
26.0 ft/lb @ 5500 rpm
5 Speed / chain
3.25 x 19
4.00 x 19
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 Yamaha RT1 is a larger version of the 250cc DTI. It is a cross-country
motorcycle with a single cylinder motor of 360cc capacity and is the biggest in
the current range of five Yamaha machines designed for riding on the rough. At
the same time it is a standard machine, is equipped with lights and can be used
on the road.
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
whereby oil is pumped from the oil pump to points in the inlet tracts,
lubricating the engine direct from the oil tank with oil un-mixed with petrol.
The compression ratio is a modest 6.3:1 and power developed is 30 bhp at 6 000
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
There are five gears, the first or lower three are close and the top two are
wide, the latter to give easy comfortable touring speeds on the open road and to
send the bike along smartly where conditions allow it on-the-rough. It is very
simple to change the gear ratios by removing the cover (three Philips screws and
one nut) over the gearbox final drive sprocket and changing that sprocket.
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.
The front suspension has been made stronger in that the yokes of the front forks
are heavier than on the DTI. These forks which are telescopic have long action
ideal for keeping the front wheel on the ground at speed over rough going.
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 brakes are the usual arrangement of single leading shoe front and rear.
Wheels are of steel. The front tyre is a 3.25 x 19 trials universal and the rear
is also a trial* universal of 4.00 x 18. That is to say, both tyres are of the
heavy block tread pattern. There is a cush drive in the rear hub but this wheel
is not quickly detachable as on the DTI, which we regard as something of a
drawback. We do not know why the Q.D. wheel has been dropped, but perhaps it was
in the interests of weight reduction.
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
which is good for wet conditions but for dusty conditions a paper element would
be better. In dusty conditions the foam unit requires frequent cleaning; its
position in the centre below the saddle is excellent.
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
in a power slide on gravel on tight bends, with the engine power band at
anything between 2 500 and 5 500 rpm.
The handling in this sort of way was
always predictable and consistent.
The tyres gave a good grip on all types of going except on sand, but sand is a
law unto itself and the bigger and fatter and softer the tyres within reason the
better the results one gets.
The brakes for road work are no more
than adequate but on the rough are good. They are well designed for the job.
One characteristic of the machine which we liked and which was pointed out to us
by Roy was this. Everything is so designed that should you drop the bike, the
minimum damage is done. Everything is tucked well out of the way, the footrests,
as we have said, are collapsible and the gear-change pedal is of malleable iron.
Should you bend it, it is easy to straighten again cold. This is an important
consideration for the competition rider. ON THE ROAD
We have said that the RT1 is perfectly suitable for use as an ordinary machine
on the road, and we found that it was a very pleasant mount for town and country
riding on the tar.
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.
The RT1 is easily converted for scrambles or club foot-up trials as all
electrical parts have snap connectors — headlamp, taillamp, indicators and
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
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