Ooce upon a time there was a motorcycle factory
which made ordinary motorcycles and racing motorcycles.
Their name was Yamaha. Other people made motorcycles
too, and they all were very similar. The other
factories stopped making racing motorcycles
because it cost a lot of money, and nobody,
especially the Rich Americans, seemed to take
any notice anyway, and for a long time all the
different motorcycles remained alike in so many
Yamaha kept on making racing motorcycles,
and shortly, they made the best racing motorcycle,
so everybody rode them, and everybody noticed.
A lot of people grumbled because they were so
good. There was nothing else to look at on race
days they said.
Yamaha became very wise in the ways of fast
motorcycles, so they quickly understood that
what is good for racing motorcycles is usually
of great benefit to ordinary motorcycles, so
although their ordinary motorcycles looked the
same as everyone elses, they were not. All the
others were very good, but they remained very
good. Yamaha were very good, but got better,
until they were very, very good indeed.
One day, perhaps, everybody will notice, and
then a lot of people will grumble because .
Neither Alan Aspelf'-'nor I can find a single
valid point on which to hang any criticism of
the DS7, which speaking personally is disastrous,
because constructing any test without some
good solid criticism is rather like eating a
meringue. You know it's all sugar, because that
is what it is, all sweet and lovely, but somehow,
vaguely unsubstantial. You get to the end
and feel you have missed something; you know
what I mean?
Not, mind you, that the little Yamaha was unsubstantial,
far from it, but it was so good as to make it
almost (but not quite) uninteresting. Dammit,
what can I say about a 250 that has the ability
to outperform its rider(s) in every respect?
You name it, the Yamaha did it, and always with
a reserve in hand.
As far as I can remember, this is the first
Japanese machine I have ridden that has proved
to have frictional qualities equal to European
ones. Things like tyres, suspension damping,
and brakes. Most of them fall down in one or
other aspect, even the Honda Four, till now,
top contender, but in second place now.
I have stalled for long enough; on with the
Starting. Ah yes! Saviour of my test report.
A fault! In the early stages of my short-term
ownership, before I got the hang of cold starting,*
it once or twice nearly proved to be the end
of what was to be a beautiful friendship. It
all started in Yamaha's garage at Camberwell,
London, on the first kick. To cut a long story
short, only one plug fired. I realised power
was down, but put it down to the odd choke arrangement
for cold starting, and by the time I understood
that only one combustion chamber was doing its
stuff, the dead plug was wet.
Back at the office, I. removed it, cleaned
it, heated it, put it back, but might just as
well have spent my time more wisely, for it
remained dormant, the crankcase having a reservoir
of unburned fuel' deposited in its right hand
side. Simple. I thought, undo the plug and drain
away the unwanted puddle . . . There is no crankcase
drain plug ... To transcript my opinion of that
would not only take too long, but would undoubtedly
Should you find yourself in such a predicament
with a flooded crankcase, I suggest that the
best way to reclaim the lost combustion is to
remove the fuel tank and battery, drain the
carbs, stand the bike on its seat and handlebars,
and pump the kick start for as many minutes
as it requires to drain the engine of surplus
fuel via the plug holes in the heads.
Alternatively you can risk your pistons and
do as I did. As soon as you realise that one
plug is wet and inoperative, do not stop the
engine, but switch off the fuel tap, and ride
the 'bike until it runs out of fuel completely.
This might scavenge the crankcase without adding
to it, and dry the plug. Once stopped, swap
over plugs, putting the wet one in the hot head
and vice-versa. On starting, they both should
catch; if not, repeat the rigmarole until they
In the best Yamaha manner, the machine's top
speed was not its outstanding characteristic,
and was somewhat less than at least one competitor
by a handful of speed measures. Top speed was
90 mph. Strangely enough, the speedometer proved
to be completely accurate, whereas the rev-counter
was fast at high engine speeds by 500 rpm. At
90 mph, it should have been indicating 8500
rpm, but was in fact quivering delightedly and
optimistically around the 9000 mark. Exactly
at what engine speed the error crept in is almost
impossible to decide without many hours over
the throttle and later as a desk, and for nothing
really, for at 70 mph in top gear the revs corresponded
accurately with the speedometer, showing 6700
rpm on the clock.
The manufacturers claim that maximum power
is produced at 7500 rpm. I would argue the point.
Most two-strokes' power delivery falls away
rapidly once engine speed increases beyond maximum
power output. The DS7's did not, but kept on
running until somewhere between 8000 and 8500
rpm. (The elastic guess being due to rev-counter
inaccuracy.) Even above this, power was still
coming in strong and clear, but without quite
the same urgency. In the lower gears, the rev
limit was governed by common sense and respect
for the machine rather than the limitations
of the combustion process.
Quite enough power was forthcoming from the
square twin from 2000 rpm to be usable in the
lower gears for town work, but the top two required
1000 before any accelerative response was noticeable.
From about 3000 revs, the power increased progressively
until at 5800, a surge of extra bhp got into
stride and added to the fun. Holding the engine
speed above this kept the roadspeed high enough
to deal with anything that came along, including
an R69/S BMW, who in the end admitted his inferior
performance to the Editor - - who was riding
the Yamaha at the time — by resorting
to desperate overtaking measures in town limits.
Poor show, that.
Front wheel lifting, or more accurately, skittering,
was all part of the process under hard throttling,
but due to the race-worthy roadholding of the
frame was scarcely noticed, unless the thing
was exaggerated deliberately. It was advisable,
however, to sit as far forward as possible,
and lean over the bars from a maximum effort
sprint. Gear speeds at a true engine speed of
8500 rpm were: 1st, 44 mph; 50; 62; 75; 90.
These are not the speed ceilings though. They,
besides being very difficult to pin down exactly,
are impractical due to the immense power
fall-off at the limit, especially in the higher
gears, and dilute acceleration in their accomplishment.
Road performance has been increased by Yamahas'
deliberate undergearing of the machine. Initial
acceleration is improved, and so is lapsed
time to top speed. Unlike most small-engined
'bikes, the DS7 hits the upper 80s without pause,
and only slows, even in top gear, once over
the power top, near 90 mph, hence its incredible
ability to outperform bigger engined machines
with such simplicity. Perhaps a private
owner, especially a smaller chap, might
prefer to raise gearing a little, and save on
wear, tear and fuel without sacrificing much
to maximum speed.
Induction silencing was good; no carburetter
roar being audible at any speed. The engine
itself was com-mendably silent too, completely
lacking the restless milling of so many two-strokes
on tickover. Two-stroke silencing is so much
a matter of opinion that no statement can be
more than an opinion, but certainly the Yamaha's
exhaust gases escaped with no more noise than
any other machine's, and at speed was deeper,
and so pleasanter, than the majority of two-strokes.
However good was the engine's performance,
it was outmatched by two others, the roadholding
ability of the frame and suspension, and the
brakes. They were simply marvellous, for no
matter how fast an engine might be, if the rest
of the machine cannot handle its power then
it might as well not exist. Yamaha have, in
respect of the machine's rideability, paid at
least as much attention to the pycle parts
as they have to the engine; maybe more. completely
safe. It is not exaggerating to say that faster,
safer cornering on any other roadster would
be near impossible. Braking partnered the handling
and roadholding superbly. While the rear one
was very good, as indeed most are, the front
one was beyond reproach.
As proof (to my mind) of the frame's true merit,
not even the vast Ajrierican handlebars upset
the handling. At the highest roadspeed the machine's
wheels remained perfectly in line, regardless
of the surface irregularities. Both the front
and the back end stayed exactly where they were
meant to, without a moment's hesitation or unwanted
movement. Of course, because of the touring
comfort setting of the suspension, mainly on
the rear, at the ultimate cornering speeds some
pitching set in, but without any sympathising
from the frame. Pitching, if you demand comfort,
and who does not, must be expected on roadsters,
especially small ones. Although softly sprung,
the be indulged in, but .it required a very
deliberate effort, and was nevertheless smooth
and receptive, showing no desire to grab. While
at maximum speed, it would set the tyre squealing
The electrical system behaved itself impeccably,
and appeared to contain careful thought and
design. All the switches were well placed on
the left-hand handlebar, and required little
more than thumb movement to activate them, liven
the ignition switch was above the tank for a
change, between the instruments. I do so
hate the idiotic placing of it underneath it,
as is so common nowadays. The headlamp beam
was good without being exceptional.
Seating and riding position were comfortable
except for the style universally adopted as
normal by the Japanese. Footrests were too far
forward, and the bars too high and wide, but
that is personal. Within their fashion they
were excellent. The fuel tank was too narrow
for an upright riding stance, but would be well
shaped for an English attitude.
I was not over enthusiastic about styling.
It was fussy, almost Victorian, with far too
many fiddly do-dans scattered around. Matt
black, polished alloy, and red circles cast
into the crankcase, chrome flutings on the side
panels, white broad lining on the tank; it was
too much of a good thing. The lines of the machine
were great, almost ageless in fact, and that
is difficult to achieve.
By no means the least expensive 250, the DS7
is unarguably one of the best. Its performance
abilities cannot be graphed, but only understood
on riding. Then does the company's racing interest
Mere fun riding cannot justify the DS7's considerable
ability to return an outstandingly fine
performance, with a rare consistency. Like still
waters, the middle sized Yamaha runs deep, and
requires hard, ultra-fast riding to bring out
Yamaha YDS7 Specification;
Capacity, 247 cc. Bore and stroke, 54 x 54
mm. Construction, all aluminium. Porting, piston
controlled, five port type. Crankcase, horizontally
split, also gear case. Crank shaft, built-up
construction, with centre -main bearings and
oil seals clamped between crank-case halves,
and pinned and dowelled in place. Four main
bearings, one either side of crank-pins. Main
bearings, ball race. Big ends, needle roller.
Small ends, needle roller. Connecting rods,
steel. Big ancfsmall end eyes act as outer bearing
races. Pistons, two ring type, "Teflon"
type coated to inhibit running in seizure likelihood.
Compression, measured from closure of exhaust
port, 7.1:1. Claimed power, 30 bhp at 7500 rpm.
Torque, 2.92 kg/m at 7000 rpm.
Twin Mikuni instruments. Throat size, 26 mm.
Cylindrical throttle valves, main jet fed direct
from underhung, integral float bowl. Air cleaner,
cartridge type paper element. Cold start device
operated on left-hand side carburetter
only, right-hand carburetter connected by balance
pipe only. Yamaha claim this sufficient "choke"
for right-hand side instrument.
Force feed, metered injection into induction
tract only. Pump, gear type, driven from right
hand end crankshaft, controlled by throttle
opening. 160 miles per pint recorded during
test period, including commuting, high speed
touring, and speed testing. Tank capacity, 4
pints. Quality recommended, two stroke or straight
oil only,'not multi-grade. Transparent inspection
window let into side of oil tank as level check.
Battery, 12 v 51/2 a.h. Generator, 100 w alternator
mounted on left-hand end crankshaft. Maximum
power developed at 2000 rpm engine speed. Energy
transferred through single brush pick-wfLjrom
brass face slip ring. No permanent magnets*
Rotor segments are only mag'netised from battery
current, by activating ignition switch. This
system ensures a better and more consistent
plug spark when starting over long periods of
time due to difficulty in manufacturing permanent
magnets, and high cost of same. Ignition, twin
coil and contact breaker. Lighting: Headlamp,
35/35 w. Rear and stop lamp, 6/21 w. Flashers,
27 w. Also: main beam, ignition, flasher, and
neutral gear indicator warning lights.
Primary drive, helical gear on right-hand side.
Clutch, wet multi-plate, incorporating coil
spring shock absorbers. Five speeds, up-for-up
gear change, left-side foot lever. Rear drive:
chain, including rubber vane cush drive in rear
hub. Gear ratios, 1st, 13.66:1; 1254; 10.07;
8.24; top, 6.90.
Tank material, steel. Quantity, 2 gallons,
plus 3 pint reserve. Consumption, 41 mpg over
duration of test, including commuting, fast
touring and speed tests. Slower riding improved,
matters up to 63 mpg. Four star fuel used throughout
test, but three star adequate providing
slow speed, heavy traffic density riding not
indulged in, which caused plug sooting.
All welded, mild steel tube. Twin lower loop,
single triangle braced upper. Heavy gusseting
around head, including fabricated, extended
sleeves welded to down tubes as stiffeners.
Rear end triangulated.
Front, hydraulically damped, tele-fork. Rear,
hydraulically clamped, pivoted fork, three way
adjustable for load. Bronze bushed pivoted fork
bearing, grease lubricated. Steering head bearings,
surface ball race.
Both 18 in. Tyre, front, 3.00 in. ribbed. Rear,
3.25 in. zig-zag. Both nylon corded Dunlop.
Front, 7V4 in. tls. Rear, 71/z in. sis, rod
operated by right-side foot pedal.
Dimensions and Weight:
(claimed) dry, 304 Ibs. As tested with full
tanks, tools, road dirt etc., 338 Ibs. Seat
height, 31 in. Wheel base, 52in. Ground clearance,
£343 including delivery charge
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