Hereafter CYCLE will add to our regular monthly reports from Italy, England
and Canada a report from Japan. It will be handled by a dedicated motorcyclist,
Jack Yamaguchi.
Jack is 30 years old. an active rider and well qualified, with a wide knowledge
of motorcycling throughout the world. He is employed in the Public Relations
Department of a large airline and has visited most of the cycle factories in
Italy, Germany, France and England. Motorcycling is his hobby.
Having spent three years in England, he speaks English fluently, as he does
his native language, Japanese.
We met him on our recent trip to Japan and were so impressed with his
references and knowledge of the worldwide motorcycle picture that we signed
him up immediately. His first articles appear in this issue. — Clymer.
FIRST ROAD TEST:
NEW YAMAHA
90cc TWIN
By Jack Yamaguchi
ROAD-IMPRESSION - YAMAHA 90 TWIN
This is the latest addition to the Yamaha family, and was
the biggest crowd gatherer in the motorcycle section of the 1965
Tokyo Motor Show, where it was publicly introduced.
The 90 Twin is known in Japan as “Yamaha Autolube Twin
AT-90” meaning with 90cc two cylinder engine with oil injec-
tion. It will no doubt gel a fancier name when it makes its U.S.
debut, like its brothers Omaha, Riverside and Big Bear. Per-
sonally I will settle for, say, “5th Avenue” or “Beverly Hills.”
That’s how smooth the little gem is. More on this later.
Floyd Clymer was the first “foreigner” to ride the 90 Twin
in Tokyo, even before I got hold of one. lie was so impressed
with it during the “sneak" (literally) preview, that he gave me
instructions to try it a little longer. And very happily I obliged.
Yamaha 90 Twin is the smallest displacement two-cylinder
motorcycle in volume production in Japan, or to my knowledge
anywhere in the world (if you talk about racing motorcycles,
50cc twins are quite commonplace. There is now even a rumor
that a 50cc three-cylinder engine is under development).
Now, Yamaha already had, and has, a 90cc model existing,
and selling well, in its extensive range. And a very good one at
that. It’s tlie “90 Junior IT-1” single cylinder machine, which is
a scaled-up version of YG1 known as “Rotary Jet 80” in U.S.
The single has such advanced features as rotary inlet valve and
oil injection, pushes out 8 healthy horsepower and carries the
handsome bike to a respectable maximum of 60 mph. Then why
bother duplicating the same displacement class with the new
and costly twin? There hasn’t been any official explanation here,
and everybody is wild with speculation. My personal opinion
is that Yamaha’s rival is offering a racy overhead-cam engined
model in addition to the bread-and-butter ovh 90. What more
effective counter offensive weapon can you think of than the
T-W-I-N?
Here are some vital statistics of the Twin. Bore and stroke
measure 36.5 x 43mm, and total displacement is 89cc. For the
U.S. market the engine will be enlarged to full lOOcc by increas-
ing the bore. In its present form, maximum power is quoted as
8.2 hp at 8000 rpm.
The new Twin inhales mixture through conventional ports,
unlike its single brothers which have so successfully adopted
race proven rotary disc valve system.
Engine lubrication is by popular oil injection with mechani-
cal oil pump. Yamaha is pioneer in this system of lubrication.
Incidentally, four of the five motorcycle manufacurers of Japan
now oiler oil-injection on their 2-stroke products. Yamaha calls
its system “Autolube,” Suzuki “Sei mix,” Kawasaki “Superlube”
and Bridgestone “Oil-Injection.” The remaining nonconformist
is Honda, who is specializing in 4-strokers.
The frame and suspension components are interchangeable
with the 80/90 single, but the whole machine is heavier by
some 22 lbs. than the 90 single.
The new Twin looks remarkably different from the rest of
Yamaha, with the shallower and longer gas tank with pointed
ends sharply contrasting the rounded tank of other Yamaha’s.
It does give the bike that “lean and hungry” look.
I he twin comes in two versions, one with kick-starter and
the other with starting motor. The machine I had was a kick-
start model, but “kick” is definitely an overstatement. A very
gentle “push-down” of the pedal produces the desired result,
thanks to the new Mikuni carburetors (2 of them) with starter-
pump which enrichens mixture for easier starting. If you should
stall the motor in traffic, no panic for finding the neutral. Just
disengage the clutch and push down the starting pedal in any
gear.
Once in life the engine hums and idles quite pleasantly.
Moving up from the stand-still, you will have to give a little
more gas than yon may first think necessary. Power really starts
coming on from 3500-4000 range. The Twin has very flat torque
characteristics from 4000 up to the maximum peak power rpm
of 8000.
MORE>->
Head-on viciu shoii'in^, telescopic forks.
Maximum speed of the 90 Twin is 63 mph, while the export
100 is expected to reach 65, and it covers standing start quarter
mile in a fraction over 20 seconds. Very respectable figures that
can be favorably compared with those of ,125’s.
The gear shift pattern is typically Japanese with see-saw
pedal. To shift up you push down the toe part of the pedal, but
after 4th gear comes the neutral, -then 1-2-3-4 again. You can,
of course, use your heel to shift down.
The bike is very tractable in heavy traffic of Tokyo. On the
first afternoon of this trial run, it started raining. Now nothing
is more miserable for a two-wheeler rider than Ginza (where
Yamaha has Tokyo office) in wet. The surface of narrow streets
is covered with road grit and becomes extremely slippery.. And
those Tokyo taxies are not exactly standing still. By law a light
motorcycle rider must stay on the extremely left (we drive on
the left side) edge of the road. A taxi screeches to a stop right
in front of you, and the cabbie pops open the door (power
operated from the driver’s seat). The blasted thing is in your
path, and you really haven’t got much time or distance. The
Yamaha always stops in time and in a straight line. It does have
fantastic balance. Heavy rain did not affect the brakes, either.
This is indeed one of the safest motorcycles I have ever ridden
in the rain.
The only complaint I had was the separate scats on the
machine I tried. I measure 5’7” tall, and the delicate part of my
anatomy is placed right between the front and rear scats. That’s
uncomfortable, to say the least. Of course the single “dual” seat
that comes as an option (should be standard on the export
model) should solve the problem.
All in all a very pleasant runabout. Floyd Clymer gave me
a little badge to wear. It says “I like motorcycles.” I am very
much inclined to rewrite it, “I like Yamaha Twin 90.”
Rear oieiu of I he I loin-note lar^e exhaust tubes for a small unit
Side vieic of the "90" — bored out to lOOcc for U.S. market.
The neat instrument panel. Don't let the 120 numerals on the
dial fool you — the numerals are in kilos, not in miles.
YAMAHA 100 YL-1 SPECIFICATIONS
ENGINE —Parallel Twin “100” 11 model, 2-stroke; 97cc, bore
and stroke — 38 x 43mm, compression ratio —7.1:1, maximum
torque —0.805 kgm/8,000 rpm, kick starter; WHEELBASE — 45.1 in.;
WEIGHT-217 lbs.; MAXIMUM SPEED-65-67 mph; FUEL CONSUMP-
TION on level paved road —153 mpg at 19 mph; CLUTCH —Wet,
multiple-disc.; SEPARATE LUBRICATION by Yamaha Autolube; ELEC-
TRICAL SYSTEM — Ignition coil and battery; 12-volt DC generator
system is used; flywheel magneto ignition. ____________________