1975 Yamaha Torque Induction - 3-Page Vintage Motorcycle Ad

Description

1975 Yamaha Torque Induction - 3-Page Vintage Motorcycle Ad
Original, vintage magazine advertisement
Page Size: Approx. 8" x 11" (21 cm x 28 cm) each page
Condition: Good
Torque Induction is more than
a word on the outside of aYamaha.
It’s a stainless steel valve on the inside.
Here’s what it does:
At low speeds,
Torque Induction* helps prevent this.
In a conventional two-stroke
engine, something bad happens:
At low speeds, the fuel/air mixture
in the crankcase tends to blow back
through the carburetor. This is
because the intake port remains
open during most of the piston’s
downstroke.
As a result of this “blow-back”
effect, conventional two-strokes
have trouble generating power at
low speeds. And, because it changes
direction repeatedly, the fuel/air
mixture
tends to sep-
arate, leaving raw
fuel in the crankcase. This raw fuel
can foul the sparkplug and cause
the engine to stall.
Yamaha two-stroke engines have
a unique stainless steel reed valve
built into the intake manifold.
piston’s downstroke, this
valve closes to prevent fuel
from blowing back into the
carburetor. So there’s less
chance of your sparkplug
fouling.
More important, by allowing
the engine to breathe better, Torque
Induction® increases low-speed
horsepower markedly.
On the road, this increase in
low-speed horsepower means you
don’t have to shift down every time
the traffic slows down.
Off the road, more low-speed
horsepower makes it easier to lug the
engine. This helps maintain more
constant traction. More low-speed
horsepower also means you can ride
a Yamaha through mud or loose sand
with much less chance of the engine
loading up or stalling.
Conventional two-stroke en-
gines have another problem: Burned
exhaust gases have to leave the
cylinder at the same time as a fresh
charge of fuel/air mixture is enter-
ing through the transfer ports. At
very high engine speeds, this
interchange of gases becomes less
efficient. Burned gases are not com-
pletely expelled from the cylinder.
As a result, the engine doesn’t get a
full “gulp” of fresh fuel/air mixture.
Power drops off.
This incomplete exchange of
exhaust gases creates another prob-
lem: Heat. (At high speeds, the
temperature within the combustion
chamber can reach 1200° Fahren-
heit.) Without the cooling effect of
a complete charge of fuel/air mixture,
this temperature can rise to the
point where the engine seizes. Or
the piston crown actually melts.
Torque Induction® helps keep
Yamaha two-strokes breathing effi-
ciently at high speeds. As the piston
descends, a unique “sixth port”
shoots an extra charge of fuel/air
mixture directly up into the cylinder.
This gives the engine the extra fuel/
air mixture it needs at high speeds.
More important, this charge is angled
to help sweep the cylinder of exhaust
gases. The result is an engine
which generates
more power at
high speeds. And
runs cooler.
A natural
question is: If
Torque Induction
is so good,
why don’t other manufacturers use
it, too? A lot of them do. On their
B factory team motocrossers. But
» only one small European manu-
facturer has this improved induc-
tion system on its production
Z motocrossers. Meanwhile, Torque
V Induction® is standard equipment
7 on all Yamaha two-strokes. In-
cluding Yamaha street/trail bikes,
like the DT250 shown here.
If you’re waiting for other manu-
facturers to follow Yamaha’s lead,
don’t hold your breath. Because
putting Torque Induction® on your
bikes involves more than installing a
reed valve. You also have to design
new carburetors, a new type of in-
take manifold, a new type of cylin-
der, a new type of piston... well, by
now the other manufacturers are
so far behind, they probably figure
there’s no sense trying to catch up.
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