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We have known for some time that Yamaha was going to come into the 1978 model year with a brutish, four-
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cylinder in-line shaft-drive superbike; we
just didn't know until recently how big and how brutal the new model was
going to be. When the successful XS750D three-cylinder shaftie appeared last
year, a lot of people naturally assumed that a fourth 250cc cylinder would
be appended to the machine to represent the company in the marketplace
against the KZ1000, the Honda Gold Wing, and the impending GS1000 Suzuki. As
a matter of fact, a prototype "XS1000" four-cylinder, triple-disc-brake
shaftie was shown to members of the motorcycling press, and the Yamaha
dealers, in January of this year, to resounding oohs and aahs.
But that particular motorcycle never appeared - primarily because it never
existed. Yamaha had led us all down the garden path, because the XS1000,
even as it was shown during this past winter, was a ruse, never intended for
production. What does exist, and what will be coming into the country in
appreciable numbers starting next month, is that prototype, almost to a T,
with the exception that the powerplant in it is a full 1100cc, pumping out
95 horsepower, thus
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making it the most powerful, and the fastest, production motorcycle you can buy. The XS1100 is capable of speeds in excess of 135 mph and 11- second quarter-mile times.
The XS Eleven is one very modern motorcycle design, and its engine is at the
heart of it. The four-cylinder, four-stroke DOHC engine features four huge
Mikuni BS34 constant velocity carburetors, 9.2:1 compression ratio,
transistor-controlled ignition with a vacuum advance system, several types
of emission controls, rubber mounting of engine to chassis, and an internal
electrical switch that shuts down the ignition system when the bike is
leaned over at any angle greater than 60 degrees from the vertical. The
cylinder head is completely different from that used on the three, with
splayed ports, a different chamber shape and a modified valve layout. While
the two powerplants share stroke dimensions at 68.6mm, the very narrow four
uses a 71.5mm bore dimension (1101 cc total displacement) and shares only a
handful of parts, such as connecting rods, with the three. Externally, the
1100cc four bears only a slight re- semblance to the 750cc three, with new
cam boxes and a totally bright finish, as opposed to the flat black used on
the barrels and cases of the 750. And the best part is that the rest of the
machine is up to the same level of engineering sophistication as the
dynamo-smooth 95-horsepower
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engine, an engine capable of putting this bike into the 11-second twilight zone, right off the showroom floor, or around-the-world touring.
The chassis and suspension for the 1100cc superbike are derived from the
latest version of Yamaha's 750 shaftie, the E model, which was given more
power and lower gearing late in 1977, to improve its performance against
other bikes in its class. Of course there is no other bike in the XS
Eleven's class at the moment, but the 750E was a good starting place for the
Yamaha engineers to build a frame and suspension. The XS Eleven, built to be
both a superbike and a super touring bike, is quite long, 89 inches overall,
with a 60.8-inch wheelbase, exactly three inches longer than that of the
XS750E. The length distributes the machine's 610 pounds over a longer
distance, and the increased distance between the wheel centerlines at the
pavement helps the super-compliant suspension take the harshness out of
bumps and ruts in the road surface. The front forks are rated at 6.9 inches
of total travel, and the rear driveshaft/swing arm is rated at 3.15 inches
of travel, both figures the same as the lighter XS750E. Another feature
carried over from the 750 to the 1100 is the convenience of easily
adjustable front fork spring tension. The top of each fork tube is fitted
with a rubber cap, and once the cap is popped off, the fork spring tension
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