Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125819
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ElI8n if your socks 189, the Norton is more fun
by the Claw and Ov<:r-rev
ley
are both big tWins. Torquey,
throbbing, large, studly-looking
macbines. Both Yamaha and Norton
have sought to make their big bore
twins overcome the traditional bane of
big twins: vibration. Both have had
som<: success. Both have produced a
machine that is significantly different
than the rash of big bore multis
produced by almost everyone else, and
both have provided good alternatives to
those multis, alternatives that we felt
made . the twin a more desirable
motorcycle than the alternate multi for
most uses.
Because they are twins they can be
lighter and narrower, which in tum
means that they can corner, stop, and
handle more easily. Because they are
twins, they don't put out the peak
horsepower of the mul tis, but their
ligh tnc:ss and low end torq ue gives them
back what they Jack in power. What
they give away in high RPM power they
make up for in off-line drive and
top-gear passing.
TECHNOLOGY
DEVELOPMENT
I
VERSUS
Two completely different schools of
design th ough t go in to the N orton and
the Yamaha engines. Th'e Japanese are.
famous for quickly putting together
innovative ideas that work. The Yamaha
is an example. While the Yamaha might
have had as much as three years
development time, that is a drop in the
bucket compared to the time that has
'gone into the Norton. At the same time,
the Yamaha overshadows the Norton in
technically risque ideas. An overhead
camshaft, vacuum carburetors,
omni-phase halancer, and five speed gear
box arc words the Norton just wouldn't
understand, or, for the most part, need
to.
The Norton's hints of technological
excellence fall more into the range of
afterthought than do the Yamaha's.
lsolastic suspension, Norton's rubber
engine mounting system, sounds
impressive enough, but it's really an
exterior .afterthouj!ht to make a lumpy
to
ride then the Yamaha.
engine smooth. All this would sound
bad for the Norton except for the fact
that it is smoother than the Yamaha.
Not only does it produce less vibration,
but that which it does produce is not
nearly as annoying as the Yamaha's.
For two' bikes that compare
favorably in performance and even in
the manner in which they perform, they
are technically very different. The
Norton carries its camshafts in the cases
and uses pushrods to actuate overhead
valves via rocker arms. The Yamaha
carries a single camshaft up top, but also
lacks direct valve operation. Hence,
operating RPM might be a little higher
for the Yamah because of 'slightly more
accurate opening and closing.
However, the operating RPM
difference is really represented in the
bore/stroke ratios. The 850 Commando
is really a 750 bored out four
millimeters to get 828cc. The resulting
bore/stroke ratio is 77/89mm. The
Yamaha tags in with a ratio of 80 to
74mm. They have very different
piston