1971 Kawasaki 350 S2 Motorcycle Road Test - 5-Page Vintage Article

Description

1971 Kawasaki 350 S2 Motorcycle Road Test  - 5-Page Vintage Article
Original, vintage magazine article.
Page Size: Approx. 8" x 11" (20 cm x 28 cm) each page
Condition: Good
The Mach III is a heavy act to follow, having established
its reputation as a giant-killer. So readers will undoubtedly
be disappointed that the Kawasaki’s new three-cylinder
marvel, the 350 S2, is only one of the fastest 350s we’ve tested
rather than the fastest.
Perhaps we shouldn’t be so performance-conscious. But the
factory rates the output of this new engine at 45 bhp, which
should put it in a class with the peppiest 500s. The 350 Three
is peppy, but not 45 ponies worth. So while Kawasaki searches
for the missing horsepower, we will concern ourselves with the
virtues of the S2 as it stands. And there are plenty.
Quite obviously, the bike is intended for the performance-
minded short haul rider, rather than the long distance touring
man. While the S2 sustains highway speeds easily, it is a
gasoline gourmand rather than a moderate gourmet. To
characterize it further, it is much lighter feeling than the Mach
111 500, steers more easily, feels comfortably narrow, has
better ground clearance in corners than does the Mach III, and
will pop those same delightful (or scary) wheelies in the lower
gears.
Mechanically, the S2 has benefited from Kawasaki’s experi-
ence with the Mach III. It further sports its own unique styling
gimmick, a feisty high-riding tail molding, as well as a bright,
flashy paint job.
The S2’s engine is little more than a scaled down version of
the powerful 500-cc Hl unit. Located within the leak-free,
horizontally split, aluminum die-castings of the crankcase is a
pressed-together crankshaft with the crank throws set 120
degrees apart. Six ball bearings support the rather long crank
assembly, and rubber seals prevent leakage of air into the
separate crankcase chambers. The short connecting rods are
supported by roller bearings at the big ends of the crankshaft,
and the pistons are supported in caged needle bearings. A
slight offset of the connecting rods towards the rear (inlet)
side of the engine helps minimize piston slap by changing the
point of highest lateral combustion pressure, which occurs at
top dead center.
Oil for lubrication is supplied by a plunger-type pump
controlled by the engine’s rpm and a cable connected to the
throttle. Thus, at low engine speeds and throttle openings, less
oil is supplied, reducing exhaust smoking and spark plug
fouling. Oil from the pump is directed to the left-hand main
bearing through a plastic pipe, and is further fed to the
right-hand bearing before being mixed with the fuel/air charge
to be burned and discharged through the exhaust pipes. Oil is
also injected into each intake stub to lubricate the pistons,
wrist pins and cylinder walls.
The small 53-mm cylinder bores permit large port areas in
relation to the size of the pistons, which leads to a
theoretically more efficient engine. The three two-ring pistons
ride in cast iron cylinder sleeves, which are fitted into the
aluminum alloy cylinder jackets by a cast-in-bond process to
assure maximum heal dissipation. When the Hl first appeared,
some critics were concerned about possible overheating of the
center cylinder due to the blockage of a cooling airflow by the
front forks and wheel. Bui Kawasaki spent much time in the
wind tunnel developing a front fender design which permitted
sufficient airflow for adequate cooling.
Missing on the S2 are the cast-in “bridges” between the
cylinder fins which are employed on the Hl, presumably to
reduce mechanical noise. Perhaps the engine’s smaller size
makes these bridges unnecessary, for mechanical noise is
moderate on the S2, and certainly no more than that
emanating from the Mach 111.
The three 24-mm Mikuni carburetors supplying the fuel are
connected to the aircleaner by short neoprene hoses. When the
KAWASAKI 350 S2
“Gee, It’s Nice To
Have A Little Brother.”
clutch is withdrawn, the engine is extremely quiet at idle rpm.
and the exhaust note remains very low even in full throttle
acceleration.
The fly in the ointment is the intake roar produced by the
air cleaner when the throttles are opened wide. It’s not an
unpleasant sound, but it is one which could become tiring on
long high speed trips. A solution might be found by baffling
inside the air cleaner, or by creating a plenum chamber, which
would take up more space in an already crowded area under
the seat.
Power transmission is accomplished by straight-cut gears
from the crankshaft to the clutch. The gears themselves...
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