350 disc-valve twin, or taking a new
direction. I suspect that 500cc A7-
based twins were built and tested,
with the usual result that the bigger
the piston, the more vulnerable it
was to seizure. And the A1 Samu-
rai and A7 Avenger lines weren’t
cheap to make, with all the extra
seals, covers, and gaskets required
to implement its high-performance
disc-valve intake system.
Smaller pistons meant more cyl-
inders. Cost control meant no more
disc valves—the new engine would
have piston-port intake. Somehow
the engineers’ choice leaked to
the English magazines and was
airmailed to our little dealership:
three cylinders. Would they take the
narrow form adopted by DKW in the
1950s, the center cylinder horizon-
tal, with the outer pair upright? Or
would it be three straight across?
Kawasaki chose three-in-a-row,
but not before submitting the layout
to specialists at Osaka University for
cooling studies. One source almost
certainly consulted was Julius Mack-
erle’s “Air Cooled Motor Engines,”BELOW: Yes, there were problems—drum
brakes, skinny tires and fork tubes, shocks
that looked better than they worked. But
they were rocket ships that the miracle
of mass production could make yours for
under a grand.
still so much in demand today
that it typically goes for more than
$100. (It’s great for things such as
optimum contours and spacing for
cooling fins.) Another likely source
was the special methods used by en-
gineer Luke Hobbs to achieve equal
cooling of the 28 cylinders on Pratt
& Whitney’s giant R-4360 piston
engine. Remember—Kawasaki was
originally an aircraft manufacturer.
One clear result of the Osaka Uni-
versity cooling work is the H1’s wide
cylinder spacing, at 115mm almost
20 percent greater than in contem-
porary twins. The fins of the center
barrel and head were made longer
fore-and-aft, than those on the outer
pair—with adequate room between32 / CYCLE WORLD