During the birth of the modern day motorcycle,
no one had any hard and fast ideas about its perfect shape and form. When
Honda created the inline four cylinder Superbike in 1968, the rest of the
leading protagonists shot off in different directions simply to avoid
copying, all to return at some point, some within a few short years and
others around ten years later. In between times all began creating various
guises of machinery, lets just say it was hard to become bored with the
variety on offer.
Kawasaki S1 250Kawasaki’s bent, following the crazy 500 triple of 1969, and
with nothing but aged twin-cylinder two-strokes to call a small capacity
line up, was to create a whole range of similar looking machines, all using
the same basic layout of an air-cooled, inline, piston-ported, triple motor.
The engine being the dominant feature of all of these new three-cylinder
machines, sticking out level with the riders feet, and with a brace of
exhaust pipes winding their way from the front of the cylinders down and
under the cases before flowering into a lop sided array of chrome work by
the rear wheel. One feature this new line up had that stuck however was the
seat fairing, a common sight nowadays, but really advanced and radical
thinking back in 1972, this plastic extension to the rear of the seat also
allowed a small storage area to be built in as the 70’s biker found himself
carrying bottles of oil and the like. This short period of design excellence
aside , nothing else really stood out as advanced thinking, the chassis
being of basic construction and, while the rest of the two wheel world was
waking up to hydraulic disc brakes, the small kWaks made do with drum
stoppers all round, albeit with a reasonably powerful, 180mm
twin-leading-shoe affair on the front. In 1973 the S1’s big bore brother the
350cc S2 did get the disc treatment but for some reason the S1 didn’t. This
could have done little to help sales of the type in the UK as by this time
the learner brigade had been introduced to this technology by other
manufacturers, in fact the Kawasaki would have to wait a further three years
for this to be implemented.
Kawasaki S1 250 TripleThe engine layout, with its smooth power delivery so
typical of a 120 degree crankshaft, worked well with the larger capacity
machinery in the range, especially the stunning H2 750, but when utilised in
a smaller package the 250 and 350 versions were left wanting, still, it was
enough to make the Kawasaki two stroke range stand out from the twin
cylinder bikes of Yamaha and Suzuki, certainly in looks, even if the
performance was left somewhat lacking. The Kawasaki triple engine is
standard fare for any one who has ever stripped a horizontally cast power
plant. The gears sit in the bottom case along with the crank with just the
added cylinder sticking out on the timing side. Twin lipped, rubber seals
provide the seals between each crank, this adds to the friction losses
greatly, Yamaha had a lot of things right with their frictionless, labyrinth
seal design but, of course this couldn’t have been used, even if patents etc
allowed it, due to the uneven firing order that would see one side of the
crank with a differential in pressure to the other two. Instead Kawasaki
chose to run straight cut primary gears, these are far noisier than the
opposition helical designs but at least they transferred the power from the
crank to the gearbox with minimal losses. The outright power was there, the
S1 produced around the same as the equivalent Suzuki and Yamaha 250’s of the
period, but the internal friction losses were higher and the peak torque far
lower. The result is a peaky engine that never really gets a move on until
the revs are way up around the dusty end of the tacho and to keep it on the
boil does take some fancy clutch and footwork, not really the stuff of the
learner market place.
Kawasaki S1 250 triple engineGetting a leg over the S1 reveals it to be a
small machine, the engine dominates the image but, once sat in the low
saddle it is barely noticeable. A short prod to the kick-start lever has the
triple burbling away, unevenly at first as the pistons and rings heat up and
swell to fit snugly in the bores but, within a few short blips of the
throttle, all is well and the engine happy to go. Select first and start to
release the clutch to provide forward go and it soon becomes clear that at
low speed and in traffic the clutch lever is going to become a close friend.
It feels like an age until it can be fully released or risk stalling the
engine. Anywhere below 6k on the tacho is of little use in the real world,
its ok if you are in second or higher as a quick stomp down on the lever has
the piston-port engine buzzing and raring to go but, if you are already as
low as you can go in the five speed box, it is time to call on your new
found friend, the clutch for some help getting away.
S1 250 TripleAlthough the sound the three pipes makes is a speedy one, on
the road the S1 doesn’t feel fast and that is simply because it isn’t, top
speeds near the ton have been claimed but in reality high 80’s and low 90’s
are the norm for a well cared for S1 or KH250, and way less than those
figures if ridden two up. A standing start from the lights will have the
kWak lagging behind too, with a standing quarter around the 17 second mark
the triple is likely to have a good go at the Honda twins of the period but
anyone with any sense would shy away from taking on the RD and GT at their
own game. Even then when well on the move it is still a good idea to give
those two a wide berth as they excel in all areas except looks, park up
alongside outside the chippie by all means but, when the engines fire up,
find a good excuse and head the opposite direction, or even better still
stay behind and talk to the girls at the bus stop about how nice the bike
looks.
Kawasaki S1 250 Road TestSharing the same chassis, engine bottom end and
dimensions as its larger capacity brother, the 350cc S2, the baby of the
three-cylinder family is too heavy for the few horses it does create. There
is no power to be had, or used in anger, below 6000rpm and even then things
are a little slow developing, the engine starting to show some interest
around the peak of the torque before running out of puff less than a grand
later. Keeping the engine on song with three of every thing to contend with
was never an easy task, the slightest upset in multi carb and contact
breaker set up would create an uneven engine and considerably sap the power,
the difference between a finely tuned and not so fettled version is immense
when sampled alongside each other. Get it all right, stomping gears in as
required and the cat takes off as if mildly scalded, however allow just one
of the many permutations to wander out of sync and the disinterested pussy
is left with a lot less go. The same can be said of the front brake too, get
it set up as the book says and it is capable of a convincing stooping
experience over short periods, let it wear or get out of adjustment and be
ready for clean set of pants especially when trying to stop in a hurry from
the bikes top speed.
The chassis is more than capable of holding the engine in check during
normal upright use and, were it not for the pipes bulking up the midriff,
the S1 would have a decent amount of ground clearance, as it is however, the
kWak does drag itself around corners when ridden with a sporting enthusiasm.
This is no bad thing as it acts as a limiter to the way the bike is ridden,
but it is a shame as the short wheelbase should have yielded a snappy and
exciting ride however, at speed, and with fast changes of direction the bike
appears to have a change of mind mid corner, the front end follows the
riders inputs with accuracy but something is lacking mid chassis, it feels
as if a small hinge is built in and the rear end isn’t so firmly attached.
Kawasaki S1 250 ReviewAs a bike of its generation the Kawasaki certainly had
the looks to beat the rest, however the big K did chicken out when compared
to the other motorcycles they had produced both at the time, before and
since. Gone was the adventurous and daring ethos seen in the big bikes of
the range; instead we got a mild mannered and not so hot 250cc machine that
got slower as tie passed, no doubt the US market played no small part in
this as well as the impending UK learner laws and Kawasaki simply milked the
deign for all it was worth over the next 8 years until the type finally
disappeared from the showrooms in 1980.
Kawasaki S1 and KH250 Timeline
1972 – S1 chassis number S1F-00001
The first of the quarter-litre triples and, with a claimed 30bhp, by far the
most powerful. Kawasaki were keen to establish a reputation in the smaller
capacity classes and thought the mini 500 would do just that. Front mudguard
colour is matched to the bodywork for this early model.
1973 – S1A chassis number S1F-04691
A chrome front mudguard was the only significant external change, the S1A
was offered in three different colour ways, however a drop in power to 28bhp
was also implemented.
1974 – S1B chassis number S1F-12001
Now minus the friction steering damper but sporting a new design seat and
the locking filler cap from the Z1. This model, with the new switchgear
allowing the choke to be mounted on the left handle bar, was only offered in
one shade, Candy Green.
1975 – S1C chassis number S1F-16300
The chrome side panel badges were replaced by stickers and the wheels now
sported wider tyres with 3.25 and 3.50 front and rear respectively. Halibut
blue being the only colour for this year.
1976 – KH250 A5 chassis number S1F-24400
Revised clutch actuating mechanism marked the major change for this short
lived interim model, noise and emission regs started the decline of the type
too as restrictive exhausts introduced across the triples range dampened the
engines enthusiasm.
1976 – KH250 B1 B2 chassis number KH250B-000001
The steel fork lowers were replaced for lighter, alloy items that now
sported a 277mm single disc brake grabbed by a single piston-floating
caliper.
1977 – KH250 B2 chassis number KH250B-008601
Although externally identical to the B1 the total power was knocked down a
further 2bhp to just 26, making competing with the ever-faster machinery
from Yamaha and Suzuki even more difficult for the heavy triple.
1978 – KH250 B3 chassis number KH250B-018501
Minor updates, the shape of the seat, and a new design, triangular shaped,
front brake master cylinder set this version apart from the earlier models.
1979 KH250 B4 chassis number KH250B-025001
The side panels were no longer colour matched to the rest of the bike, being
finished in plain black, three scheme were offered White, Lime green and
plain red although the latter is extremely rare.
1980 KH250 B5 chassis number KH250B-028701
The end of the line for the triple two stroke. Now offered only in Kawasaki
racing green as a mark of their series of wins in the 250 and 350 world
championships, the road machine bearing no resemblance to the race bike
however. The KH was dropped from the side panel logos and now printed in
large white lettering on the seat cover
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