WR Cylinder WKS_pg100-104:Layout 1 11/28/11 2:31 PM Page 2

WR Cylinder WKS_pg100-104:Layout 1
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We Ride
CYLINDER WORKS’S
KAWASAKI KX269F
I
t’s easy to think that Cylinder Works is pandering to cheaters with their
line of big-bore engine kits. There is no doubt that cheaters are drawn to
what Cylinder Works has to offer, but, in truth, most big-bore engine kits
go to riders who are not bound by displacement rules (Vets, play riders and
offroad racers). However, there could be just a hint of pandering to cheaters
in that you can’t tell a 269cc Cylinder Works cylinder from a stock-bore OEM
cylinder. (They even put the same casting numbers on their jumbo cylinders.)
The Cylinder Works KX269F kit is unique in that it is designed to fit on the
2012 dual fuel-injector Kawasaki KX250F. With an 80mm bore (3mm larger
than the stock KX250F’s 77mm bore) and the stock stroke, the Cylinder
Works KX269F bore-bore kit actually produces 269.42cc. The companion parts
to the Cylinder Works casting are a Vertex piston and Cometic gasket kit.
This is one sweet deal. For $599.95, Cylinder Works supplies a purpose-built
cast cylinder (that has been nickel-silicon-carbide-plated), 80mm forged Vertex
piston and all the gaskets necessary to slip this sleeper cylinder onto your
KX250F. No machining. No drilling. No exotic regimens. Just replace and go. At
least, we wish that were the case. Unfortunately, it isn’t that simple. The fly in
the ointment is Kawasaki’s creative dual fuel injection. When we tried this
269cc kit on our 2011 fuel-injected Kawasaki KX250F, it ran without a hiccup
(and we even tested the 269cc kit on the Keihin carb-equipped
Yamaha YZ250F without problems). We had no hassles with
single injectors or FCR carbs, but Kawasaki’s new dual
fuel ignition didn’t like going big.
MAKING SENSE OF THIS
To make sense of this, you need to
know how dual fuel injection works.
For 2012, Kawasaki has equipped
their KX250F with two separate
injectors. The 2012 KX250F’s second injector is located inside the
air boot. Both Kawasaki injectors
have the same output capacity.
Only the first injector, in the throttle body, is running up until 7000
rpm. Then, at 7000 rpm, the
upstream injector in the air boot
kicks in and gradually increases
fuel delivery, while the first injector gradually tapers off. When
the bike is running wide open,
only the upstream injector is
working. Dual injectors make
CPU programming more critical. The two injectors must
function together seamlessly
to optimize fuel delivery.
When several race teams tried
using a secondary injector
simultaneously with a downstream injector, it didn’t work.
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KX269F
The secondary injector needs to come into the action
when the engine rpm is high enough to take advantage of
it. The extra time it takes for the upstream injector’s fuel
to reach the combustion chamber must be taken into consideration.
When we tried to run our Cylinder Works KX269F with
the stock 2012 Kawasaki mapping, it popped, banged
and sputtered. We were confused. This kit had performed
flawlessly on the single-injector 2011 KX250F, but
wouldn’t work on the 2012 dual-injector model.
It soon became obvious that the bigger piston
translated into a bigger combustion chamber. The larger
combustion chamber meant more air volume, which
meant that we would need more fuel. Luckily, with
modern ECUs, it is possible to increase the amount of
fuel that the injectors deliver. So, with the help of Tom
Morgan, we developed a new fuel map that increased
the amount of fuel to keep the engine from running lean.
On a side note, carbureted engines do not need to
artificially produce more fuel because carburetors
function via a vacuum in the intake tract. If you draw
more air into the engine, the carb will pull more fuel out
of the float bowl to compensate.
In short, to run the Cylinder Works KX269F big-bore kit
on your 2012 Kawasaki, you must reprogram the ECU
(just the fuel side, not the ignition map). Unfortunately,
Cylinder Works will not provide black boxes or reprogram
existing boxes, but they will supply the map. It is up
to the buyer to get his local shop or friend with a
programming tool to put in the new fuel map.
SHOP TALK: PIECE BY PIECE
Although you can just bolt the cylinder and piston
onto your stock KX250F, we decided to go a couple of
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For $600 Cylinder Works turned our
KX250F engine into a KX269F. It
would have been a simple project
except for the mapping required on
the dual fuel injectors. Without
reprogramming, you couldn’t get the
KX269F to run.
When you go big you gain horsepower, but lose some of the
engine’s flexibility. We gained midrange, but lost top.
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This is what a boatload of
torque can do to a berm.
We geared the KX269F
lower for slow riders and
taller for fast riders.
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KX269F
We loved the Moto-Master front rotor. It looks like a buzz
saw, but grips like glue to help bring the KX269F to a stop.
steps further by changing out the cams. We elected to
run Hot Cams Stage II intake ($179.95) and exhaust
($199.95) cams. There is no secret here. When you bigbore a 250cc four-stroke, you get a massive amount of
low-to-mid power, but tend to lose top-end because the
big piston just doesn’t push through the air as easily as
the smaller one. By changing cams to Hot Cams’ new
2012 cam set, we hoped to mitigate the loss with
increased torque at around 9400 rpm.
We also ran an FMF Ti Factory 4.1 exhaust with a
MegaBomb resonance chamber. It’s generally assumed
that if you are racing a 2012 KX250F, you already have
an aftermarket exhaust system. We didn’t, so this was a
logical mod for the MXA wrecking crew to make
whether we big-bored the engine or not.
TEST RIDE: PUNCHING BIG HOLES IN THE AIR
Step one: Once we were finished with the mechanical
parts of the Cylinder Works KX269F, the first step was to
take it out for a photo shoot. This is a quick and easy
way to break in the engine, get the photos shot (while
the bike is still in one piece) and establish a criteria for
what we need to change on the setup.
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Step two: Race it. As a rule, we have two or three
different test riders race a test bike on its maiden
voyage. This gives us sufficient feedback from a wide
range of riders. It also gives us a base to work from.
Step three: Consult the dyno. We ran the stock 2012
KX250F a week earlier to be sure that we had a good
baseline. The stocker is impressive, so impressive that we
never really thought of it as a candidate for a big bore—
largely because it pumps out 39.55 horsepower, has an
awesome power curve and has top-end over-rev that is
mated to constantly increasing power. The 2012 Kawasaki
KX250F has the best 250cc four-stroke engine we have
ever tested. The bar was set very high for the KX269.
The Cylinder Works KX269F pumped out 40.80 horsepower at 10,800 rpm. That was a healthy 1.3 horsepower
at peak in favor of the KX269F. Additionally, the power
below peak was a slam dunk for the big bore. The
Cylinder Works engine made two horsepower more at
8000 rpm, 2-1/2 more at 9000 rpm, two horses at 10,000
rpm and 2-1/4 at 11,000 rpm. These are great numbers
and exactly what you would expect out of a big-bore
engine.
Where the dyno chart wasn’t as rosy was at high rpm.
From 10,800 rpm on, the big-bore KX269F started to fall
off, and by 12,000 rpm, the stocker caught and passed it.
At the point where the stock KX250F engine peaked, it
was making 1-2/3 more horses than the Cylinder Works
KX269F. This was also no surprise. Big bores don’t rev as
well as stockers—and there is little you can do about it.
Step four: Analyze it. On the track, we found ourselves being limited to 10,800 rpm. Yes, the KX269 would
rev past 10,800, but that was a false top that didn’t
reward the test riders with thrust. Going to the rev
limiter actually slowed the bike down when compared to
shifting at or slightly below peak.
Although test riders like to complain, they were more
than willing to take advantage of the extra horsepower
in the midrange and use it to the fullest. From idle
through peak, the KX269F made more power than the
stocker. The stocker’s only advantage was that it revved
free. It revved high, and it made power all the way to
12,800 rpm.
We had some gearing issues that ran afoul of the
ignition mapping—which, although it allowed the KX269F
to run, didn’t seem to be perfect. When short-shifted, the
KX269F wanted to bog and required a deft touch of the
clutch to keep it percolating. Some test riders chose to
downshift for tight sections rather than risk having the
engine bog, while others opted to change the rear
sprocket to suit their riding styles or tracks. We geared
taller for faster riders and tracks, and lower for tighter
tracks and slower riders. This way the fast riders could
stay in a gear longer, while the slower riders could get to
a taller gear sooner. Either strategy worked very well.
We would expect better fuel maps for this engine once
it gets into the hands of more tuners.
VERDICT: WHAT DO WE REALLY THINK?
In a world dominated by racers, the Cylinder Works
KX269F kit would only appeal to cheaters. That,
however, is not the modern reality of offroad riding.
Thanks to the popularity of professional practice riding
and the growing number of Vet racers and play riders,
the market for a big-bore kit is not limited to the larcenist.
For a reasonable price, a KX250F owner can gain
horsepower, midrange and torque without the downsides
of high-compression pistons, head porting or exotic DLCcoated buckets. Going big may seem rudimentary in the
world of high-tech tuning, but it gets the job done.
For more information, go to www.cylinder-works.com
or call (515) 251-4070. ❏