❏ Back in 2003, Suzuki helped revolutionize the world of ATV racing by
introducing the four-stroke Quadsport
400. At the time, Suzuki and Kawasaki
had joined together to produce the
same machines under different colors
and company names. The Kawasaki
KFX 400 is exactly identical to the
Suzuki LT-Z Quadsport 400 in almost
every way. These ATVs are sporty and
fast with an extremely durable motor.
However, with the development of
450cc ATVs, the 400cc engine can’t
keep up. This ATV was once at the top
of the podium as a race machine, but
it is now considered a trail quad. For
this budget build, we wanted to bring
this ATV back to its roots as a racer yet
make it a blast out on the trails.
Left over from the Kawasaki and
Suzuki alliance days, we found a KFX
400 that was still in amazing shape.
We wanted to add power to the
engine, along with some safety and
handling items to make our older ATV
feel more like a newer 450. If you think
that adding a bunch of bolt-on mods
will make your 400 act like a sport 450,
you might want to think again. Unless
you plan to spend far more than the
used ATV is worth, it won’t be on the
same level as a 450, but it will turn into
a much better machine. We wanted to
keep the modifications and bolt-ons as
simple as possible, so we headed to
Rocky Mountain ATV/MC to get all the
needed parts for this project.
Increasing power from the durable 400cc engine was the first step.
Whether you’re riding trails or you want
to take this ATV to the track, the added
power from the Cylinder Works big-bore
kit and the Hot Cams gave our budget
build new life and the means to keep up
with sporty 450cc ATVs.
Power modifications were an important part of this build. Cylinder Works
hooked us up with a 440 big-bore kit,
which includes a Vertex piston and
Cometic gaskets. The addition of the
Hot Cams turned this 400 into a rocket.
Nerf bars are a must for safety, and
Tusk has simple, inexpensive, bolt-on nerf bars for a lot of popular sport
quads, so we decided to put a pair on
along with their polished front bumper.