QUICKSPIN I Slavens Racing Yamaha YZ300X
P88
Starting Point
To save on cost, the Slavens
crew found a used 2016 YZ250X
as its starting point. 2016 was
the first year for the YZ250X, the
first production Japanese two-
stroke off-road bike in decades.
Since then, the YZ250X has
seen updates, but at its core, it's
still the same bike.
Once the teardown began,
the wish list kept growing, and
the bar was raised very high: to
create a KTM killer, since the
KTM 300 two-stroke is consid-
ered by many as the benchmark
for all 300s. Slavens ended up
going all-out on their project. No
stone was left unturned, but for
the sake of space, we're going
to focus on the major changes,
like, of course, the engine.
Get To Work
To compete against a KTM
300, like the XC (cross-country)
or XC-W (enduro) models, the
YZ250X's cylinder had to be
punched out, so an aftermarket
big-bore kit from Cylinder Works
was installed. The retail price
of the kit is just north of $1000.
Not cheap, but at least it's an
easy bolt-on operation that
includes everything you need:
a nickel silicon carbide-plated
cylinder, a Vertex piston, rings,
gaskets—all that stuff. Total dis
-
placement is bumped to 295cc
from 249cc with the new 72mm
piston. The YZ's 72mm stroke
was not changed, so it now has
the same 72mm x 72mm square
bore-and-stroke configuration
as a KTM 300. There's a slight
bump in compression, too.
The Slavens boys could
have stopped there, but no. To
complement the big-bore kit,
they installed a re-mapped Vor
-
Slavens Racing selected a
2016 Yamaha YZ250X for this
project, but it looks like it just
rolled off the assembly line.
