BEFORE THE BORE: The 2012 Kawasaki KX250F was
responsible for a war among test riders during our 2012
shootout. It was a greatly improved bike, and without a
doubt the fastest of the 250Fs. For some, that was enough
to put it in first place. For others, the Suzuki was still number one. In the end, it boiled down to a vote count, but the
Kawasaki fans continued to hold their ground. The big
news for the 2012 Kawasaki KX250F was the secondary
injector upstream of the throttle body that gave it so much
additional power. The new Kawasaki also got a rebalanced
crank, stiffer spring rates and a rework of the SFF fork with
its single spring.
THE PARTS: The Kawasaki, Suzuki and Yamaha all have
identical bore and stroke dimensions in stock configuration.
After the Cylinder Works barrel, Vertex piston and Cometic
parts, they again had the same dimensions. All got a 3.0mm
increase in bore to bring the displacement to 269.4cc. The
Kawasaki also got both cams replaced with Hot Cams Stage
2 parts and was blessed with a Factory 4.1 RCT Ti muffler
with a Megabomb head pipe. Tokyo Mods remapped the
ECU using Kawasaki’s programming software. That’s a great
option for those who don’t want to buy the stuff from
Kawasaki and haul their laptop to the track.
RESULTS: As you might expect, the Kawasaki got an
THIRD PLACE: KAWASAKI KX270F
The KX250F’s secondary
injector allows it to rev higher than most of the 250s.
When it becomes a 270, that
advantage isn’t as clear.
OVERBOARD WITH OVER-BORES
A case of diminishing returns
Kawasaki went into the test with a big horsepower advantage. With big-bore kits, sometimes that makes a difference,
sometimes it doesn’t.
increase in power. It made as much as four horsepower
more in the middle and got more at the very bottom,
below the normal MX riding zone. In this case, we saw
some diminishing returns compared to the others. As a
250, the Kawasaki starts off with more power than any of
its classmates, but as a 270, it ended up in the middle of
the pack. It lost more revs on the very top, mostly because
it had more to lose. It’s a great bike, but it didn’t get the
cc-per-cc improvement that we saw in the others.