YZ250 TWO-STROKE VS.
Both hopped-up Yamahas produce 49 horsepower at peak. However, where the power peaks and how broad the powerband is make a big- ger difference than how big the peak numbers are.
fills the chamber, making the fuel easier
TWISTED DEVELOPMENT’S 2007
YAMAHA YZ250 TWO-STROKE
A ten-year-old bike, a five-year-old
bike or brand new off the showroom
floor—it doesn’t matter which Yamaha
YZ250 two-stroke you start with, they
are all inherently the same (with minor
mods). If you don’t have deep pockets
but want to compete at the highest
level, buy a YZ250 two-stroke. These
bikes, on the AMA Amateur level, can
be raced in the 250F class. Just this
year at Loretta Lynn’s, a kid won the
250 C class on a YZ250 two-stroke and
left a howling pack of 250 thumpers in
The 10-year-old, beat-up, 2007 YZ250
two-stroke we started with was rebuilt
from the ground up into a new machine.
Jamie even made it look like a 2017
YZ250 by using Applied triple clamps
to retrofit the updated YZ front fender,
bolted on the newest airbox (which
slides right on) and beautified the rest
of the bike with a Cycra Powerflow kit.
As for the engine, he didn’t go whole
hog. He wanted it to be both affordable
The price tag? $1200 and change.
Jamie blue-printed the engine to match
everything perfectly. The cases were
textured, the cylinder ported and a
Twisted Development spec piston
was used. The biggest difference was
achieved by using a second base gasket and taking the same thickness out
of the head to get it back to stock
compression so pump gas could be
used after raising the port timing.
Jamie also put in a bulletproof Hinson
clutch, which ran another $1000. What
was the pony power with the added
mods? Surprise! The hopped-up YZ250
peaked at 49 horsepower at 8500 rpm,
while the YZ250F peaked at 49 horsepower at 13,500 rpm. The kicker was
that the YZ250 two-stroke had 9 more
foot-pounds of torque than the thumper. Those kinds of torque numbers are
For the MXA wrecking crew, this
was Rocky versus Ivan Drago all over
again. A high-tech thumper against an
old-dog smoker. The MXA test riders
went out on the YZ250 two-stroke first.
Each rider had a blast. The power was
strong, playful and easy to ride. The
light engine braking of the smoker
allowed the bike to flow with ease
around the track. It got over all the