YZ250 TWO-STROKE VS.
Back in 2010, the MXA wreck- ing crew did an apples-to- apples comparison between
the YZ250 two-stroke and YZ250F
four-stroke. No hop-ups, just out-of-the-crate, bone-stock, head-to-head action.
At the time, the YZ250 had already
been unchanged for half a decade.
Nevertheless, the smoker won by a
landslide against the thumper. Pound
for pound, cc to cc, the two-stroke
engine was superior. Well, that’s not
100-percent accurate. We turned our
fastest lap times on the smoker, but
we also turned our worst laps times
on it. It could be faster, but it required
lots of skill to be consistent. On the
other hand, the YZ250F was like
a bank clock—tick-tock, perfect lap
times every time. The problem was
that no one believed that the YZ250
two-stroke was faster, except for the
For clarity’s sake, we need to go
back in time to understand what
has happened in the two-versus-four
rivalry. Back in 2002, the Yamaha
YZ250F made 32 horsepower, which
was 4 horsepower less than the 2010
YZ250F and 14 ponies off the 2010
YZ250 two-stroke. Now, fast-forward
to 2017, when the Yamaha YZ250F
four-stroke makes 5 horsepower more
than it did in 2010 at a hair under 41
ponies. In that 15-year span, from 2002
to 2017, the YZ250F gained a whopping 9 horsepower. As for the YZ250,
it stayed stagnant at 46 horsepower.
What does this prove? That 16
years ago, maybe even seven years
ago, a 250 four-stroke couldn’t beat a
250 two-stroke (if the displacements
were the same). Well, the times they
are changin’. While two-strokes haven’t gotten a whole lot more powerful, 250 four-strokes keep getting
more pumped up with each passing
year. By our calculations, Yamaha
has averaged a 5-horsepower increase
every seven years on the YZ250F.
And the 2017 KTM 250SXF is already
half-again as close to the YZ250 two-stroke; its 44 horsepower isn’t that far
from the YZ250 already.
Rather than wait for Yamaha to
build a 46-horsepower YZ250F, we
decided to take a quick shortcut via
Jamie Ellis’ Twisted Development race
shop. Jamie is what you would call a
top-notch, first-class, grade-A, blue-chip, five-star, under-the-radar engine
builder who has been involved in multiple AMA championships. You won’t
see a Twisted Development logo on
the championship bikes that these
big-name riders are riding. Jamie
works as a consultant. He refuses to
pay these teams for logo placement.
Heck, he doesn’t even give out free
work to these top teams and riders.
Why? Because they come to him. We
already know that he can produce
a 49-horsepower YZ250F. We know
because we’ve tested it.
When we told Jamie about our
idea of running a hopped-up 250
four-stroke against a stock YZ250 two-stroke—because that would give the
two parity in horsepower—Jamie said,
“It wouldn’t be a fair fight. The advantage will shift to the YZ250F if you do