To get the front end to feel the way Tyler wanted, stiffer
billet fork lugs (with a different bolt pattern) were installed
on the SDI-tuned forks. They also found that X-Trig ROCS
triple clamps, equipped with solid bar-mount inserts, gave
Tyler the stiffer feel he wanted.
With Tyler riding Kawasakis for almost 10 years, he was
a bit nervous about having to adapt to the YZ250F. Tyler
told us, “Right off the bat, I felt comfortable. The biggest
plus I have noticed has been the improvement in turning
ability over the KX250F.” As for his biggest weakness, Tyler
said, “I am pretty bad at starts, so I needed something that
a monkey could use.” So, the team took the electronics
from a YZ450F and put its Launch Control system in Tyler’s
YZ250F. A Vortex ignition was installed so that Twisted
Development’s Jamie Ellis could pull the magical strings.
Jamie tuned the borrowed Launch Control system so that
whether Tyler was half or full throttle, the bike would not
wheelie or spin—nothing but prime-time traction. Tyler’s
Launch Control map reverts back to the race ignition map
three seconds after initial launch.
Other changes to Tyler’s Yamaha YZ250F were a swap to
a YZ450F throttle body. Both the YZ250F and YZ450F throttle bodies are identical, save for the bigger YZ450F injector
nozzle. 51Fifty found that the YZ450F injector worked better with their mapping and engine package. A thinner tank,
which is a factory part, made the bike feel narrower. With
Crank Works balancing the crank, 51Fifty did away with
the engine’s counterbalancer.
On the track it was no surprise that this bike hauled
the mail. Since it was Tyler’s Supercross bike, we only
invited our Pro test riders to ride it on a Supercross track.
We were impressed with last year’s engine, but this year’s
bike had improved bottom-end response and revved out
further. The powerband had been broadened considerably,
and the broad style of power made the bike easy to ride.
It also made it easy to recover from mistakes, as it could
get back to full power without any hiccups. Our test riders
could roll through the corners in second gear and just twist
the throttle, using no clutch, to get over the triples. The
aggressiveness of the midrange power that we complained
about last year was smoothed out. This might sound like
a bad thing for a small, 250cc, four-stroke engine, but on a
Supercross track, it allowed the rear end to track the front
better. It wasn’t less powerful—just more usable. It was
less likely to break the rear tire loose. We were impressed
with the transplanted Launch Control system. It took us a
couple of tries to find the perfect position to get the traction we wanted, but once we found it, we could duplicate
the same perfect start over and over again.
Tyler is a big boy, so we knew the chassis would feel
stiff; however, the faster our test riders rode, the better the
bike handled. The front end pushed if the bike wasn’t powered hard enough into the corner, but speed cures many
ills. Make no doubt about it, the feedback from the rigid
front forks was intense. We could feel every bump, rut and
pebble. At first this made the forks feel horrible, but even
though the front end was incredibly stiff, it was capable of
absorbing the big jumps or big mistakes—you give to get.
Overall, the 51Fifty Yamaha YZ250F was what we
thought it was going to be—after all, we have been with
them every step of the way during their Yamaha journey.
Tyler’s bike was, in the plainest terms, stiff and fast. This
bike stands toe to toe with the factory-backed 250 four-strokes. As with all privateer teams, the difference between
a factory team and the 51Fifty team is money and resources. They are running a part-time staff, living on a budget,
outsourcing parts and relying on the largesse of team
owner Carlos Viera. Now, imagine if these exact same guys
got the backing of a factory team; they could reach the top
of the food chain. ❏
Tyler likes the front end to feel super rigid. Stiff KYB billet
fork lugs were added to suit his needs.
This engine may not be factory, but it sure felt like it on the
track. Twisted Development knows their stuff.
A YZ450F launch control switch was mounted on Tyler’s bike
to help him with starts. It helped him get better starts.
SDI Suspension takes care of the entire 51Fifty team. They
are as close to factory forks as you can get.