while our testers never reached sixth gear on a motocross
track. For a motocross track, fourth gear just needs to be
brought closer to third by a hair, while sixth gear is just a
paperweight and needs to be taken out.
( 4) Flywheel. To get a more tractable feel and broader
power on the 250cc machine, we stuck with the heavier
flywheel from the TX300. The stock TC250 motocross version would benefit from this.
( 5) Gas tank. We removed the large 2.65-gallon tank
from the TX300 and replaced it with the TC250’s 1.85-gal-
( 6) Electric start. If you think that a few pounds would
deter us from keeping the TX300’s electric starter, you
better think again. The TC250 weighs 211 pounds in stock
trim, while our homemade TC300 weighs 218 pounds.
( 7) Suspension. The TX300 came with WP AER 48
forks, but they were valved on the soft side for use in
offroad conditions. Since they are air forks, we could make
them usable by adding more air, but that would just be a
Band-Aid fix. The valving wasn’t progressive enough on
the TX forks. They settled into the bottom of the stroke and
delivered a harsh feel. Plus, when we stiffened the forks,
the front end didn’t balance well with the soft shock, even
though we were all the way stiff on the shock’s compression. So, we made it easy and put the TC250 shock and
forks on our TX300.
WE FOUND AN EASY YET STRANGE
SOLUTION TO OUR JETTING
PROBLEMS. THE MANUAL SAID
THAT WE SHOULD RUN A GAS-TO-
OIL RATIO OF 60:1. THAT IS NOT A
When our TC300 transformation was complete, we had
riders of all ages and skill levels ride the bike. We had our
TC250 on hand for back-to-back testing and got feedback
about what the riders liked and didn’t like. Here is a breakdown of what our testers thought about our TC300.
Every rider from beginner to Pro felt the TC300 had a
very user-friendly engine. They did not, however, collectively choose the TC300 engine over the TC250. For faster riders, the TC300 lacked the aggressive hit and light throttle
of the TC250. Conversely, the TC250 lacked the bottom-end
grunt of the TC300. Our Pros didn’t mind that the TC250
engine signed off early, because they were willing to hammer new gears all the time. They had the skill and youthfulness to choose power over usability. Still, each rider who
chose the TC250 did say that he wished the TC250 were
more like the TX300.
The Vet and Novice riders found that the TC300 was
a much better race machine than the TC250. To a man,
they turned in more consistent lap times and had more
fun in the process. The big plus of our TC300 hybrid was
its extremely linear powerband from the bottom to the top
end. There was no need to use the clutch out of corners. It
could chug second and third gear with no problem, whereas the TC250 needed some clutch work. On the TC300,
slower riders didn’t have to shift if they didn’t want to.
The top end would go flat, but it would never fall on its
face and push the weight of the bike forward. Keeping
the weight back is important, because it keeps the rear
end planted and the chassis balanced. When the weight
moves forward on a two-stroke, it frees up the rear wheel
and puts the weight on the front end, making the bike less
stable at any speed.