On the dyno the 2015 RM-Z450 made the same power as the
2013 and 2014 models. It ranks fourth in peak horsepower.
Suzuki offers interchangeable map plug-ins. Most MXA test
riders choose the white coupler.
Every MXA test rider likes the Suzuki RM-Z450 engine.
There are faster engines on the track, but not necessarily
engines that allow you to go as fast as on the mellower
Of course, going fast on an engine that gives up as
much as 4 horsepower to its hyperkinetic competition
means that you need a talented left foot to keep
working the sweet spot, which is definitely not in the
upper reaches of the realm.
You have to shift, and shift quickly in the lower gear
ratios, to make the most of what the RM-Z450 delivers.
Top-end power and over-rev are not the RM-Z450’s strong
points, so you have to get into taller gears to get the
engine to pull longer. But, if you shift too soon or too
late, it won’t pull harder.
Q: WHICH PLUG-IN MAP IS BEST?
A: Suzuki offers three different map couplers that
can be plugged in to change the powerband. Here is
how they work.
Black coupler: Black is the stock coupler, and it
works across a wide range. Strangely, the black coupler
was the best map for the dyno, but it was not the first
choice of test riders for racing.
Gray coupler: On hard, dry and slippery tracks,
this plug-in is worth its weight in gold. It fine-tunes the
power delivery so the rider can use the power to its
fullest by not allowing the engine to produce power to
its fullest. This is definitely not the map you would want
for loam, sand or well-prepped dirt.
White coupler: Strangely, the white coupler
produces the best on-track power, but the dyno doesn’t
see it. That’s not all that odd, as the dyno never saw any
advantage to long-rod Yamaha YZ250 two-stroke engines,
but every test rider did. For the MXA wrecking crew,
the white coupler is the best choice because it adds
personality to the RM-Z450’s powerband.
Q: HOW DOES THE 2015 RM-Z450 HANDLE?
A: It handles the same as all Suzukis have handled
since 1982. The 2015 RM-Z450 is unsettled at speed. It
gets twitchy over rough ground and can be a bit of a
bucking bronco in potholes; however, we don’t think that
fear of high-speed head-shake is a good enough reason
to give up the RM-Z450’s prowess at low speeds. The
RM-Z450 trades any semblance of civility at high speed
for a chassis that carves like Douglas Fairbanks’ sword
work in the turns. It can turn inside any bike, save for
another Suzuki, with ease. There is no hesitation in tight
turns; this bike wants to turn.
There are two caveats to Suzuki handling:
(1) Motocross handling is a compromise. A bike has to
be able to turn tight turns at low speed but still dance
across high-speed straights while bouncing off the tops
of the rubble. As a rule of thumb, extremely stable bikes
don’t turn, and bikes that turn aren’t as stable at speed.
For once, common sense is 100 percent accurate.
( 2) Fork height is critical on the RM-Z450 because of
its unique frame geometry. If you lower the fork legs
too much into the clamps, the RM-Z450 will become
more stable, but it will turn like a wheelbarrow (or a
Kawasaki). If you slide the fork legs too high up in the
triple clamps, the bike will oversteer. For every track,
there is a perfect balance point. It’s up to you to find it
by fiddling with race sag and fork height.
Q: HOW GOOD ARE THE SHOWA SFF AIR
A: First and foremost, they are light years better
than the RM-Z450 forks that Suzuki foisted on the buying
public in 2014. That said, the 2015 Showa SFF Air TAC
forks are a blessing—and a curse.
The Triple Air Chamber forks have three distinct air
pockets. And, if all you had to do was put air in them
and go ride, life would be sweet; but, it’s not that simple.
Every time you change the pressure in one chamber,
it affects the pressure in the other two chambers.