Untitled - Dubach Racing Development

ou've probably heard so much about the 2011 KTM 350SXF that your mind is on overload.
By some pundits, the KTM 350SXF has been heralded as the second coming, and the
ballyhoo was accompanied by a successful race debut in the hands of 450 World
Champion Antonio Cairoli. Historically, aftermarket hop-up companies don't put KTMs on their
"must-do" lists when it comes to making project bikes. Not so in 2011. Every company is working
on KTM 350SXF parts, pieces and paraphernalia. Why? Because of all the bikes
offered in 2011, the KTM 350SXF is selling.
Doug Dubach became a believer when, in record time, DRD
(Dubach Racing Development) ran out of 350SXF pipes, including their
entire production run of stainless steel, titanium and carbon fiber
systems. Amazingly, racers had preordered pipes before they even
laid hands on their bikes.
Like most aftermarket companies, DRD was excited to get the latest
thing and try to make it better. The high demand for exhaust systems
not only sweetened the deal, but DRD was quick to predict that the
KTM 350SXF would be embraced by Vet class riders. This is important, because Vet racers are more likely to be able to afford a cool
new bike, less likely to adhere to traditional engine displacement
class structures, and more likely to buy aftermarket parts. Early in
the game, DRD back-burnered some Japanese-built bike projects
to go full-speed ahead with testing of their KTM products.
As for MXA, we had spent more time on the KTM 350SXF than
virtually anyone outside of the KTM R&D department. We aren't
telling tales out of school by saying that we were hoping for a little
more from the 350SXF. Don't get us wrong; many of the orange
helmet crew loved to race the bike. But virtually every MXA test
rider hoped that it would fall a lot closer to the 250 side of the
spectrum on weight and a little closer to the 450 side on power.
When Doug Dubach told us he was working on a 350SXF project, we
were excited. We had b een tinkering with and tuning our KTM 350SXF for
months and had made a few discoveries-but hadn't kicked out the jams in
terms of engine development. So, we were eager to get together with one of
the sport's most famous factory test riders to compare notes. Best of all, Doug
was willing to hand over his full-race KTM 350SXF so that the MXA gang could
test it, play with it and race it.
SHOP TALK: DID THEY COVER THE BASES?
DRD teamed up with Malcolm Smith Motorsports on a joint project that both hoped
would hit a home run with buyers. Malcolm Smith's shop is one of the nation's most famous
motorcycle dealerships.
FIRST BASE: First base for DRD was to hone the 350SXF engine's power delivery. They felt
that the 350's cam profile was sufficiently aggressive and that the compression ratio was more
than high enough at 13.5:1. DRD's goal wasn't to build a time bomb, but to depend on exhaust
tuning to maintain the durability of the stocker while showcasing DRD's bread and butter-their
exhaust pipe.
Engine mods were relegated to degreeing the stock cam and porting the head. The cam timing
was outsourced, but DRD performed the head porting in-house. You won't find the service
advertised on www.dubachracing.com. but if you send in your cylinder head, they will port it,
recut the valve seats and inspect the valve train. DRD didn't notice a huge difference on the dyno
with just these mods.
Naturally, most of DRD's attention was focused on the exhaust system, and our project bike got
the titanium version. Most MXA test riders prefer to stick with stainless steel systems because
Y
FEBRUARY 2011 / MOTOCROSS ACTION 109
To make the
most of KTM's
popular midsize racer,
DR.D focused
on the engine
and had Enzo
work on the
suspension.
they offer more bang for the buck, but on their project
bike DRD wanted to mount their top-of-the-line system.
Doug felt that the KTM 350SXF had good spots and bad
spots, but wasn't as unified as it needed to be. Doug
believed that by adding more midrange and top-end
power, he could define the working zone of the 350SXF.
Most DRD full titanium systems cost $869.00, while
carbon systems cost $919.00. The Ti systems for the
2010/ 2011 YZ450F and 2011 KTM 350/450 cost $919.00.
We understand the increased complexity of the Yamaha's
loop-de-Ioop rnidpipe, but we're not sure about the KTM.
SECOND BASE: Second base was covered by Enzo
Suspension, which Doug Dubach has had a long
relationship with. On the bill were suspension revalving
(front and rear) and stiffer fork springs (0.49 from 0.46
kg/ mrn). In testing, Doug's first goal was to get the
350SXF suspension to stay up in the stroke and keep
the forks from diving when entering turns.
THIRD BASE: At third base were some carefully
chosen performance aftermarket accessories. A Turn
Tech 2.5-amp battery was aptly chosen as an affordable
way to shed almost three pounds. Hinson got the call for
clutch duty and supplied an inner hub and clutch cover.
For years, Doug Dubach's go-to tire combo was a
Dunlop 756 in the rear and a 745 in the front. With these
two tires discontinued, Doug switched to an MX51 in the
rear and MX71 in the front. Most MXA test riders could
live with this tire setup, although we opted for an MX31
front tire for deep loam and softer dirt.
HOME BASE: Bringing the project home were
Renthal Twinwall handlebars and Kevlar grips, DeCal
Works T-7 custom graphics, Motullubricants, and a DRD
hour meter.
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Engine mods were limited to a ported head and DR.D exhaust
system. The stock piston and cam were used.
Doug Dubach 's goal wasn't to
turn the KTM 350SXF into a
fire-breather, but rather to give
it one unified powerbandinstead of two distinctly
different ones that come
with stock.
FEBRUARY 2011 / MOTOCROSS ACTION 111
Renthal also supplied the sprocket combo (with an
extra tooth on the rear to help the bike rev through the
powerband quicker).
TEST RIDE: PUT IT THROUGH ITS PACES
The MXA wrecking crew put DRD's KTM 350SXF to
the test in the most difficult situations we could find in
SoCal. We drag raced up the steep hills at Glen Helen,
hammered Competitive Edge's new Supercross track,
powered through mud at Racetown and, most important,
we lined up behind the starting gate and raced the bike
in competition. In doing so, we found exactly where the
bike's strengths and weaknesses lie.
Low-end power felt a little stronger than stock on the
DRD 350, but for all intents and purposes, it was still
best to skip straight to the midrange-which was
significantly improved over the stocker. Trying to eke out
every pony we could when chasing 450s and charging
down straights required getting to the high-rpm sweet
spot as soon as possible. In stock trim, the 350SXF has
two powerbands-a slow, torquey low-end and a revving,
high-rpm top-end. That might sound good on paper, but
it is kind of schizo on the track. We preferred one powerband over two. The biggest perk of the DRD powerband
for some was more forgiving shifting points. The DRD
350 was more forgiving if you came out of the turn in a
taller gear or shifted sooner.
We were excited to do some Supercross riding on the
350SXF to see how it matched up against the traditional
450cc Supercross bike. The DRD 350SXF had its merits.
It felt light and lively around the technical course, and it
was comfortable at speed. There were places where a
450 could be a handful, but it was hard to deny that the
abundant low-end torque of the 450 was incredibly useful
for hooking up on hardpack, jumping out of a turn, and
shifting up in a whoop section. The DRD 350SXF's
titanium pipe and lightweight battery helped make the
KTM 350SXF about five pounds lighter, but to be truly
competitive in Supercross, the 350SXF needs to lose
another five pounds.
Indoors or out, the MXA test riders were comfortable
with the bend of the Renthal Twinwall handlebars, but
they were split on rigidity. Our Intermediate and Novice
testers thought the bars were too stiff, but our Pros
loved that trait.
From the factory, the KTM 350SXF is sprung like an
enduro bike. Even featherweight test riders thought that
it needed to be stiffer. As a rule of thumb, MXA
recommends dropping the stock 0.46 fork springs and 5.4
kg/mm shock spring for 0.50 and 5.7 springs. DRD didn't
change the shock spring, but they did stiffen up the
forks. The biggest difference was in the Enzo valving.
The front forks were great at handling hard G-outs, big
bumps and whoops, but when the speeds got faster and
straightaways started to get choppy, the forks beat us
up. We softened the compression considerably to try to
find a happy medium.
As for the shock, we don't think anyone under 150
pounds can run the stock 5.4 kg/mm shock spring. Since
Enzo kept the stock spring rate and tried to control
movement with valving, the shock tended to feel very
dead. We think that a stiffer shock spring would bring
some life back to the rear end.
VERDICT: INCARCERATED OR VENERATED?
For a racer, the stock KTM 350SXF's usable powerband
doesn't start to work until 9000 rpm and up. It must be
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Enzo handled the suspension chores, and tried to make the
350XF work without going to stiffer springs. It didn't work.
DR.D exhaust systems come with a magnesium end cap, a
healthy dose of midrange power and an AMA-Iegal bark.
ridden like a 250F (albeit a very powerful one). It can
never be raced successfully as a mid-sized 450. It isn't
strong enough below 9000 rpm to be short-shifted. This
is an all-or-nothing engine. MXA test riders either hated
this engine or loved it; there was no middle ground.
DRD's KTM 350SXF powerband is much better than
the stocker because the beefed-up mid-and-up powerband
expands the working zone of the engine. The power is
broader, not so single-minded, and while it's no midrange
monster, it does get started sooner. The DRD version of
the KTM 350SXF isn't the ultimate racing weapon, but it
is a nice shove in the right direction. If you plan to race
a 2011 KTM 350SXF, you should consider hopping it up
to enhance and expand its existing powerband.
Otherwise, just buy a KTM 450SXF.
For more information, go to www:dubachracing.com. 0