An RK Z-ring chain and an Ironman stainless steel sprocket
( 49 or 50t) handle the drive-chain chores.
The Power Quiet end cap is spark-arrestor-legal, quiet and
makes for a strong power gain.
The Acerbis 3-gallon tank is very sano, slim and with smooth
lines. It gives you nearly a half-gallon more petrol and comes
with all of the crucial mounting hardware.
BDSB’s oil cover increases the capacity—always good for a
The engine is fit with BDSB’s bevy of goods, starting with
the Grunt, an exhaust manifold reducer that helps with bottom power, and the new Power Quiet end cap. Actually, the
XC-W muffler really responds to the higher-flow PQ system
that aligns with the interior core, and Dave says it makes
a 2-horsepower increase between 3000 and 10,000 rpm.
These two mods let the 500 breathe better. The power feels
freer, stronger initially and is smoother through the bars.
BDSB says at this point that the stock ECU works just
fine, though it does get just a shade leaner. Dave’s next
mod is pretty dramatic, although it’s fairly simple. He bolts
on the 450SX-F (or XC-F) 44mm throttle body with the
injectors on the bottom of the body that spray vertically.
The gains here are titanic and take the stock 53 horse-
power and 54 foot-pounds of torque to 58. 9 horsepower
and 59 foot-pounds of torque. The basic cost of the throttle
body isn’t bad; it’s under $400. It does come with a differ-
ent TPS than what the stock XC-W has, so your TPS will
have to be transferred to the new body. It’s easy to do, as
long as you can set it up. The best thing to do is get the
TPS tuning tool from BDSB, so it can be done accurately. It
needs to be accurate to work right and makes a big differ-
ence in the way the bike works in the end.
The one key to being able to make the new body work is
having the European map downloaded into your ECU. An
authorized KTM dealer has to do it, and they have to have
your bike there to do it. This is just FYI. If a shop says it
can send you a new ECU or you can send yours in to have
it done, it will cause you problems later on. A lot of this
is because matching numbers in the ECU and the bike is
how KTM is controlling the rate of stolen bikes. Dave found
that setting the TPS at . 62 and using the latest version of
the Euro map in the ECU was the very best combination.
No other maps with any other combinations of TPS set-
tings or programmers work as well as this setup.
OFF-ROAD HOT ROD