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| Walsh
Race Craft custom built ATV with a Chromoly
Chassis & KTM 525 Engine |
The first order of business for KTM was to
pull a proven engine configuration from their
vast array of bike engines and fine tune it
for the unique demands of the racing quad. They
chose the 450cc and 525cc single overhead cam
four valve engines that have delivered reliable
performance in a number of racing bikes for
over seven model years. The 525 is virtually
same engine that Mike Walsh campaigned is his
own chassis for a few years, winning the 2002
ProAm MX National Championship. More importantly,
Mike used this engine to finish 2nd in the 2005
Pont de Vaux 12 Hour event, a grueling endurance
motocross race that over the years has brought
out the absolute performance envelope of almost
every engine configuration in existence, and
this was a motorcycle engine without the reliability
modifications that were incorporated into the
new XC quads.
The crankcases on the XC engine were reconfigured
to hold almost two liters in the enlarged sump,
eliminating the need for a reservoir tank, oil
cooler, and potentially problematic oil lines.
Both engines share the identical lower end,
which utilizes a 72mm stroke crankshaft. The
450 and 525 top ends are interchangeable, and
this adds considerably to the versatility of
the machine if the owner wants to change racing
classes or decides he needs more power for play
riding.
The 450XC’s nikasil-coated cylinder has
an 89mm bore, and the total displacement is
448cc. The 525XC engine displaces 510cc with
a 95mm piston. Both engines run an 11:1 compression
ratio. Two oil pumps handle the oil flow duties,
and tandem oil filters keep the vital fluid
fresh as long as possible. For ease of maintenance,
the filters are conveniently located next to
one another atop the transmission area of the
cases. The 5-speed transmission with reverse
is engaged by a multi-plate wet clutch that
is hydraulically actuated, and easily serviceable
through a quick-access clutch cover. The engines
are brought to life with a powerful electric
starter, and through extensive testing and tuning
the starting has been made so reliable that
the need for a kickstarter has been totally
eliminated. Fast dead engine starts were a priority
during the development of the quad, and we all
know how important of a detail this is.
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| 39mm
Keihin FCR Carburetor |
In the era of the great fuel injection race, KTM
has opted to use the proven and effective 39mm
Keihin FCR carburetor on these quads. It is hard
to argue the ease of tuneability and reliability
of the FCR, and the TPS equipped carbs are readily
available and easily serviceable. Both the choke
and hot start are located on the carburetor, and
time will tell if the hot start will be needed
often or not during mid-race restarts.
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KTM's
Unique Air Filter System for added water
protection
|
The air intake is an all-new design that is
aimed at maximum waterproofing, while still
allowing enough air flow to supply the engine.
While most ATV intake tubes attach directly
into the front of the airbox, the XC pulls its
air through the top of the airbox lid where
it is at the highest possible point to avoid
watering out. The filter is the same foam Twin
Air unit as those used on many of KTM dirt bikes,
and it is such a common part it should be stocked
by most shops. The whole process of changing
the filter can be done in less than a minute,
without the need for any tools. For race conditions
that allow a more open airbox, a removable snorkel
piece can be taken off for more airflow. If
even more air is required, there are small ducts
on the side of the air filter compartment that
can be opened up for maximum airflow.
|
| Aluminum
Exhaust Canister |
Handling the exhaust duties is a very clean
looking stainless steel header and aluminum
muffler. The 2 into 1 performance header is
a work of art, with perfect welds and a tucked-in
large diameter head pipe. The silencer design
is derived from KTM’s four-stroke bike
technology, with an aluminum canister and cast
aluminum end cap. This lightweight yet strong
design is California Green Sticker legal, and
only emits 94db. The quads are very quiet, and
with good performance and low noise it may be
hard for riders to justify installing a race
pipe. With more and more tracks and promoters
requiring sound tests and noise restrictions,
this makes for one less thing to worry about
when going through tech inspection. KTM is offering
a tuned Akrapovic full titanium system for those
seeking maximum power. This factory Hard Equipment
unit has removable muffler inserts, and still
retains a spark arrester.
The cooling system consists of a large curved
aluminum radiator with an electric cooling fan.
A thermostat helps to maintain constant engine
temperature. No oil cooler is needed, eliminating
problematic oil lines and fittings. The curved
shape and advanced ducting designs keep airflow
at a maximum.
