INSIDE KTM's BAJA BIKE

 
(9/9/2012)
 
 
 
 The powerhouse known as KTM, a smallish Austrian concern just a few short years ago, has slowly pounded nearly every facet of the dirt bike world into paste. Their latest goal in the off-road racing world is conquering Baja, a stark world that has been the stomping ground for green and red machines for over two decades. Racing Baja is a huge endeavor, and one that requires years of building provisions for crucial pit support; racers who have knowledge, wit and grit to perform at incredible speeds; and, of course, a machine that can chew on horrendous terrain while holding speeds for sustained periods of time.
Two years ago, KTM’s initial efforts proved that they had work to do. They tried building their Baja machine around the 530, and reliability proved to be a weak link. When Kurt Caselli decided that Baja was his next goal, KTM shifted serious resources into building a machine based around his National Hare and Hound-winning steed, but was fit with some additional safeguards for increased engine durability. The team dominated the San Felipe 250, proving that their wagon had the speed and durability and the team racers were gifted and Baja savvy. Following the Baja 500, where they finished third (Caselli was hurt, and Ramirez nearly destroyed the race bike early on), we got a chance to ride the full-factory race bike. KTM’s Anthony Di Basilio (head Baja tuner and Kurt’s mechanic) brought the machine down, along with racer Ivan Ramirez, for a test day at the rugged Stoddard Wells grounds. Here’s a look inside the full-factory race bike, along with input from Anthony and a personal view from our own Mark Tilley who got to ride the machine.
 
ENGINE: KTM North America gets these engines straight from the Austrian factory completely assembled. The only time they come apart is for maintenance or if they have major issues. They engine is tagged as the 450 Rally motor designed for KTM’s Rally race team. The motor is based off of the 2012 450 SXF twin-cam, carbureted bike. It’s fit with a Pankl rod and piston, has stock compression, factory cam timing and with some factory porting; grinding and flow mods produce what they deem as “optimal mid- to top-end power.” Internally, the clutch is factory stock, though there are additional oiling ports to help longevity. And, it uses a special Duval transmission, stock Del West valves, and older-model SX-wide radiators that are modified to accept stock hoses so that they can use stock radiators if something were to happen during the race. Engine Ice coolant, Motorex 10W-60 full-synthetic oil and VP T4 fuel handle the fluids.
ELECTRONICS: The ignition cover on this motor is specifically built to house the stator and flywheel out of a 350EXC machine. This has to be done so that they can run a headlight and taillight. This motor was never intended to run any kind of lights, so the stock components were made to run the bike, and that’s it. With the different stator and flywheel, Anthony had to fit up a bigger regulator. For this new weld, tabs are welded onto the frame in a new location. The wiring harness is altered, as Anthony extended some wires, changed a couple of connectors and made a harness for the lights. The first time he did this, it took an entire day to get it right. The CDI is off of the rally bike. The mapping in it is made for durability and controllable power. The CDI box they used for the San Felipe 250 was more like a stock bike, but the CDI for the 500 had the rev limiter lowered about 1000 rpm for more durability. Surprisingly, during testing, the San Felipe CDI box topped out at 114 mph, and the 500 CDI topped out at 108 mph.The San Felipe CDI rated way higher on the fun meter, pulling fast and hard through the power curve. It worked great in the whoops. 
EXHAUST: The exhaust is special made by FMF specifically for our motors. The header is made for better all around power and superior top end power for the long valleys and dry lakebeds across the desert. The mid pipe is also special made for greater power. The muffler uses a special heavy packing muffler that doesn’t blow out from sustained drama. Both the header and mid pipe are stronger than stock FMF systems to handle long-term abuse.
GEARING: 15-46. Top speed on dirt is 110-plus mph.
WHEELS: They run stock hubs with Excel A60 rims and stock spokes. This combination is very reliable for the desert and anything else the Baja terrain has to offer. 
TIRES: For the front, the team uses Dunlop’s 742FA with a bib-mousse insert. In the back, they run a Dunlop 739 Desert A/T, also with a mousse.
BARS: Renthal Twin Wall 999 bars (the McGrath bend) are used. Anthony removes the crossbar (this bar is very strong), and they fit up a GPR stabilizer that sits above the bar. GPR specially makes a top bar clamp, and a KTM Hard Parts rubber-mounted bar clamp is used on the bottom. Anthony modifies the front-brake lever, shaving it down for a skinnier feel (per Kurt’s request). Inside the bar ends, Anthony fits up Vibranators, which help to reduce vibration on the sections when the guys are doing 100-plus mph for 10 minutes or longer. Their hands would go numb without them.
CONTROLS: The team sticks with Brembo brakes, feeling that their power and feel are plenty good. Anthony changes the brake fluid to Motorex racing brake fluid. Up front the unit right off of an EXC model bike. It has a longer front brake line that is necessary to clear the headlight. The rear brake has a stock master cylinder and stock caliper. Out back, they fit up a Galfer brake line that is thicker and more durable than stock. Anthony puts a Chamfer on the brake pads that are also stock, so that during a wheel change, the rotor funnels into the pads much easier. A Motion Pro brake snake keeps foreign objects from ripping the brake pedal and shift lever off of the rally bike that was made specifically to clear the ignition cover. They modified the lever so that it can use a Hammerhead 20mm-plus tip so that the distance between the footpeg and shifter are the same as stock. This motor is out of the factory rally bike that uses a completely different frame, so their footpegs are in a different spot; this is why the tip is modified.
SUSPENSION: The WP Suspension on the Baja bike is the aftermarket kit suspension from KTM Hard Parts, and the components are made in the WP race department in the Netherlands. Up front, the front fork is the 48mm “cone valve” fork, which WP uses for Baja, WORCS, H&H, Enduro, SX and MX. This damping system gives the rider a more stable feeling than the regular shim-built damping systems. By choosing the shape of the cone (there are three to choose from) in combination with a spring (five choices), there are many options to adjust the damping for every kind of terrain or riders’ wishes. The positive character of the cone valve system is the stable character, but with a nice, plush, soft feeling, which all of their riders crave. Another positive point is the external preload adjustment for the fork spring that can be done in seconds. The outer fork tube is a version of the big-bore chamber tube that offers a smoother feeling and nice progressive damping at the end of the stroke. Together with the new developed oil, SKF low-friction seals, which is standard in 2013, Anthony believes that they have a strong advantage with this fork.
The shock is a WP Trax system shock. What that means is this shock provides better traction under slippery and dry, bumpy terrain. When the rear wheel comes loose from the ground, a valve opens and decreases the rebound damping, letting the shock travel quickly and getting the rear tire back in touch with the ground. When the rear wheel touches the ground, the “normal” rebound damping is activated. To change the preload of the spring, WP uses the XTrig adjuster, which is easily adjustable with a 8mm T-bar spanner, so no hammers are needed here. The spring Kurt uses is the 54-260.

 
 
 
 
 
 
 
 
 
 

DIRT BIKE RIDES THE
MISSILE!
It’s interesting to us that in spite of the entire world switching over to fuel injection (and that’s KTM too!), they’re racing the older carbureted engine. The number one reason is reliability. Dirt is the enemy of FI systems, and until they come up with a way to use a quick dump can and keep debris out of the system, they’ll stick with the carbureted, factory Rally motor.
Breaking down the performance aspect of the machine was a bit of a shocker. Why? Because it’s so rideable. Based around Caselli’s National Hare and Hound machine, the bike has to have the ability to throttle down and handle tight, rocky terrain without flaming out, or have stiff enough suspension to suck up an 85-mph G-out and chew on rocky bone sections without rattling your fillings into jelly. And the KTM’s suspension is completely stellar. The front stays up in the stroke, feels light, feels cushy enough and takes high-speed hits with a substantial appetite. The steering for a desert-designed machine is not only predictable, it’s precise, and the 22mm offset rids the machine of its normal understeer issues. Out back, the WP Trax shock is not only unique, it does an excellent job of getting rear-wheel traction. The quick rebound feel when the tire loses traction is odd at first, as it’s replaced with damping as soon as the tire touches down again. Once you get used to it, the feel quickly becomes useable and friendly.
Engine-wise, it hauls the mailbag quite well. Even with moon gearing and a five-speed transmission, the power that it blows out is smooth, friendly and heavily thrilling. It makes things happen, but it still feels like you could trail-ride it in spite of the fact that first gear is probably good for 50 mph. Tilley got it up to a sustained 114 mph! And that says it all; brilliantly fast and handles like a factory machine should: sharp, precise and just plain wicked.


Sponsor list: Bonanza Plumbing, FMF, Renthal, Excel, RK Chains, Trinity Graffix, Dunlop, GE Money Solutions, Twin Air, T.M. Design Works, Bulletproof, Motion Pro, IMS, Corona Motorhome Rentals, Zip Ty, Motorex, Rekluse, Thor, Acerbis, KTM Power parts, KTM Power Wear, WP Suspension, VP Fuels, Muscle Milk, Super B, and everyone at the shop

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WARNING: Much of the action depict­ed in this magazine is potentially dan­gerous. Virtually all of the riders seen in our photos are experienced ex­perts or professionals. Do not at­tempt to duplicate any stunts that are be­yond your own capabilities. Always wear the appropriate safety gear.

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