Driving report KTM 450 SX Racing

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Driving report KTM 450 SX Racing

Model X

The year X is approaching. From the 2003 season, 450 cc will become the magical size in motocross. The manufacturers are upgrading enormously? KTM too.

It was a great success, the launch of the 450 SX Racing at the second meeting of Germany’s most prominent motocross series, the DMX at the end of July in Bremen-Hoope. Three runs, three wins. Achieved by ex-world champion Joel Smets himself. And because he even kept the flagship crosser Pit Beirer down in second place, this triumph at the premiere was even more important.
That’s good, because the new one is important for KTM. As an image carrier for the future first class of the motocross society. The new league will be called 250 cm3 two-stroke / 450 cm3 four-stroke from the 2003 season – and the 450 cc four-stroke will dominate the scene. That is why we are upgrading. Honda has already set the bar very high this season with the elaborate new design of the CRF 450 R: straight away the victory in the MOTORRAD comparison test (issue 26/2001) ?? also against the bigger sister of the new orange, the KTM 520 SX. Yamaha, a trendsetter since 1998 with the YZ 400 F and YZ 426 F in this category, is fighting back with the completely turned inside out YZ 450 F (see page 60).
And the 450 SX feels the pressure of the high-tech competition. Because one thing is clear: the 450 will only be competitive if the SX line’s tried and tested, but simple engine concept is used to the maximum. The main objective: easy turning. Not easy to achieve with a conventional ohc valve train. Feather-light titanium valves from the American Formula 1 supplier Del West, a stroke shortened from 72 to 63.4 millimeters and the 41 series Keihin flat slide carburetor (instead of the 39 series of the 450 series enduro) form the basis for sharper wind in the crankcase. E-starters are there ?? like everywhere ?? only for the enduros. No problem. A kick is enough, the SX 450 chugs away. Click, first gear is sitting. It is translated long because the six-speed gearbox has given way to a four-speed gearbox. But it doesn’t matter either, because the previous first gear remained unemployed on the cross piste anyway.
The first straight. First of all, take it easy. Switch through. No problem, as usual from the KTM crossers. Everything moves as light as a feather. Also the hydraulically operated clutch ?? one finger is enough. Even for braking. The Brembo double piston stopper on the front wheel has long been world-class. At the rear, the single-piston system also manages it easily.
Finally, man and machine are warm. Elbows up, head forward, attack. The moment of truth is approaching? Or should we say a first estimate, without the barometer of the red and blue competition. First the tight 180 degree bend. Brake, second gear, bend and let the clutch come with a lot of gas. Indeed, the SX 450 goes off. No comparison to the current 400, purely subjective but also without the powerful punch of a 426 Yamaha or the brutal acceleration of a 450 Honda. Efficient for sure. Loose ground or hard terrain with little traction? What the hell. Cut traces? No problem. Just open the tap and full throttle. The 450 pulls through cleanly, does not flip across, does not break out maliciously. Don’t stress more than absolutely necessary. Why are there no more 40-minute races??
The following straight is long. At 10700 rpm, the rev limiter is said to be the act of grace. But the single hardly turns up that high. Gradually, even before this limit, his breathing becomes flatter, he shyly warns: Shift up! And you do it, because then the single cylinder presses again where it likes to press ?? in the middle speeds.
Is ?? by the way ?? also clearer when downshifting. When the deceleration increases, crossers usually have their hands and feet full anyway. It’s good when the fork runs as cleanly as the new 48 from White Power in the bad brake waves. The new sealing and dirt scraper rings of Japanese origin and the three cylinder liners do a great job. Nothing gets stuck, nothing sticks. And if it ?? if the table top has jumped too far, for example – if the going gets tough, the hydraulics save the situation with well-coordinated progression and a buttery-soft end stop. Selected pieces or factory forks have already achieved this so far. Now all KTM drivers should finally benefit from it. At the rear, the tuning of the shock absorber, which is directly linked to the swing arm, fits better from year to year.
D.Nevertheless: The thoughts revolve around the engine again and again. Is man fallible? Does the single feel slower than he is? Can 500 grams be too much? Because the rotor weighs exactly one pound as it rotates as a flywheel on the right-hand crankshaft stub. Let’s do the test. Housing cover down, rotor unscrewed, a few more laps. The 450 revs up noticeably more lively. And feels faster, looks more powerful from tight turns. But the search for traction becomes more difficult, and the rear end is much more restless on loose terrain. Faster on one lap? May be good. Faster over a half hour race distance? Not without top condition. The ideal might be 250 grams of flywheel. There is still room for experiments. Just turn it off and try it? later.

Technical data – KTM 450 SX Racing

Engine displacement increased to 449.4 cm3. Bore and stroke changed to 95 x 63.4 mm compared to the Enduro version (89 x 72 mm). Valves made of lightweight titanium, the valve springs are also lighter. The maximum speed could be increased to 10,700 rpm. The inlet cross-section increased from 39 to 41 mm. Motor housing is now manufactured using die casting instead of sand casting. Weight saving: 500 grams. Six-speed gearbox replaced by four-speed gearbox. Both exhaust manifolds are ?? for better passage – merged into a single tube directly after the outlet. ChassisNew 48 mm upside-down fork from White Power with improved sealing and dirt scraper rings as well as three instead of two bearing bushes and a thicker (26 instead of 20 mm) front wheel axle. Diameter for greater rigidity (52 instead of 36 mm at the front, 64 instead of 48 mm at the rear. Suspension strut with enlarged expansion tank. Air filter box enlarged by twelve percent. Rear fenders and side number plates form a unit.

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