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DIRT BIKE TEST: KTM 250SX–NOV 6

November 6, 2002
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DIRT BIKE TEST: KTM 250SX–NOV 6

(This test can be found in the December 2002 issue of Dirt Bike Magazine)


What?s on KTM?s mind? First off, the company signs Jeremy McGrath. Second, it unfolds a new 250SX that shares almost nothing with last year?s machine. The bike is completely new in the chassis, suspension, engine, ergos and performance. It?s gone on a diet, with weight savings and handling being the dominant themes. In fact, KTM even developed a new motor for the sake of handling?horsepower was never the issue.

KTM?s commitment to racing is obvious. By hiring McGrath and teaming him with the new 250SX, KTM people are chomping at the bit to spit out headlines. They want credibility, they crave results and they?re backing it up with new hardware. So with that in mind, let?s look at the 250SX.

THE SUM OF THE PARTS
The 250SX for 2003 is a completely redesigned bike, from the engine to the frame. The majority of the technical innovations came on the heels of the 250 GPs and were immediately implemented into the production bike series for the year 2003. Like we said, the biggest reason for the new motor was to improve the handling. Here?s how: the positioning of the crankshaft in relation to the vehicle?s center of gravity has been shifted in order to force more weight onto the front wheel. This also makes engine dimensions more compact and the frame shorter. The sum of these changes is all targeted towards making the front wheel stick better. By rigorously cutting the weight of engine components, the engine is smaller and far lighter than the ?02.

With a focus on weight reduction, the ignition, outer clutch and control covers are made of magnesium. The Boyesen intake introduced on last year?s model has been improved for the new engine. The five-speed transmission has been fully redesigned and is slimmer and more compact. Again, weight savings and size were the catalysts to change here. A new aluminum gear selector drum with narrower shift grooves targets smoother shifting under extreme loads. Plus, a new bearing roller on the gearshift fork minimizes wear and friction. The entire clutch package has become lighter and slimmer. The forged and milled clutch wheel was redesigned in order to reduce moving mass.

Thanks to a new plastic insert and a slightly lower crank weight, the new SX crankshaft is 100 grams lighter than the ?02, a goal to increase the engine response and power development. Also, a shorter connecting rod with identical-to-?02 bore/stroke means that the cylinder is now shorter and lighter. Same goes for the piston; it?s lighter as well. A new digital black box now features a throttle-slide-dependent mapped ignition system. So depending on engine rpm and throttle position, the optimum ignition curve can be achieved for improved throttle response. The Keihin PWK 38AG/TPS carburetor comes with a sensor for the throttle-slide position.

To fit with the compact new engine and the upright cylinder, the new frame of the 250 SX has been shortened by 15mm, which makes for a shorter wheelbase than the ?02. New steering-head gusset plates, various forged components, and a reinforced swingarm bolt contribute to the frame?s enhanced stiffness. As a result of the shorter frame, a 10mm longer swingarm was mounted on the bike.
A new one-piece rear end which integrates the side panels and rear fender makes for a slimmer and more ergonomic feel, and quick-release snaps facilitate the mounting and dismounting of the air-filter box cover. All SX models are fitted with a new modified front race number plate with integrated brake hose guide, and there?s a new seamless seat cover. All SX models will come with the White Power USD 48mm forks and will be equipped with a preload adjuster. This means the spring preload can be readjusted fast and easily on the outside. The new fork has three bearings per fork tube, which ensures better guidance of the inner tubes during compression travel. KTM also improved chromium quality of the fork coating to prevent excessive “pumping up” of the fork in use. The offset of the triple clamps was changed by 14mm (20mm last year) for quicker steering.
The WP PDS rear shock was modified considerably. A larger reservoir plus more oil volume targets premature fading. Altered valving concepts target better progression for the shock.

BIG ROOST
First things first. The KTM 250SX is an absolute rocket. It makes more power than any production 250 two-stroke we?ve ever ridden. KTM engineers say that the bike was actually faster in the prototype phase of development and they decided to tame it down. We can?t even imagine what that bike was like. The SX is pretty average at the very bottom of the powerband, then it comes on fast and hard. By the time it peaks out, your eyes are blurry, your arms are pumped and your head is about 200 feet behind you. Overrev is good, too, although there?s no need to scream the bike. All that and flawless jetting, too. The bike doesn?t ping, bubble, burble or miss. Those crazy Austrians have figured out power, that?s all there is to it.
Here?s the catch. Even with all the talk about making a motor that?s manageable, we have to say that the SX is still a handful. When you get tired, it gets harder and harder to keep up a good pace on the SX. You aren?t sure if you can handle the burst of power, so you just upshift and idle around the track. When you factor in an excessive amount of engine vibration, you have a bike that turns normal forearms into stone. The answer is to be so strong that you never get tired and you can use all that power. Sounds easy.

KTM LITE
You hear riders complain all the time about KTM handling. What they are really complaining about is that fact that it?s different from the last bike they rode. KTMs are kind of rigid feeling and have a distinctive, but benign, turning personality. The new KTM doesn?t feel dramatically different from the old one, but it is different from a Yamaha. The bike?s strong point is its weight?or lack of it. The bike is a feather on wheels. Previously, the lightest bike in the 250 class was the aluminum-framed Honda CR250R. But the Honda gained a pound for 2003, so at 217, the KTM takes the title. And on the track, you know the bike?s light. You can make things happen and correct for mistakes just by tossing the bike into any position you please. On the flip side, you feel like you always need to correct for something. The bike is busy.
In the suspension department, the bike hasn?t really changed that much. As with past models, riders tend to fall into two groups: those who hate the fork and shock and those who don?t mind the fork and shock. If there?s a third group?those who love the suspension?we haven?t yet discovered it. The bike does everything that it should do; it handles whoops and jump landings well and never does anything scary or unpredictable. It?s just not terribly comfortable along the way. Clicking the fork or shock to be softer is always the first response, but it?s not a soft/stiff issue. In the heat of a race, no one will fault the KTM suspension, and it won?t cost you any wins. But in the day-to-day riding and practicing that goes on outside of organized racing, most riders have issues.

BITS AND PIECES
* Of all our testers and staff, we couldn?t find one rider who cared for the new low flat Renthal bend. We ended up bolting on last year?s bend and immediately felt better. Still, the stock bar is of much higher quality than that of any bike from Japan. Kudos to the grips and Magura controls.
*The new SX is a much lower feeling machine than past efforts. Still, the saddle did not get rave reviews, as its still pretty stinkin? hard.
*The kickstart lever stuck in the down position (it kept getting stuck on the frame) and it took a little precision filing to fix it.
*As lightweight and high-tech as the numberplates are, they?re small enough that normal sized numbers barely fit. Also, the front fender scrubs the tire on compression and can be fixed by mounting up a KTM enduro fender brace.
*The hydraulic clutch is awesome. It works well when the engine gets hot and has good feel.

THE STUFF OF SUPERCROSS
We understand exactly why McGrath went to KTM. The bike feels just like any one of his works bikes that we?ve tried over the years. It?s crazy fast and super light. Comfort is secondary. For making a works competitive bike on a production level, KTM deserves to sell a ton of bikes. Sure, there aren?t thousands of McGraths out there, but maybe the 250SX will help create some.

 

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