KTM identifies and targets niche markets. The company defies rules or class structure and in the process sets trends while speculating forward. But KTM has also found success in redeveloping classes of bikes that may be falling from grace. It updated its large-displacement two-strokes when other companies stagnated, and now two-strokes in general are corporately ignored. So which maker is bringing out an all-new 250cc two-stroke motocrosser for 2007?
It shouldn't surprise you that this bike is good. These days all bikes are good; it's how good that matters. And measuring the "goodness" comes in two steps. First is riding the bike, getting used to it, dialing it in and pushing its limits to feel when it excels and where any weaknesses lie. Then you must compare the bike with others in the class. In this case, the '07 YZ250, Yamaha's update of Dirt Rider's '06 250cc two-stroke champ (see the Dec. '05 comparison).
The bulk of the KTM's changes center around the chassis, suspension and plastics, all of which are derived from the '07 SX four-stroke line. The frame is essentially the same top and rear sections of chrome-moly, with the lower cradle modified and tuned to accept the smaller, lighter 250cc two-stroke engine. Look at all that room above the cylinder. It appears you could do a top end without taking off the gas tank! The suspension components are the same as the SX-F's but with different settings. The plastic differs only in the airbox's attachment to the carb. This bike looks light, and the scale confirmed it is 210 pounds with no fuel in the tank. The engine didn't go unnoticed. It earned a more compact, 1.1-pound-lighter cylinder and head, in addition to a new power-valve governor assembly with improved timing control and second gear with a lower ratio.
Instantly, you will feel how light the bike is. Loading, unloading and just in moving it around, we found it noticeably lighter than any 250cc-or-over four-stroke; it brings up memories of 125cc bikes. That weight, or lack of it, draws attention in more ways than just feeling feathery while riding. The SX has a bit of vibration that's most noticeable during the first seconds on the bike. A little two-stroke tingle quivers through the bar and pegs. Getting some silicone on the pipe/cylinder joint and keeping the mounts tight work wonders. On the track, the SX, like most two-strokes, is a little dancey everywhere-the calling card of light weight and little internal rotating mass. Unlike a four-stroke, it skims across chop and bumps and feels like it skates through the bumps without ever planting the tire into one. Anytime either wheel bangs the ground, the initial hit transmits more sensation to the rider than a four-stroke would. The feel is like running more air pressure in your tires.
This light feel encourages more aggressive jumping and antics in corners. You quickly realize this KTM has an uncommon knack for turning that isn't familiar to the Austrian brand. There is a high degree of steering precision and a lot of stick. Overall, it's one of the best bikes we've ridden on choppy bumps when traction was plentiful. Blessing this feeling is the layout of the super-adjustable cockpit. It makes the SX easy to move around on and offers plenty of knee grip without ever being wide. The rear of the seat is low and allows you to get back over whoops-or when panic-revving off a mistimed jump. You can get as far forward as needed and there isn't much in the way of obstruction.
Suspensionwise, the KTM is similar to the 450 SX we tested last month. The re-angled PDS shock has a wider degree of setup flexibility with a more progressive leverage ratio. Sag needs to be between 107-112mm. If there is a downside to the no-linkage rear end, it was that fast or heavy pilots were using too much stroke on aggressive jump takeoffs. Most likely they are candidates for a stiffer-rate spring. Even with the shock set at 25 clicks out on rebound, the rear looked slow to return, so we went out two clicks and found the bike was happier.
WP forks take a little time to break in, and the new sealed-cartridge model used on the SX seemed harsh to a lot of riders. We started by reducing the compression, but ended back at stock after a few rides. We also found that tuning the rebound was helpful for finding the right cornering feel. Faster riders benefited from 10cc additional oil to ease the bottoming feel. KTM recommends changing the fork fluid early since the spring contaminates the oil in the first few rides. Fresh oil can help give better feel and movement. Learn to use the clickers on this bike and it can really pay off, especially at different tracks.
The engine has definitely undergone a power shift via lowering and smoothing the surge and meat of the delivery. It still has a slightly lazy characteristic and a normal two-stroke idle with an early pull. From idle on up, the motor is very smooth. It has a strong midrange and then it screams, especially after the bike has some time on it. We woke up the bottom when we dropped the pilot jet from a 45 to a 42. Good torque is available from this engine at all times. It feels like it is winding up a big rubber band, and it is easy to unleash the spring effect with just the throttle. Clutch effort is nicely light and not really snappy. Its engagement is long and very controlled and never like a light switch. On the track you get used to added lever travel, and on a start you can literally just drop the lever and launch. It is that smooth. The 250 SX's brakes are just the opposite. They are strong to the point of being touchy and take plenty of getting used to, especially the front.
Where does this goodness put the new KTM? Well, it is the best two-stroke MX bike KTM has ever built, and it makes the old bike feel sluggish, heavy and a little vague handling. It is a huge step up, something we've found to be common in every '07 SX we've ridden this year. But the company won't be satisfied with anything but being the best. At the same time, it tries to improve and raise the performance level of motocross bikes up a notch. So to truly find out if the 250 SX is a success, we lined up the '07 KTM against the new '07 Yamaha YZ250 for a shootout. You'll have to keep turning pages to get the full skinny.