First Impression: 2005 KTM 125 SX and 250 SX

As new bike season approaches full swing, the TWMX testing staff’s latest day of riding was spent with the 2005 KTM two-stroke lineup. In a world that now seems dominated by thumpers, after spending a full afternoon roosting around Perris Raceway we’re here to say that two-strokes ain’t dead just yet!


Already heralded as one of the few remaining competitive two-cycles in its class, the KTM125 SX steps up to the plate in 2005 more ready than ever to challenge its four-stoke rivals. For starters, handling has been much improved thanks to an all-new frame and suspension package, which the 250SX also enjoys.


What’s different from the previous frames? As you may or may not remember, KTMs in the past have featured round, tube-like chromoly frames. This year the fame is still chromoly steel, but the big difference lies in both the added gussets and welds found throughout the frame and the all-new, oval-shaped tubing. The lateral, tubular design was meant to help out in front end stability when entering and exiting rutted turns, and all in all keeps the bikes more stable in the rough stuff.


The WP suspension is also new on both bikes. The fork has been redesigned altogether, and the SX lineup now features balanced inner and outer fork tubes that help keep the legs flexing equally for a better overall handling feel. Chrome-plated pistons were also added for less friction, and the forks have much better bottoming resistance than in years past. As for the shock, a modified piston rod and new shock body work together to offer improved damping characteristics and bottoming resistance. KTM’s goal with the setup was to offer riders better traction on acceleration bumps and an improved feel coming into harsh braking bumps.

Another cool feature of the 2005 models is that both bikes come stock with an adjustable-offset, aluminum triple clamp. What was once a popular aftermarket item is now standard equipment, and 2005 KTM riders have the luxury of choosing from either an 18mm offset or a 20mm offset, depending on whether they want tighter steering control or better stability at speeds. Trick.


If you think that just because there were substantial chassis changes made to the SX machines that the Austrian engineers slept on the powerplants, you’re dead wrong! Bigger crankshaft diameters, dual piston rings, a new cylinder and different carburetor settings all add up to make the ’05 250SX faster than ever. The 125 didn’t get quite as many modifications to its motor, but if you know anything about the little orange rocket, you probably already know that it didn’t need it!


Plenty of minor detail changes also abound in the 2005 SX collection, the most important being the addition of a stock front fender brace. Riders will no longer complain of the stock front fender slapping against the wheel during hard hits—the ’05 is as solid as a rock! New shrouds are also found on the 2005, as are vibration reducing, dual compound grips mounted to stock 1 1/8 aluminum handlebars.

Well, enough of the technical update crap, let’s get to it… On the track, both bikes showed tremendous improvement over last year’s models. Better handling was the name of the game this year, and the new frame is definitely a welcomed change. Both the 125 and 250 entered and exited corners and rough, whooped-out sections like they never have before. Our test guru Rich Taylor summed it up best by saying, “In the past, the KTMs have been so fast, motor-wise, that the chassis couldn’t keep up with them. This year, with the improved stiffness and rigidity, I can really take advantage of the bike’s strong powerplant.


It’s no secret that KTMs of yore were plagued by side-to-side movement in whoops and other extremely rough sections of the track—it’s been a thorn in their side for years. The stiffer frame of the ’05 has finally all but eeliminated this problem on both bikes, most notably the 250. The new suspension also helped out in the handling department, and our test riders raved about the updated forks, which resisted bottoming yet were still plenty plush in the chop.

Switching to the motor, as usual both KTMs are firebreathers. Though a bit sluggish off the bottom, once the power hits on the KTM125SX you better be holding on tight! Mid-range and top-end power is impressive indeed. After spinning laps on the 2005 YZ125 last week we thought there would be no competition for the blue tiddler this year, but the KTM has us second-guessing ourselves. As for the 250, it too was a little sluggish off the bottom with stock gearing, but once the power hits there’s plenty of it on tap. Mid and top-end power was as smooth and predictable as it was fast and useful.

Both two-stroke KTMs are the product of several changes and updates for 2005, making them the best orange bikes to ever roll off the assembly line in Austria. Considering the fact that we’re now only in the middle of July and barely into summer, the shootout wars are already shaping up to be some of the best ever. Keep your eyes peeled for the October version of TWMX, where we’ll have full tests of the 2005 KTM125 and 250SX models.

Want to see the KTM 125 SX and 250 SX in action? Click the video links on the upper right. To view the videos, you’ll need Quicktime 6.x, which works for both Mac and PC, is available as a free download at
125 Video Specs: Running time: 2:49.25/File size: 10.2 MB.
250 Video Specs: Running time: 3:17.07/File size: 9.3 MB.