Compared to past KTM SX-F models, this '08 has more snap and a bigger hit. Compared to Asian models, the power builds smoothly with energy increasing in an immediate relationship to rpm. The harder you twist, the faster it goes. Something about the relationship between the power, the rear suspension and the chassis geometry just works, and the KTM hooks up and accelerates hard. Sometimes it even carries the front all the way around turns when you aren't even trying. This isn't the tear-your-arms-off sort of fast, but there's plenty of power here for any sane moto person.
The chassis is generally well-mannered. The new frame design and shock placement introduced in 2007 is much sturdier than past KTM efforts. Not that frame breakage has been an issue, but under severe loading, the chassis would kick to the side. The '07 chassis design and '08 suspension settings eliminate the tendency. There's nothing new about the chassis for '08 but the suspension settings, but it still works well. effort at the bar required for direction changes. On any bike it can be difficult to separate the handling from the suspension, but it seems especially true here. Riders who got along with the suspension also found the handling agreeable. Pilots who took issue with the suspension were more likely to find the front end busy.
Some riders found little to criticize with the chassis or suspension, while others were never able to come up with a setting that they could call plush. WP declared war on stiction and revised the seal head in the shock, and worked on seal and bushing drag on the tubes and the cartridge in the fork. In addition, the spring rates are up front (0.46 to 0.48 N/mm) and rear (6.6 to 6.9 N/mm), the valving is fine-tuned and the shock has more low-speed compression and less high-speed. The suspension action is actually very good at keeping the wheels following the ground and the bike under control. Some would argue that means the suspension is good. Others would say that rider comfort is the measuring stick by which to judge suspension. The SX-F suspension gives a lot of feedback about track conditions, and you feel it as jolting to your hands. We felt the jarring to the hands at all tracks, but even on a brutally rough day at Glen Helen the bike tracked straight, never swapped and kept the wheels on the ground and driving. We saw the same thing with the 250 SX-F. Riders felt a lot of track, but the lap times were right on the money. Turning is crisp and accurate, with only a light Controlled? Absolutely. Plush? Not for most riders. We could never narrow down the suspension issues, either. It wasn't all heavy guys or all aggressive riders. Some had issues but other riders the same speed, weight and height disagreed.
Much has been made about the fact that the KTM rear suspension has no linkage, but the front is most often criticized. The rear now has a good range of adjustment, plenty of bottoming resistance and good control. After you live with the KTM system, you'll be reluctant to revert to the maintenance and complexity of a linkage. The KTM has two other flaws. One is a seat that is thinly padded and constructed with soft foam-not a good combo. We have noted a variety of seat density from bike to bike. If you get one with firm, dense and resilient foam, the stock seat is fine. Otherwise, it isn't that comfortable. Second is that throttle response at small openings can grow fluffy as the engine heats. We are certain the problem lies in accelerator pump settings, but we never found a surefire cure.
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KTM created the 450 SX-F with plenty of motor. The electric start does not add any heavy feel. |  |