When I first saw spy photos of the 2007 KTM 450 SX-F last year, I loved the radical look and cutting-edge thinking that went into the design. I especially liked the idea of dropping the kickstarter for the magic button on the handlebar. So in spite of the fact that I have never really favored KTM motocross bikes (though I love the EXC and XC off-road bikes), I lobbied to take the new 450 SX-F for the year to see if I could turn it into something I would look forward to riding on a regular basis.
I first rode the bike after our 450 shootout (March '07), when it already had about 20 hours on it. I loved the way the KTM made power (smooth bottom but plenty fast). It turned pretty well, but the fork felt really harsh. I tried moving around clickers and resetting the sag but couldn't find any adjustment that solved the issue. The harshness, though less noticeable while I was play riding in the desert, was still a problem. A second trip to the track and more fine-tuning left me with a sore wrist and very little fun! It was time to look into modifying the suspension, and I sent it out to MX-Tech (815.936.6277, 877.850.5114; www.mx-tech.com).
The suspension came back with some impressive tuning instructions, which I found very educational. MXT's modifications included fairly traditional valving changes in the fork, but a completely different theory was applied to the shock. Dubbed Constant Liner Progression (CLP), the shock's PDS needle is replaced for a more linear progression in the damping that is also softer at any given point. This is combined with a progressive rather than straight-rate spring (PDS #6 for my 165-pound Vet Intermediate riding level). The MXT crew has done a lot of testing and analysis and feels this is the best way to match the performance of a linkage suspension system, and they recommend 105-110mm of sag, so that is where I started. MXT kept the standard 0.46kg/mm fork springs. After looking at all of this data, I couldn't wait to get to the track.
Even on Cahuilla Creek's smooth MX track, it was very obvious that the MX-Tech mods had transformed this bike. This became more and more evident as the bumps got bigger. The bike is way more fun to ride. I can confidently hit square-edged bumps and jump faces without worrying about the rear kicking sideways, and the fork feels much more compliant in both small bumps and big landings. It still corners really well, and I found that I could better use the 450's power. I had installed a Ready Racing Rapid Response carburetor fuel-pump actuator arm during one of my previous trips to the track. Now that I could ride the bike harder, I was able to really push the limits of throttle response, and the actuator arm does seem to help.
Running TallyHours on Bike: 32.8Modifications: $887.93Ready Racing Rapid Response carburetor mod: $99.95MX-Tech suspension modifications: labor, $158; MXT WP 28mm piston, $175; MXT WP 50mm piston, $175; MXT NV '07 PDS needle, $149.99; MXT PDS6 spring, $129.99Maintenance and Repairs: $16.13 (not including tires)ProTaper half-waffle medium grips: $9.99Oil change with Maxima Maxum4 Premium oil: $6.45 per qtBridgestone M402A 120/80-19 rear tire: $117.66