This is the 2010 KTM 450SXF the way the MXA test crew raced it. As a rule, we don’t go for exotic or expensive mods, but if push comes to shove, we will seek competent help (no matter how much it costs). Use MXA’s mods as a guide.
We don’t know where KTM found a stockpile of old-school Bridgestone M59/M70 tires, but we find them acceptable. The M59 front is much better than the Dunlop 742 that comes on many other bikes. If we were the product manager at KTM, we’d be looking at spec’ing the bike with Bridgestone’s M403/M404 combination for 2012 )They willhowever be putting Dunlop MX51 tires on the 2012 models...and Pirelli's on the two-strokes.
Carburetor: Most MXA test riders love the feel and response of Keihin FCR carbs. That said, we still try to maximize our ability to fine-tune the carb by adding an R&D Flex Jet and Power Bowl (www.r1dean.com) to gain not only an adjustable fuel screw, but an adjustable leak jet. The 2010 KTM 450SXF is the first 450SXF to get a leak jet.
Forks: The KTM’s 48mm WP forks are well-damped and well-sprung for everyone except fast pros. They come stock with 0.50 kg/mm fork springs and an acceptable oil height. If you bottom over big jumps, add 5cc of fork oil through the air bleed hole. If you want them softer, drain 5cc out of the same hole. These are the best WP forks in KTM’s arsenal and can be made better with a revalve.
Subframe: Even though KTM lowered the frame by 10mm and shortened the shock by 4mm (which lowered the rear another 10mm), we cut the subframe down by 4mm more to bring the rear of the KTM 450SXF even lower. Getting the chassis flat allows a lot more tuning possibilities for both fork height and race sag.
Every MXA test rider chose to replace the stock 7.2 kg/mm spring with a stiffer 7.6 kg/mm spring. This was a big improvement for riders above 175 pounds. We have tested Fox, Ohlins, Race Tech, Showa and stock WP shocks. We like the Ohlins (www.ohlinsmx.com) shock best (with a 7.5 spring), but on a practical note, we think that the stock shock is very good (with the correct spring).
We clipped the gas cap locking tabs off to eliminate the locking capabilities. If you do it just right, the gas cap will still click on, but will come off without pushing the button. In our experience, the locking tabs can stick to the point where the gas cap can’t be removed. Cutting off the tabs with dykes ensures that this won’t happen, even on the muddiest days.
To maximize the thrust of the new five-speed gearbox, we add one tooth to the rear sprocket for tight tracks, but thought that stock was best for bigger and faster tracks. Although the KTM 450SXF is blazing fast from the middle on up, it has a very steady and metered low-to-mid power output. Gearing it down perks up the power from 5000 rpm to 7500 rpm. After 7500 rpm, the KTM doesn’t need any help.
Rear fender: We cut the rear fender/side panels away to make room for our hands to get between the exhaust pipe and subframe. This makes the bike easier to lift. It is
easy to do—just make sure that you leave the plastic part that the
subframe plugs into. The 2011 KTM's come stock with room for the rider's hand.
Favorite exhaust pipe: Our favorite 450SXF pipe is the DR.D exhaust system (www.dubachracing.com) because it has a unique look and broadens out the middle. The stock KTM 450SXF pipe gives up some horses over a few years ago in the name of sound reduction.
Chain guide: We replace this stock KTM chain guide with a TM Designworks all-plastic chain guide. It is bulletproof. www.tmdesignworks.com