Fixing The 2011 KTM 450 SX-F – Dirt Rider Magazine

By: Editorial Staff

Wednesday, April 13, 2011

/></a> <p class="wp-caption-text"></p> </div> <p><strong>I don’t consider myself a big guy, but after hearing it uttered by a few people, I jumped on the scale and realized the Dirt Rider crew was laughing at me and not with me. I am 6 feet 1 inches tall and 205-ish pounds in my birthday suit. There is a reason I find myself behind the camera instead of in front of it. After riding most of the 2011 450s, I was drawn to the KTM’s amazing power and long, extending top-end. Although I liked the bike, I knew it desired some fine-tuning that catered to my girth and riding style. The goal was not to change the bike, but to give it a little massage in the right places. I was forced to go riding at several tracks before crafting a grocery list of solid fixes and items to place in my shopping cart. Except for one outside service, all of the work can easily be performed with standard tools and a tad bit of mechanical aptitude.</strong><strong>Engine</strong><br /> The KTM is the last of its kind-carbureted. After riding FI bikes for the last two years you forget how quirky carbs can be, meaning bogs, slight hesitations and finicky fuel screws. I realized that weather changes really had an effect on the lower circuits and how the bike reacted at zero to one-quarter throttle. The carb already had a finger-adjustable fuel screw when I got my paws on the mount, and I took that a step further by adding a Boyesen Quickshot 3 adjustable leak jet. The two mods are not bolt-on-and-leave items; they have to be dialed in when conditions change. The combo was a blessing when the California weather jumped around between 95 and 65 degrees. Depending on the conditions, I had to twist the two adjusters around 1 to 1.5 turns in either direction. These adjustments can be made in seconds with a screwdriver and/or two digits.I wanted the versatility of a spark arrestor, maybe a little bit more low-end roll-on power and possibly shed a pound or two. Because the stock header is made of titanium, we opted first for just a slip-on unit. The FMF Factory 4.1 RCT is new and every system includes a spark arrestor, and it is a pound lighter than stock. The muffler alone without the S/A does give the bike a little more snap with regard to throttle response, yet performance changes were unnoticeable to this mule. We tried an FMF Megabomb header matched with the muffler, and it did help improve some low-end chug but does add to the cost of the overall build.<strong>Ergonomics</strong><br /> The bulk of the attention catered around fitting the bike to a taller, bigger and more stubborn dude. For this fix I went with a ProTaper EVO Henry/Reed bend and flipped the bar mounts around and put them in the forward position. I also ordered ProTaper footpegs because they were wider and offered optional -5mm cleats. When the shorter cleats were installed, they were only 1mm or less lower than stock. The fix for this was a KTM Powerparts 20mm taller seat.<strong>Handling And Suspension</strong><br /> The balance of the suspension is good stock, but the bike developed fork bottoming issues the harder I pushed it. The KTM boys suggested first installing a 6.0kg shock spring and increasing the fork oil capacity by adding 10cc of 5w fork oil to each fork leg. These changes made a big difference and helped improve the fork in the latter part of the stroke and held the rear end up while still running 108mm of shock sag. A shock spring and oil are worth testing before heading directly to a suspension shop for a full redo.I looked to Factory Connection for more help. FC altered the shock and fork valving and installed FC bottoming cones and a low-speed valve kit in the fork. The shock also got a reservoir bladder kit, a one-piece seal and a new high-speed valve component. Right from the get-go FC fixed my biggest issue-fork bottoming-and restored my confidence. The new valving did change how the bike reacted in some areas compared to stock, and it took a few sessions to adjust to get things fully dialed in. I opted for the stiffer of the two valving setups I tested since it catered to my style and modest girth. In the end, the bike was more stable charging into rough sections, felt like it was able to ride a little higher in the stroke, and harsh fork bottoming was no longer an issue. It could be a tad bit more compliant on the little chop, but I think that can be tuned out depending on the track. <div><a href=/></a> <p class="wp-caption-text"></p> </div> <p><strong>Miscellaneous Mods</strong><br /> Pretty much every other mod done to the bike has a function to some degree. Take the KTM PHDS Progressive Handlebar Dampening System (aka, rubber-mounted bar clamps). I have always run some sort of rubber bar mount and love the added flex of a ProTaper bar.I installed a Twin Air Powerflow cage and filter to perform a little idiot proofing. It’s possible to put the stock cage in the wrong way and/or leave an open area for dirt to get sucked into the engine. The Twin Air system uses an aluminum cage that almost locks into position with a flame-resistant filter.I installed larger billet Ride Engineering fork compression adjusters since my Neanderthal fingers are too fat. Bridgestone M403 and M404 tires are great all-around intermediate tires that cross over to other conditions very well, especially when new. The stock sprocket’s teeth were bent over further than the shark’s in Jaws. So Drive Systems answered my call with AFAM cogs and a shiny gold D.I.D chain.I had to toss a new coat of paint on the revamped machine. ZLT did the design and also a number kit, but those were left off because the Catalina GP race provided numbers. I did put on grip tape frame protectors from KTM to cover up the missing paint on the frame.<strong>Final Bits</strong><br /> Not that I am gargantuan, but it is nice to know that if you need a taller bar, higher seat, lower pegs and firmer suspension, these tools are all available. For this vet rider, the few personal changes turned the Katoom into a well fitting and easily-to-tune glove, not to mention the bike helped me garner a podium finish at the Catalina GP.<strong>Parts List</strong></p> <p><strong>Factory Connection:</strong> <a href="" rel=”nofollow” onclick="javascript:window.open(www.factoryconnection.com
Fork and shock revalve: $360
Parts and oil: $355.70
Boyesen Engineering: www.boyesen.com
Quickshot 3: $119.50
FMF Racing: www.fmfracing.com
Factory 4.1 RCT muffler: $374.99
Twin Air: www.twinairusa.com
Powerflow kit: $149.95
ProTaper: www.protaper.com
Evo handlebar: $89.99
2.3 Platform pegs: $179.95
Bridgestone: www.bridgestone-firestone.com
M403, 90/100-21: See your local dealer
M404, 120/80-19: See your local dealer
KTM Powerparts: www.ktmusa.com
PHDS Progressive Handlebar Dampening
System: See your local KTM dealer
High seat, 20mm: See your local KTM dealer
Frame decals: See your local KTM dealer
Ride Engineering: www.rideengineering.com
Fork compression adjusters: $44.95
Rubber-mounted bar clamp: $99.95
ZLT Graphics: www.zltmxid.com
Complete graphic kit with numbers: $180
Drive Systems USA: www.drivesystemsusa.com
AFAM 52T rear sprocket: $67.95
D.I.D ERT 520 chain: $136.80
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