2019 Factory Off-Road Bikes—RT Motorsports KTM 450 SX-F

RTM turns a KTM 450 SX-F motocross bike into a Baja racer.

The RT Motorsports KTM 450 SX-F Baja racer sits poolside 12 hours before lining up for the SCORE Baja 400 where it would finish fourth. It has a number of mods that make it better suited for long-distance desert racing.
The RT Motorsports KTM 450 SX-F Baja racer sits poolside 12 hours before lining up for the SCORE Baja 400 where it would finish fourth. It has a number of mods that make it better suited for long-distance desert racing.Mark Kariya

In an age of specialists, it's refreshing to witness a jack of all trades. While KTM's 450 SX-F is designed and marketed as a motocross racebike, it's proven to be well suited to other dirt applications as well, from flat track to off-road racing—with the right modifications, of course.

So, when it came time to build a Baja racebike, RT Motorsports (RTM) bought one and set about modifying it to suit instead of starting with an XC-F, which would’ve required changes anyway. Also, the 450 XC-F costs more to begin with. And as RTM principal Ray Dal Soglio (partnered with Troy Vanscourt) points out, “The motor and gearbox are actually the same [in both versions].”

Starting from the bottom, one of the first swaps is the wheels—specifically the rims and spokes. RTM feels the standard wheels just aren’t up to the high-speed abuse Baja dishes out, so a set of Warp 9’s Elite 7050 rims and spokes replace the stock items on OEM hubs. Naturally, an 18-inch rear is used.

“They’re a little bit stronger [than stock], but not too strong,” Dal Soglio points out. “You still want the wheel to [give] a little bit when you [have a] big hit, so those wheels have worked pretty good [in Baja].

“That’s one of the first things you’ve got to do with [Baja] bikes is relace the wheels because the spokes and rims that come on the KTMs are kind of cheesy; they just come apart pretty quick.”

RTM runs 15/48 gearing via SuperSprox sprockets and EK X-ring chain, resulting in a top speed of just under 100 mph on VP Racing 100-octane fuel.
RTM runs 15/48 gearing via SuperSprox sprockets and EK X-ring chain, resulting in a top speed of just under 100 mph on VP Racing 100-octane fuel. The BRP chain guide has proven itself very durable while the IMS Core pegs with Champion Adventures rear extensions give the rider added leverage and comfort. A modified Honda “floating” rear axle helps yield quick wheel changes.Mark Kariya

STI tires grace both wheels, Dal Soglio praising the new desert-specific Tech 2 Pro D. “Mark [Samuels] and Colton [Udall] actually helped develop it,” he reveals. “We did a rear tire change about halfway [through the recent Baja 400 where we finished fourth], but we ended up keeping the front on the whole race. The rear probably could’ve made it, honestly, all the way too. We’ve really been happy with them.”

Nitro Mousse Platinum foam inserts fill the STIs and have provided long life matching the tires.

RTM retains the standard Brembo brake systems at both front and rear, Dal Soglio declaring, “Brembo brakes are the best brakes on a bike. We’ve had zero issues with them. OEM brake pads, they last forever; we can run a whole race on [them] and there’s still life [on them] at the end of [a long SCORE race]. At the [Baja] 500 and [the Baja 400], the pads are halfway decent at the end of the race and we end up using them on our prerunner after that.”

Interestingly, Dal Soglio confides, they use a modified Honda “floating” rear axle in order to make it easier to run fixed axle blocks for quicker wheel swaps. “That’s an old trick from the Honda days,” he muses.

Suspension is WP with a combination of AHM valving and a Dal Soggio fork kit to make it a coil-spring fork. Warp 9 rims and spokes on stock KTM hubs are must-haves in Baja, according to RTM.
Suspension is WP with a combination of AHM valving and a Dal Soggio fork kit to make it a coil-spring fork. Warp 9 rims and spokes on stock KTM hubs are must-haves in Baja, according to RTM. The Baja Designs Squadron headlight is on during the day for safety.Mark Kariya

AHM Factory Services handles RTM’s suspension tuning, converting the standard WP Xact air fork to one using 4.6 N/mm coil springs with a Dal Soggio kit from Italy and opting for slightly lower air pressure than standard in the bladders for better initial compliance. “The [Dal Soggio] kits are also auto-bleeding, which is nice because the fork will bleed itself throughout the race,” Dal Soglio notes.

In back, AHM also revalved the standard WP Xact shock for more liveliness in the initial stroke to better absorb small, high-speed chatter and employ more of the travel. However, what may have had the largest impact on performance is the Pro Circuit linkage.

“It changes the angle of the shock and has it working a lot better,” he insists. “The bike’s a lot more balanced with that and makes a big difference. I don’t know the spring rate [now] because the linkage makes it go up a rate. I think we’re two up from stock."

There aren’t many complaints about the standard 450 SX-F’s power, so changes are minimal. A Pro Circuit Ti-6 full titanium exhaust system and Blais Racing Services mapping make the most difference.
There aren’t many complaints about the standard 450 SX-F’s power, so changes are minimal. A Pro Circuit Ti-6 full titanium exhaust system and Blais Racing Services mapping make the most difference. Also seen here are the Seat Concepts Comfort-model seat and STI’s Tech 2 Pro D tire with Nitro Mousse Platinum foam insert.Mark Kariya

A full Pro Circuit Ti-6 titanium exhaust system is one of the sole changes to the engine, which also retains its five-speed close-ratio gearbox—for now. As Dal Soglio says, “We might be getting a six-speed for the 1000.

“The bike with a five-speed, we run 15/48 gearing on it [and] the bike will do just shy of 100 miles an hour, so we get plenty of speed out of it.” SuperSprox sprockets and EK gold Quadra X-ring chain get the nod here, the chain guide a BRP item. While the clutch cover is from Rekluse, the actual clutch assembly is standard KTM.

He adds, “We actually keep the motor stock just for reliability. The engine puts out so much power [as is], you really don’t need to do anything to it.”

“The only [significant] thing we change is [going to] an EXC ignition, the stator and everything. That allows us to make 200 watts and allows us to run [added] lights [for the Baja 1000], the big Baja Designs lights on the bike. It’s all OEM parts—we change the ignition, ignition cover, the stator, and everything.

“The one thing we change is the mapping on it. We have Chris Blais [of Blais Racing Services] do some mapping for us. He kind of mellowed out the bottom a little bit. He set it up so it runs a little richer than normal because when you’re going fifth down a road and pinned for a while, you want to make sure it’s getting enough fuel. He has a setting for Baja that makes smooth, linear power; it’s not too aggressive on the bottom just because out in the desert we don’t need that—we need more smooth power. We get a little bit better gas mileage with the mapping that we have too.”

With the Blais Racing Services mapping, range with the 3.2-gallon IMS tank is about 75 miles, though the team locates pits more conservatively in the 60-mile or so vicinity.
With the Blais Racing Services mapping, range with the 3.2-gallon IMS tank is about 75 miles, though the team locates pits more conservatively in the 60-mile or so vicinity. RTM feels the low-bend Tag Metals handlebar is ideal for KTMs while the GPR steering stabilizer is practically standard issue for high-speed desert racing.Mark Kariya

Happily for the team, that means close to 75 miles out of the 3.2-gallon IMS tank (with dry-break quick-fill receiver, of course, as well as a metallic heat shield glued to the front to ward off heat from both the radiators and engine so as not to heat the fuel). By comparison, Honda teams have traditionally employed a 50- to 55-mile distance between pits on pre-fuel-injected bikes.

However, to be safe, RTM doesn’t push it that far. “We try to [place pits] every 60 miles so not to take any risk,” Dal Soglio shares, the bike gets filled with 100-octane VP Racing fuel at each pit.

To bolster the sometimes vulnerable radiators, he says, “We have custom fabricated radiators that have been braced and welded for strength. We’ve had bad experiences [with non-strengthened radiators] down here.” A bit of wire mesh safety-wired to the front of the radiator’s plastic louvers also adds a bit of protection from minor intrusion.

A P3 carbon fiber skid plate shields the engine from much Baja abuse as well, though the team hasn’t seen a need yet to guard the brake rotors. FCP Racing engine mounts replace the stock items for the improved chassis feel RTM likes due to targeted frame flex characteristics. IMS Core Enduro footpegs provide a wider, more comfortable platform than stock, but these also incorporate a triangular extension off the backs developed by Colton Udall’s Champion Adventures.

“Basically what that does is give you extra leverage like in desert races where you’re standing and hitting whoops [for a long time]; it gives you a little bit extra support,” Dal Soglio says. “It also gives your calves and muscles a little bit more of a break when you’re doing long stints. It was something Colton came up with, and [when] we were testing it, every rider said they really liked it.”

Also improving comfort is the Seat Concepts “Comfort” seat. It maintains the stock height but has dual-density padding (softer on top and denser bottom). “It’s a little bit wider, too, in the back so you sit on it a little bit better [compared to the narrower seat that KTMs come with]. It makes a huge difference for long races!” he declares. “The foam density is pretty nice; it takes some of the vibration and impact away while you’re racing compared to a stock seat.” There’s also leather-like material on the sides to aid in gripping with the rider’s knees as well as increased durability.

DT1 air filters on stock cages take care of debris before doing any engine damage, and Maxima lubricants and fluids are used throughout. A Tag Metals T2 low-bend handlebar rides in a BRP top triple clamp (the bottom is stock KTM) and bears A’ME grips on both sides. RTM uses a GPR steering stabilizer behind a headlight shell featuring a Baja Designs Squadron LED headlight, which is primarily a safety measure. When it comes to extended night sections as found in the 1000, this will be replaced by larger Baja Designs lights on a specially fabricated mount welded to the steering head. Lastly, graphics are from ZLT.