Bikes 31 Aug 2012

Tested: 2013 KTM SX-F range rides the all-new 2013 model 250 SX-F, 350 SX-F and 450 SX-F at Louee’s Aussie launch.

You have to admire KTM’s unrelenting surge toward the top of motocross worldwide. As the reigning world champions in both MX1 and MX2 following title-winning campaigns by Antonio Cairoli and Ken Roczen respectively, KTM set out to do likewise in America.

Now, thanks to Ryan Dungey’s signing and an awesome new 450 SX-F, the Austrian brand just won its first ever American Motocross Championship in the premier class. Add to that the fact that Dungey had already won KTM’s first 450 supercross this year and it’s easy to see that it’s been a top 2012 season.

When KTM signed Dungey, it released a special ‘Factory Edition’ 450 SX-F in the US (read a review on MotoOnline by clicking here) to meet regulations. The bike was a roaring success and what he has raced all year, but for 2013, it’s basically become the base of KTM’s SX-F range.

KTM shares many components between its range, including the vast majority of the chassis, and it’s all come about direct from the racing teams competing around the world, more specifically in the US. The 450 SX-F is the big news, hot off the success of Dungey, however the 350 SX-F and 250 SX-F certainly haven’t remained untouched. got our first taste of the 2013 range at KTM Australia’s official press intro this week, held at the popular Louee Enduro and Motocross Complex near Mudgee in New South Wales. With three highly anticipated bikes and a first class crew on hand to help us from KTM, it’s days like this that us moto journos dream about!

First up I was scheduled to test the 250 SX-F, which has five additional horsepower compared to the 2012 model – which we had been lucky enough to feature as our Project Moto long-term test bike this year. Needless to say, I was interested to witness the improvements after I could sense KTM’s excitement in the model.

On track the power is definitely noticeable. The mid-range and top-end is ultra impressive, simply broader and stronger throughout – especially with that mammoth 14,000rpm limit! Finally, I feel KTM has made the most of its 250F motor since switching to fuel injection.

Whether you’re coming off a second or third gear turn, the motor pulls and responds to any bit of input you feed it through the throttle. Up hills, from a standstill or accelerating out of tight, slick sections, this motor ‘feels’ stronger and that’s important when it comes to excitement in the saddle.

The six-speed gearbox is smooth and precise, with no complaints here on my end. The hydraulic clutch is silky and one of my favourite things about the brand throughout all models. In fact, the operation of the 250F’s package seems refined and calculated, which explains its success in race series all around the planet.

Handling seems firmer and more precise than the 2011 model, but both are obviously good. The track at Louee was in freeway smooth conditions for much of the test, so we’re yet to see how it’ll fare as tracks roughen up (or in softer conditions). In saying that though, everything from initial turn-in, mid-corner feedback and acceleration is confidence-inspiring.

KTM launched its 2013 range at Louee in New South Wales. Image: Adam Riemann.

The 2013 KTM 250 SX-F was the favourite of many during the test, which is certainly saying something considering it was up against both the all-rounder 350 and brand new 450. I’m a 250F rider through and through, so for me, this newly improved model is a great thing.

I stepped straight up onto the 450 SX-F next, the bike that has so much hype about it and already an American title in its back pocket thanks to Dungey this year. Everything you knew about the last model, forget it, because the 2013 model is improved all round.

I’m the type of rider who doesn’t mind riding an Open bike and has owned a couple in the past, but if it’s not a friendly beast that I’m greeted by, my confidence is shot straight away. On this new KTM my confidence was high from the outset and even grew as I became more at one with the bike.

In places that the previous version would be hard to pull up under brakes or not quite willing to turn in where directed, this 2013 model responds to all input given at my speed. That was refreshing for me, a much more similar experience that I’d previously had with the 250 and 350 SX-Fs.

Ergonomically, like all models, it’s just right and promotes hard riding. It’s compact and no stone remains unturned it KTM’s search for comfort. On track, it’s a vital piece of the puzzle that allows you to ride exactly how you want to at the best of your ability.

The 450 SX-F is confidence inspiring and a major step forward. Image: Adam Spence.

KTM’s slogan ‘Ready to Race’ couldn’t be more true when it comes to 2013, although I did prefer the Renthal grips that were fitted stock on last year’s models (there are specific KTM branded grips on this year’s bikes). The handlebars have slightly more sweep and the seating position is spot on, suiting a wide variety of riders as well.

Like I said, the track wasn’t beat up at all, so I couldn’t yet say how it fares when the going gets tough in bumpy conditions. However, you only need to watch Dungey to see that this bike has all the potential in the world to be ultra competitive in race trim (remember the AMA enforces a production rule) no matter the track surface.

As I put in more laps I was able to charge harder, with only a little more risk as the bike responds so well. I could ride hard into turns and get on the gas hard when exiting. The Brembo front brakes work a treat, but the rear has a tendency to overheat as I drag it a little more on the 450. As for throttle response, it’s just so smooth (did somebody say EFI?) and invites you to twist the throttle harder with each lap until you reach the edges of your comfort zone.

Based off the EXC enduro model, I’d always been a big fan of that engine. It’s easy to see how it was transformed into a weapon on the motocross track too, because finally KTM has what we believe will be one of the most user-friendly motors on the market for 2013. Obviously a big benefit is the addition of fuel injection, which smoothens out the throttle response and brings it in line with the big four by scrapping the carburetor.

As David Pingree reported in his test of the US-only Factory Edition (very similar to the 2013 production model) for, the engine plays a big part in the 450 SX-F’s swift handling. It’s just easy to control, which essentially puts the ball in your court when it comes to how quick you’re willing to go.

Steering has been well refined across the board. Image: Adam Riemann.

All in all, KTM has made great inroads with its 450 SX-F and I’m sure that anybody who rides it will be well impressed. We’ve seen the factory team in the US do so well with this bike, but the real test will come when the masses start racing it worldwide over the coming months.

Last but not least was the 350 SX-F, the bike that I became so fond of when it was first released in 2011. It is the reigning world champion and has had so much success itself since being released, although factory teams in America and Australia that chose to race it last year have since scrapped those plans in 2012.

So what KTM has done is given it a power boost, elevating it closer in line with the 450s that it’s usually up against. It’s just what the 350 SX-F needed for the new year or it could have risked losing momentum, and the good thing is that KTM has retained its sensational handling that more closely mirrors a 250F than an Open class contender.

Cornering is where you’ll really make up time on the 350, but as mentioned above, you have to charge as though you’re on a Lites bike. As we’ve seen in racing, it’s somewhat easier to step up from a 250F than what it is to go backward from a 450 if you want to get the most out of the package.

To extract all you can out of the 350 engine you have to rev it like a 250F, because it just doesn’t have the torque of a 450. What you do need to work out is the gearbox if you really want to excel on this mid-capacity bike, because it is unique in the way it operates. Gearing will be critical if you’re a racer, but get it right and ride to its potential, you’ll reap the rewards with possibly less fatigue than on a 450 after a few hard motos.

Pulling up for turns is better than ever for 2013. Image: Adam Riemann.

It is a personal choice however, and since KTM now has one of the best 450s on the market with first class technology, the decision to buy the 350 is probably harder than it was a couple of years ago. To make the decision easier for consumers, KTM hosts its annual Dirt Days during September/October nationwide so you can test ride both (click here to check out our news story).

You’ll see that we’re super impressed on KTM’s advancements for 2013 and as usual, the Austrian manufacturer is pushing forward at a rate its rivals are rarely matching. With championships at the most elite levels of the sport worldwide, KTM is in a very strong position right now and its bikes certainly live up to the hype.

Technical Information

All Models
Not only visually does the completely revamped bodywork indicate that the 2013 model year represents a new SX generation. Above all, the ergonomics and function of the plastics have been designed in such a way that the whole chassis and engine package forms a perfect harmony with the rider down to the very last detail. The fuel tank and spoiler have been restyled along with the airbox cover and the front fender, including the start number plate. A particular highlight is the new front fender, which has no ribbing whatsoever on the inside, thereby preventing mud build-up. A pioneering structure and improved attachment of the fender to the triple clamp result in up to 50 percent greater lateral stiffness.

The modern frame design of lightweight, high strength, chrome-molybdenum steel section tubes guarantees an ideal mix of longitudinal and torsional stiffness, resulting not only in easy handling and precise steering behaviour, but also in excellent ride stability. The four-stroke frames impress in MY 2013 with a stiffening of the frame triangle and thinner-walled down tubes. This leads to an improvement in tracking stability (increased torsional stiffness) accompanied by a reduction in weight. The engine braces to the cylinder head have also been optimised, along with their attachment to the frame. The frame bears a new colour on all three models and it is still the benchmark in terms of weight and stability.

The further improved 48 mm upside-down fork featuring closed-cartridge technology has been optimised with completely revamped settings for perfect harmony with the new frame and engine. The new oil is significantly more wear-resistant and guarantees more consistent damping throughout both the course of a race and the bike’s life cycle. A new lower triple clamp is 80 grams lighter and, just like the upper triple clamp, CNC-machined from high quality aluminium, whereby the steering characteristics and hence the responsiveness of the fork have been noticeably improved. All fork settings are specific to the bike’s class.

KTM has a slick SX-F range for 2013. Image: Adam Riemann.

Shock Absorber
The WP monoshock has been further refined for 2013 and, together with the KTM linkage system, it excels with its completely revamped settings for improved damping, more traction and even higher reserves against bottoming out. As ever, rebound and compression damping (high and low speed) can be adapted individually to the track and rider in no time at all. Like the fork, settings are model specific.

The cast aluminium swingarm has been developed with state-of-the-art calculation and simulation software and constructed, in terms of design and wall thickness, for minimum weight with optimum stiffness and sufficient flex. For the 2013 model year, engineers have redesigned the rear section of the swingarm to allow installation of a thicker rear wheel axle (25mm instead of 20mm) for the benefit of better tracking stability. Moreover, they have succeeded in reducing weight by more than 100 grams by revising the bolts, cups and nuts on the linkage.

The wheels are fitted with lightweight, CNC-machined hubs and high-end EXCEL rims, plus new, black-coated spokes with aluminium nipples, guaranteeing the highest levels of stability while keeping weight to a minimum.

Brakes from Brembo are standard equipment on KTM motocross bikes and, together with lightweight wave brake discs, they are recognised as the measure of all things in terms of application and brake performance. At the rear wheel, the brake calliper carriers have been adapted to the larger axle diameter for MY 2013.

New Injection System
The Keihin engine management system with electronic fuel injection has been improved significantly. Even more performance has been achieved with greater air flow through a new throttle body, featuring a 44mm instead of a 42mm port in conjunction with the new injector nozzle. The throttle position sensor (TPS) is harder wearing and protected from stone impact with a plastic protector. The connectors are now enclosed in rubber grommets to protect them from steam-jet pressure. The wiring harness has been simplified and the quality of cables and connectors optimised. Additional engine characteristics can also still be activated with an optional map-select switch on the handlebars.

Electric Starter
Every millisecond counts when starting and all three models can be started simply at the press of a button. This is an invaluable benefit in the heat of a motocross battle.

The 450 SX-F has proven a winner with Ryan Dungey in the US. Image: Adam Riemann.

2013 KTM 450 SX-F (specifics)
Less weight, less maintenance. But, because you can’t save on everything, the 449.3cc SOHC SX-F engine offers one major plus: more power. If you combine the two kilograms saved by the more compact design with the unbelievable 60hp, you end up with unparalleled power development and handling previously unheard of in the MX1 class. It’s based on the proven 450 EXC engine.

Cylinder Head
This is precision engineering: a cylinder head reconfigured for optimal motocross characteristics with a very broad rev range. In this extremely compact and lightweight construction, only one camshaft specially designed for the KTM SX-F actuates four titanium valves via weight-reduced rocker arms (DLC-coated on the intake side). Together with ultra-light valve springs and spring retainers, a maximum engine speed of up to 11,500rpm can be achieved for maximum power.

The crankshaft on the new KTM 450 SX F with a 63.4mm stroke is equipped for 2013 with a revolutionary plain bearing in the lower conrod eye. This means that the conventional needle bearing is replaced by two press-fit bearing shells in the ultra-light Pankl connecting rod, which run directly on the crankshaft’s additionally reinforced crank pin. The sliding bearing is supplied with oil directly from the pressurised oil circuit via the crankshaft. The need for servicing the crankshaft is halved. And, because the gyrating mass has been reduced, the bike has more bite and it’s even more agile and dynamic.

A new DDS clutch (Damped Diaphragm Steel) with a wear-free steel cage is fitted to the new KTM SX-F engine, allowing use of thin steel discs for minimum overall width. The diaphragm spring, which preloads the package, not only reduces the operating force required to pull the clutch, but also provides space for integrated hub damping. The result is that it has more traction and protection for the transmission. And with hydraulic clutch actuation from Brembo, the rider has everything under control right from the start.

2013 KTM 350 SX-F (specifics)
Revamped Engine
The advantage of the KTM 350 SX F has always been its weight. And now the bike’s heart is even lighter. Another 500 grams and more have been lost thanks to the new die-cast housing. The extremely short-stroked DOHC power unit, equipped with the latest generation of EFI, excels with its even wider rev range and exceedingly efficient rideability. And, just like all KTM four-strokes, it can be activated with an electric starter.

Your current world champion, the KTM 350 SX-F. Image: Adam Riemann.

Cylinder Head
The modifications to the 350cc DOHC engine can be summarised very easily: more power at less weight. Flow-optimised ducts supply greater gas flow and therefore better cylinder charging. Strengthened valve heads and valve seats plus valve springs with a higher spring force make it possible for the lightweight titanium valves to withstand the increase in maximum engine speed from 13,000rpm to 13,400rpm.

Factory bike or production bike? You’ll find no difference in the crankshaft. Just like last season’s KTM factory machines, the crankshaft on the new KTM 350 SX F 2013 is equipped with a revolutionary plain bearing in the lower conrod eye. In conjunction with the stiffened crankshaft and a lighter piston, this design is a key prerequisite for increasing the maximum engine speed to 13,400rpm and the impressive peak performance of the 350cc engine. But not everything revolves around pure power. One major benefit is an extension to the service intervals for the crankshaft, a benefit in terms of time and costs.

2013 KTM 250 SX-F (specifics)
A completely new design, without kickstarter, in a new engine case, manufactured in a die-casting process. It’s now based off the 350 SX-F engine. What’s all this for? To save weight. A new, elastic and simultaneously high-strength, aluminium alloy provides additional damage protection for the engine on the KTM 250 SX F 2013.

Cylinder and Piston
The stroke-bore ratio of the KTM 250 SX F 2013 has been defined as somewhat shorter-stroked for the benefit of higher peak power, with the new cylinder now boasting a bore of 78mm (previously 76mm), hence providing space for larger valves. Despite the larger diameter, the box-type, forged piston is lighter in weight. This reduces the moving masses and enables higher engine speeds as well as more power.

Balancer Shaft
The goal was less vibration in spite of increased revs. That’s why the new KTM 250 SX-F engine also has a laterally positioned balancer shaft, which also serves as the drive wheel for the timing chain and the water pump.

Cylinder Head
Those wanting to know what drives a winner to victory will find the answer here. The heart of the newly developed DOHC engine is the redesigned cylinder head with twin overhead camshafts and DLC-coated cam followers that actuate the titanium valves. Larger, flow-optimised ducts in conjunction with the more generously dimensioned intake valves (intake 32.5mm, exhaust 26.5 mm) guarantee 10 percent more gas flow and therefore significantly improved performance. The new camshafts on the 250 SX F 2013 have also been designed (new valve timing, larger stroke) for achieving a huge increase in performance compared with the predecessor model, above all at the top end of the rev range at 14,000rpm (previously 13,400rpm).

The 2013 KTM 250 SX-F has made great steps forward. Image: Adam Riemann.