The release of the all new KTM 350SX-F has sparked worldwide interest and is the latest open class racer from the KTM factory. Inspired by MX legend Stefan Everts, the 350cc four-stroke is aimed at taking control of the 450cc MX class and is KTM’s flagship model in the big-bore category.
An all new creation from the ground up, the 350 has got all the bells and whistles, and is arguably one of the most creative and innovative production bikes in recent history, and it's already got runs on the board by winning a world championship.

A 350cc thumper up against a pack of 450s is no easy task, and it’s a very ballsy move by KTM to campaign a smaller capacity bike up against the biggest and fastest motocross bikes on the planet. The jury is out on this machine, and as the new race season begins we will soon find out if 350cc is capable of putting it to 450cc away from the factory-backed GP scene. Cast your mind back a few months and you will remember we were impressed when Cycle Torque got to ride the 2011 KTM range earlier in 2010 at the KTM MX range launch: so much so we decided it would be a great idea to give it a more thorough test on familiar turf at our own MX test track in the NSW Hunter Valley.

Engine
The engine is obviously the big ticket item here, it is a computer designed, purpose built 350cc, four-valve DOHC, water-cooled, four-stroke powerplant. It’s not a big bore 250F and it’s not a sleeved down 450F. It’s a straight up brand new concept 350cc design. Look beyond the naked eye and you will find a host of top notch engine features on the new KTM: there is a motocross-specific five-speed gearbox, Keihin Electronic Fuel Injection, Magura Hydraulic clutch and possibly the most convenient new feature – electric start. As soon as you take off down the track you immediately notice that the 350cc motor is full of life and has plenty of power under the hood.

After making a few personal adjustment to the cockpit we began to settle into a rhythm on the 350 and throw down some competitive laps. The motor is certainly the most impressive part of the 350SX-F, it is very easy to adapt to and is very confidence inspiring. It’s free-revving and wants to be ridden hard like a small bore 250F yet much more powerful and punchy. It’s got good power off the bottom and is at its strongest through the mid and top end. Chassis & Suspension An all new chassis was developed for the KTM SX-F range in 2011.

Sticking to their beliefs and what works for the orange bikes, the KTM engineers tweaked their Chromoly Steel cradle, added extra torsional rigidity and a new shock mounting system. The top of the shock now mounts to what some might consider to be a sub-frame which is welded towards the rear of the chassis.

This is aimed at taking the rear shock forces away from the rest of the chassis and to isolate the shock forces to the mounting frame built onto the rear of current chassis. The KTM four-strokes now come with a linkage system, something consumers have been crying out for. 2011 will be the first time the Austrian brand will incorporate a linkage in their production line, since... well a very long time ago.

Once again for 2011 KTM have enlisted the services of WP suspension to handle all of their suspension components, the range is similar to what can be found on any 2010 SX-F model, however with obvious modifications to suit the new chassis and linkage.
After settling into a good pace around the motocross track and getting used to the KTM it was time to give the suspension a workout and see what this 350 was all about. For standard equipment the 350 suspension works well in most across the board situations.

We made some clicker adjustments during the day to get the most out of the WP suspension, we found the standard setting to be a little bit busy and we worked on calming down the feel of the suspension to make things a bit more comfortable on the rider, which we achieved.
The 450 While the 350 is the talk of the paddock and is taking all the glitz and glamour, the 450 received its fair share of updates and hasn’t gone completely unnoticed by the Austrian factory.

We thought it would only be fair to bring out the big guns and ride the 450 on the same day as the 350, this would give us a more accurate comparison of how each bike stacks up in the big bore class and how competitive these two bikes are. Once again KTM came up with the goods and bought along a 2011 450SX-F for us to have a play on.

What’s new
The big-bore KTM got an all new chassis along with the rest of the fleet, and also got the new SX-F linkage system.
A new swingarm compliments the new shock/linkage/chassis system and also sheds around 300g when compared to the previous model. Also on list is a new wheels front and rear. The KTM factory have gone back to silver Excel rims, instead of the black they have been using in production for a while now, and also have a new coating on the spokes and spoke nipples. Last but not least the 450 shares the all new bodywork on the 2011 KTM SX-F models, all new plastics and graphics make for an updated, modern new look.

On the track:

Roll onto the track and the 450 certainly feels different to the 350. The bike feels a bit bigger, and the motor gives you much more of that “big bore” feel as it tends to chug off the bottom. The power on the KTM 450SX-F is plentiful as you roll on juice, the motor is very strong has plenty of grunt. It not a fast paced, “rev me silly” type of power, it's strong and torquey and gets up to speed very fast without too much effort.

The KTM 450SX-F is equipped with a Keihin Carburettor and is jetted well right off the showroom floor, while we have no problems with the trusty old carby on the 450 as it does everything we ask and more, it would be nice to see KTM look at EFI on their big bore thumper. Verdict: Well after a long day at the office testing the KTM 350SX-F and 450SX-F we were all feeling pretty tired. The test was not so much to find a “winner” out of these two bikes, more so to see how they both fit into today’s open class motocross market.

On tracks where horsepower rules than it would be hard to look past the power and punch of the 450. It was so much fun trying to use all the power underneath the bonnet of the big KTM.
Add some tight lines and big bumps and soon enough the smaller 350 comes into play as it feels that bit lighter and easier to ride as the laps continue and all your energy get left behind. It would be a hard decision to choose between the two, and there are many things to consider if you are in the market for either of these bikes, but you can't really make a bad decision – both bikes are good machines.