MOTOCROSS ACTION’S 2011 KTM 350SXF VERSUS KTM 450SXF SHOOTOUT:

January 2, 2012
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There is a point in every motocross racer’s life when he believes in magic. No, not voodoo, psychic readings or David Copperfield. Motocrossers cling to the idea of the “magic motorcycle”?the machine that will change them from an also-ran into a front-runner; the bike that will make all their dreams come true; the single motorcycle that will change their lives. For obvious reasons, the idea of a “magic motorcycle” is ludicrous, but there are plenty of stories about riders who got off a KX450F and onto a YZ450F and found bliss. Of course, for every KX450F-to-YZ450F cosmic moment, there is a YZ450F-to-KX450F counterpart.

The MXA wrecking crew discounts the “magic motorcycle” concept because we ride, race and test every motorcycle made (on a weekly basis), often switching back and forth from one brand to another between motos. If there is magic to be found, it has more to do with good engineering than pixie dust. But, technical superiority aside, there are lots of differences between the bikes built by Honda, Husqvarna, Yamaha, KTM, Suzuki and Kawasaki. A lot of know-nothings like to say, “All the modern bikes are the same?you only have to choose the color you like.” Nothing could be further from the truth. None of the bikes are alike; none handle the same; every powerband is unique; and not every body shape works in harmony with the setup of a given brand.

Finding the perfect bike, maybe even the magic bike, doesn’t come from the color of the plastic or the number of race wins tallied by high-paid superstars. Nope, it comes from a cold, hard, analytical evaluation of each bike…and then matching that to the rider’s unique needs.

THE MXA WRECKING CREW’S SEARCH FOR THE MAGIC BIKE

Which brings the MXA wrecking crew to the 2011 KTM 350SXF. Touted by pundits as the perfect machine, MXA decided to put it up against its most worthy contender?the 2011 KTM 450SXF. This isn’t an apples and oranges shootout. The two orange machines come from the same factory, use the same suspension components, share a design philosophy, are developed by the same factory test riders, get their technology from the same engineers and, most importantly, are regulated into the same class. Not a single MXA test rider could use bar bend, lever shape or seat height as an alibi, because these two bikes are as close to identical as possible.

This isn’t a poor man/rich man shootout. Both the KTM 450SXF and KTM 350SXF offer status and performance in comparable packages. They are the hottest Open-class motocross bikes on the market. Both have been freshly minted with new frames, plastics, shock linkages and swingarms. This isn’t old iron versus new iron?this is a comparison between two high-tech bikes that want to own the Open class. They may come at it from difference angles, but never have two bikes been more primed to line up against each other in a shootout.

SECOND PLACE: THE 2011 KTM 350SXF

2011 KTM 350SXF: The 350SXF isn’t a light 450 as much as a powerful 250. It has to be revved to 12,200 rpm to get full use out of its two-stage powerband.

Yeah, yeah, yeah. We know that you are shocked that the KTM 350SXF didn’t win this shootout. That it received a thorough thrashing at the hands of the KTM 450SXF may seem like breaking news to you, but the MXA wrecking crew had an inkling of the 350SXF’s weakness the first time we threw a leg over it. We admit that if hyperbole, public opinion and posturing could be harnessed, then the 350SXF would have been the odds-on favorite to take the top spot in this shootout. After all, it’s the first of its breed. The idea of putting a midsized, 350cc, four-valve engine into a light and lively chassis had everyone drooling over the potential of a race bike with the perfect amount of power blended with 250-style handling. Plus, there was a lot of rabble-rousing clamor from the unwashed masses about 450cc motocross bikes being “too powerful.” The idea of a midsized, Open-class four-stroke seemed to be an unassailable slam-dunk to the casual motocross fan. We admit that the ingredients packed into the 350SXF package presage a serious racing experience, but all the soothsayers were wrong.

Oh, don’t get us wrong. The 2011 KTM 350SXF is a fine machine. It offers a style of power that bridges the gap between a 250cc four-stroke and a 450cc behemoth. The 350SXF has some advantages over the 2011 KTM 450SXF. Here they are:


   
KTM 350SXF versus KTM 450 power: The 350 engine is a revver. It doesn’t make it peak horsepower until 12,200 rpm. That is screamin’ territory. The 450SXF engines makes it peak horsepower at a much lower 8000 rpm.


Weight:
When we first hoisted the 350SXF up onto MXA ‘s scale, we were so dumbfounded that we took it off the scale to check the mechanism. Then, we put it back up a second time…and a third time, and a fourth time. By the time we were done with this weightlifting exercise, we wrote the weight down as 237 pounds. Say it isn’t so! It was a lot heavier than we were led to believe it would be…and heavier than we hoped for.

Next, the 450SXF was dead lifted into place?242 pounds. The end result was that the 350SXF weighs a meager five pounds less than the 450SXF. We can give you a million reasons why the tonnage difference isn’t greater, but suffice it to say that true to the hype, the 350 weighs less than the 450SXF. ‘Nuff said.


In motion the 350SXF feels lighter than it small five pound weight difference over the 450SXF could account for. Most of the light sensation is the result of rotating mass in the engine and higher rpm.

Weight in motion:
Okay, the five-pound weight difference was a bummer. We expected the 350SXF to be 15 pounds lighter than the 450SXF. It wasn’t. But on the racetrack, it feels 15 pounds lighter. How can a moving object weigh less than a stationary object? Assuming the same G-force, it can’t, but there are other forces at work on a moving machine. Bikes with less horsepower and torque tend to feel lighter because they aren’t as solidly hooked up to terra firma. Bikes with smaller pistons, valves and cams exert less angular force on the chassis because their rotating mass is less. So, the KTM 350SXF feels much lighter because its weight is less detrimental in motion.


From a mechanical point of view, with the exception of the engine, spring rates and frame down tubes, the 350SXF is the 450SXF.

Handling: The geometry, dimensions and frame specs of the 350SXF and 450SXF are locked in a virtual tie. If you are looking for a difference, don’t look at the wheels, tires, suspension components, gas tank, airbox, saddle, triple clamps or plastic. Nope, instead look at the down tubes that swoop under the engine?that’s the only difference. The larger 450SXF has less kink to the tubes.

The reality of the handling differences doesn’t come from the owner’s manual specifications, but instead from the common sense factor that a bike with less power, more rev and decreased rotating mass will be more agile than the identical bike with more torque, more thrust, more power and more gyroscopic effect from the drivetrain.

Most MXA test riders felt that the 350SXF could dust the 450SXF through tight corners, ruts and rough sweepers. In the difficult corners, the lesser throttle response of the 350 powerplant didn’t inject any negative gyroscopic precession into its chassis. As we accordioned from one corner to the next, the 350 transferred from a light feel to moderately heavy, while the 450 was always more hooked up and weighted in transitions from left to right. The 450SXF didn’t resist roll transitions, but it didn’t have the snappy roll rate of the lighter 350SXF. Over jumps, the pitch changes were easier to control on the zingy 350 engine compared to the 450SXF’s tendency to take bigger swings in its up/down angle based on throttle input. Fixing a nose-down situation was quicker on the 350. In essence, the lighter-feeling 350SXF was far easier to manage.


The airbox on both the 350 and 450 require no tools to get to.

Engine technology: Both the 350 and 450 engines employ cutting-edge technology, but from a scientific point of view, the KTM 350SXF has a clear advantage with its Keihin fuel injection, compact engine, electric or kickstart options, and up-to-the-minute design (the 450 engine is four years older).

Price: The 350SXF costs less than the 450SXF, but we don’t know why. They share virtually every component, and we must assume that the 450 engine is cheaper to build based on its simpler electronics, carburetor and the fact that its mold costs have been amortized over a longer period of time. That said, the KTM 350SXF retails for $8499, while the 450SXF price tag is $8799.

FIRST PLACE: THE 2011 KTM 450SXF

2011 KTM 450SXF: It’s not not to appreciate the charms of a massively powerful engine that shifts perfect, starts with the push of a button and is as easy for a Novice to use as a Pro.
 
Yeah, yeah, yeah. We know that you are shocked that the KTM 450SXF won this shootout. But, you aren’t so stupid as to believe that when two machines are as close to identical twins as possible, the one with 11 more horsepower at 7000 rpm isn’t going to win. Even if we subtracted points for its five extra pounds, lack of fuel injection and heavier feel, it is still a better race bike than the 350SXF.

Test results don’t lie; the 450SXF pulls harder than the 350SXF at virtually every rpm range. In fact, a 450SXF devours the 350 easily, rarely needs to be shifted, and doesn’t have to be revved to 12,200 rpm to make its best power. The KTM 450SXF is a bike that MXA test riders refer to as “seamless.” It has virtually no faults; nothing falls through the cracks. It is fast, torquey, easy to ride, sharp handling and decently suspended. Its incredibly broad and flexible powerband puts an end to the misconception that 450cc motocross bikes are “too powerful.”


It comes with electric start (and the requisite battery), but weighs less than the Yamaha YZ450F, Kawasaki KX450F or Suzuki RM-Z450.

When you add the benefits of the new chassis, plastic and ergonomics to the lusciousness of the KTM 450SXF engine, you get a machine that requires no trepidation to use it to its fullest. It can be ridden slow. It can be ridden fast. But best of all, it has lots of power options to suit any situation it faces. See the berm? Nail the throttle. See the flat sweeper? Roll the throttle on. See the long straight? Put it in hyperdrive.

When you compare the KTM 450SXF to the 350SXF, you have to weigh the good and the bad. The 450SXF is heavier, and because of its horsepower, it feels heavier. But, the 450SXF has some advantages over the 2011 KTM 350SXF. Here they are:

Horsepower:
You can’t help but be impressed with this powerband. The 450SXF engine is so good that almost anyone would be faster on it than on whatever he is riding now. And, if you are on a 350SXF, you learn quickly that the 450SXF guy in front of you isn’t trying half as hard to go the same speed.

Why doesn’t he have to try? Because at 6000 rpm, the KTM 450SXF is making 35 horsepower, while the 350SXF is down around 24 horsepower. At 8000 rpm, the 450SXF produces close to 54 horsepower; at the same rpm, the 350SXF is around 42 ponies. The story at 10,000 rpm is the same, but the revvy 350 closes the gap a little (51 horsepower to 45 horsepower). It isn’t until 11,500 rpm that the 350SXF catches the 450SXF on the dyno chart (but the 450 peaked 2000 rpm before that).

The 350SXF isn’t tuned the way MXA would like it. It is basically a slow 450 until 9000, and a powerful 250 from 9000 to 12,200. We expected a broad, midsized, torquey powerband from the 350SXF?something closer to the Yamaha YZ400 powerband?not a hot rod rev ranger that requires a full-out commitment on every square inch of the track.  We’d want one well-defined 350cc powerband instead of two totally different powerbands. KTM should bring the powerband down and blend more low–to-mid with a solid midrange.


KTM has the best brakes on the track. They have no competition when it comes to pucker power.

Suspension: If you accept our logic, then there is no contest between the suspension on the 350SXF and the 450SXF. Both bikes are built and designed to race in the 450 class. The weight difference between the two machines is negligible (not counting gyroscopic effect). So why does the 350SXF come with suspension components that are too soft? After struggling with the 350SXF forks and shock, the MXA wrecking crew put the stiffer 450SXF components on the 350 and lived semi-happily ever after. We dropped the stock 0.46 fork springs (which are way too soft) for the 0.50 springs from the 450SXF and juggled the oil height to suit track conditions. In the rear, our solution was to swap out the stock 5.4 shock spring for the 5.7 spring from the 2011 KTM 450SXF. This held the rear up higher and allowed us to balance out the chassis in coordination with the stiffer fork springs.

Carb versus fuel injection: From a technical standpoint, we accept that the 350SXF’s fuel injection is more modern than the old fashioned Keihin FCR carburetor on the 450SXF, but one ride on the 450SXF will dispel the idea that EFI is better. The 2011 KTM 450SXF has a sweet, well-modulated low end and a romping, stomping top end. Everyone brags about the crisp low-end throttle response of EFI, but them reprograms the ignition to get rid of it?that makes it more like a carbureted bike.

Gearing: The original KTM 450SXF had a four-speed gearbox. The four-bangers required the rider to make compromises; he had to choose thrust or speed (and gear the bike up or down to achieve it). When the five-speed was introduced in 2010, it was like a breath of fresh air. The five gears are adequately spaced to make the most of the long powerband, and the option of going lower for more thrust is a simple task.

The 350SXF gearbox is not well mated to the midsized powerband. We typically geared it down one tooth (from 50 to 51), while several MXA test riders chose to gear it down two teeth. In our opinion, the gap between gears is too large to work with the 350SXF’s high-rpm powerband. With the stock setup, the 350 has a hard time making the jump from second to third, and it takes a long straight to get the rpm up to the rev limiter.

WHAT DO WE REALLY THINK?

For all the hip, cool and youthful excitement that the KTM 350SXF generated, we didn’t find true racing nirvana on it. We have no doubt that this would be a great bike for a play rider or a racer trying to make the move from the 250 class to the 450 class. If KTM moved the 350SXF powerband down into the typical 450 range and stiffened up the suspension a bit, it would be a better race bike.

As it stands, the 2011 KTM 450SXF is the hands-down winner. The 450SXF is fully optimized for racing; the 350SXF is not.

For the complete KTM 350SXF test click here

For the complete KTM 450SXF test click here


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