MXA’S 2012 KTM 450SXF MOTOCROSS TEST: THE BIKE THAT BLOWS HOLES IN THE FUEL-INJECTED THEORY

December 11, 2011
Comments off
881 Views
facebooktwittergoogle_plusredditmailfacebooktwittergoogle_plusredditmail

Q: FIRST AND FOREMOST, IS THE 2012 KTM 450SXF FUEL INJECTED?

A: Nope, and unlike the mob majority of a world sold on technology, the MXA wrecking crew is glad. Why? History has proven that fuel injection, for all its hype, does not make an engine better in the first year of its development. Think about how awesome the 2008 Honda CRF450 engine was and how one-dimensional the fuel-injected 2009 CRF450 was. The same scenario has replayed itself with a host of bikes that go from awesome to mediocre with the advent of EFI. Given our druthers, we’ll keep the big, broad and bold power that a carb produces until all the experimenting is done (on someone else’s dime).

When KTM deems fuel injection necessary (which wil be soon), let’s hope they have better luck than the majority of their competitors did in year one of EFI. Virtually every previously carbureted bike lost horsepower and went flat on top after switching to fuel injection. Each brand, save for Kawasaki, struggled for two or more years before getting back what they lost. We’d prefer not to waste a year or two trying to get back to where the KTM already is.

Q: HOW DOES THE 2012 KTM 450SXF ENGINE DIFFER FROM THE 2011 450SXF?

A: In one way and one way only. The 2012 KTM 450SXF engine gets the most creative clutch ever put on a production bike (we’ll get to it later).

Q: IS THE 2012 450SXF FASTER THAN THE 2011 450SXF?

A: No. Why not? Because it is the same engine in every detail?save for the clutch.

2012 KTM 450SXF: When you have won the 450 Shootout in 2010 and 2011 there is no pressing need to alter your 2012 race bike. KTM stood pat for 2012, but added the most ingenius clutch ever designed to the package. 

Q: HOW GOOD IS THE 2012 KTM 450SXF’S POWERBAND?

A: This is Everyman’s powerband. It has such a broad and useable output that there is something for everyone from rank Beginners to ranked AMA Pros. It is hard to imagine a powerband that is so easy to use at low rpm (from 5000 rpm to 7000 rpm), but still rips from 7500 all the way to its 11,600 rpm sign-off. It is the breadth, from bottom to top, that makes the 450SXF so easy to ride. While its peak horsepower is a respectable 53.24 horsepower at 8800 rpm, the KTM 450SXF is still making 49 horsepower at 11 grand. And even when the rev limiter kicks in at 11,600 rpm, it is pumping out 45 horsepower. That is all useable power?to the very last drop.

The 2012 KTM 450SXF doesn’t make the most horsepower in the class (the 2012 KX450F peaks out at 55.50 at 8900 rpm), but it has the broadest, easiest-to-use and most organic power on the track. You just roll it on and it goes. It doesn’t lurch into action at low rpm. It doesn’t go flat on top. It doesn’t hang at peak. It just keeps going. If you want to go faster, all you have to do is keep the throttle pegged.

Q: WHAT DON’T WE LIKE ABOUT THE 2012 KTM 450SXF POWERBAND?
 
A: Now that we’ve told you how much we love the KTM 450SXF’s powerband, we need to tell you what we don’t like about it. First, the faster the MXA test rider, the more he wanted a harder and more abrupt hit. The Vets and Novices loved the easy roll-on power, but the Pros wanted it to go now, or sooner.

Our solution was to gear the 450SXF down (from a 52-tooth rear sprocket to a 53). This punched up the low-end and made things happen quicker?and allowed us to get to third sooner. In the end, the Vet and Intermediate test riders preferred this gearing also. The gearing could go even lower for a Pro if he traded the countershaft and rear sprockets for a 13/50. The stock 14/52 has a 3.714 ratio; our preferred 14/53 generates a 3.786 ratio, and 13/50 yields a 3.846 ratio (the equivalent of a 14/54).


Personality: There is no other 450cc engine that can be as gentle at low rpm and powerful at high rpm as the KTM 450SXF. It has an amazingly versatile powerband.

Q: WOULD THE 2012 KTM 450SXF RUN BETTER IF IT WERE FUEL INJECTED?

A: Maybe, and maybe not. As a rule, fuel-injected 450s tend to run crisper down low and flatter on top. This is the opposite of the 450SXF’s personality.

On the news front, KTM has a new, fuel-injected, die-cast, 450cc engine in its 2012 450EXC enduro bike (and this is the engine that Ryan Dungey is using and KTM will switch to when the mid-season 2012-1/2 450SXF is released in a few months). As for us, we are glad that KTM has stuck with the trusty 41mm Keihin FCR.

Q: HOW IS THE JETTING?
 
A: We didn’t have to change any jets on the 2012 KTM 450SXF. MXA‘s recommended jetting is as follows:
    Mainjet: 185
    Pilot: 42
    Needle: OBDTQ
    Clip position: 6th from top
    Fuel screw: 1-3/4 turns
    Leak jet: 50
    Notes: The leak jet and fuel screw adjustments were the only jetting changes we had to make. If the bike doesn’t light up immediately with the electric starter, richen the fuel screw.

The KTM 450SXF is the only motocross bike to come stock with a Belleville washer-activated clutch…and that is only one of its unique features.

Q: WHAT’S WITH THE WEIRD CLUTCH?

A: It’s not weird; it is creative?the most creative clutch ever put in a production bike. How so?

(1) Steel basket. The steel basket is smaller and stronger than the previous unit, which was a copy of the 2008 CRF450 clutch. It will never wear out or get notches in the tangs.

(2) Primary gear. The primary gear is CNC-machined directly into the clutch basket. This eliminates the need to rivet a separate gear to the back of the basket?in addition to making the clutch pack narrower.

(3) Rubber dampers.
KTM has installed rubber dampers inside the inner hub to cushion the shock of the drivetrain.

(4) Belleville washer. Instead of six separate coil springs to provide tension, the 2012 KTM clutch uses one large cupped washer (KTM calls it a diaphragm spring) to provide the tension.

(5) Spring preload. Unlike coil-spring clutches, the Belleville washer can be preloaded for more or less tension by turning a stepped disc.

(6) Driven plates. The driven plates are steel instead of aluminum, which lessens wear on the plates and reduces oil contamination. Take note that the outermost and innermost steel plates are thinner than the rest of the clutch plates.

(7) Hydraulics. The whole system is hydraulic, which means that it self-adjusts and lasts twice as long as a cable clutch.

(8) Feel. Every MXA test rider felt that the new clutch had a more precise and positive feel than the old coil-spring clutch. We set the adjustable preload on the stiffest setting.

Q: HOW MUCH DOES THE 2012 KTM 450SXF WEIGH?

A: 243 pounds (without gas). Just for comparison, the 2012 Kawasaki KX450F weighs 242 pounds on the MXA scale, but doesn’t have electric starting. The Honda CRF450 weighs 231, YZ450F 238 and RM-Z450 244.


Locked up: KTM’s nylon preload ring is pretty when new, but after a few uses it starts to look like hammered dog meat.
 
Q: HOW DOES THE KTM SHOCK LINKAGE WORK?

A: KTM’s engineers had the benefit of being late to the rising-rate linkage party. They didn’t have to experiment with damping curves, link arms or overall design. Instead, they studied the available systems and copied, to some degree, the rising-rate linkage of a Yamaha YZ450F. Good move, because of all the current rear suspension systems, Yamaha’s is at the top of the heap.

The pluses of KTM going to a proven, albeit borrowed, rising-rate system are that more shock stroke is available, rate changes can be configured quicker, adjustment is achieved with less hassle and public opinion insists on it.

Do we think that KTM’s rising-rate setup is better than their no-link PDS system of the past? Yes. As it sits on the showroom floor, the linkage system is set up better. Do we think that the linkage system is better than the PDS system on principle? That ship has sailed, but the honest answer is that a properly setup PDS system would work equally well?and weigh 5 pounds less.
 
Q: WHAT WAS OUR BEST SHOCK SETTING?

 
A: For hardcore racing, we recommend this shock setup for the 2012 KTM 450SXF:
   Spring rate:
5.7 kg/mm stock
   Race sag:
100mm
   Hi-compression:
1-1/4 turns out
   Lo-compression:
12 clicks out
   Rebound:
12 clicks out
   Notes:
For riders in the 200-pound range, we recommend going to a stiffer 6.0 kg/mm shock spring. We also use an X-Trig worm-drive preload adjuster to avoid KTM’s faulty nylon preload ring.

Q: WHAT WAS OUR BEST FORK SETTING?
 

A: For hardcore racing, we recommend this fork setup on the 2012 KTM 450SXF:
   Spring rate:
0.50 kg/mm
   Oil height:
375cc
   Compression:
12 clicks out
   Rebound:
12 clicks out
   Fork-leg height:
5mm up
   Notes:
If you think the forks dive too much, which most MXA test riders do, you can raise the fork-oil height by 10cc. Unless you are a bantamweight, we don’t think the WP forks will be too stiff for you. KTM increased the compression damping slightly over 2011, but they could go firmer. The quickest way to firm up the middle of the stroke is with an aftermarket spring seat kit.


Head start: The 2012 KTM 450SXF is the only KTM?(or any other brand) to come stock with a holeshot device.

Q: HOW DOES THE 2012 KTM 450SXF HANDLE?

A: Once you get the fore/aft balance right, this bike handles like a dream. The 63.5-degree head angle tracks accurately through corners and goes down straights like it’s on rails.

Is it better than a Suzuki, Kawasaki, Honda or Yamaha? Yes. It is significantly better than the Honda, Yamaha or Kawasaki, but only better than the Suzuki in that it’s more versatile; the RM-Z450 is tuned to corner like a banshee?and little else.

Q: WHAT IS THE SUGGESTED RETAIL PRICE OF THE 2012 KTM 450SXF?

A: The 450SXF sells for $8799.

Q: WHAT DID MXA DO TO MAKE THE 2012 KTM 450SXF WORK BETTER?

A: Here is the list:

(1) Gearing. Most MXA test riders preferred to run a 53-tooth rear sprocket to get more drive in second and to get to third gear sooner.

(2) Fork setup.
These are very good Vet forks. If you are faster than the typical Vet or smaller than the target 175-pound rider, you will need to fiddle with the oil height; 10cc more for fast guys to eliminate bottoming, and 10cc lower for small guys to make bottoming possible.

(3) Gas cap. We cut off the tangs on the gas cap to disable the locking device. (If you do it just right, the gas cap will click off, but it won’t take two hands to open it.)

(4) Exhaust system. The 450SXF’s power delivery can be modified with aftermarket pipes. The Pro Circuit pipe added a lot more top-end power, while the DR.D and FMF pipes beefed up the low-to-mid power.

(5) Iron phosphate battery. We removed the stock 3-1/2-pound Yuasa lead-acid battery and replaced it with a 1-pound aftermarket battery.

(6) Tires. We think that the old-school Bridgestone M59/M70 tires were better than the Dunlop MX51 combo on the 2012 model?and we know for sure that they were lighter. Given our druthers, we’d drop-kick the front MX51 for an MX31 or a Bridgestone 403.

(7) Clutch preload. We turned the clutch preload dial to one hash mark to put the most pressure on the Belleville washer. This made the clutch action better. It is also possible to change the spring preload by replacing the outermost and innermost steel clutch plates with thicker clutch plates from the middle of the pack.


Great Houdini: When it comes to handling, KTM has the patent on designing bikes that carve through turns like they have ground effects.

Q: WHAT DID WE HATE?

 A: The hate list:

(1) Handlebar bend. They are too low. We installed KTM Power Parts risers to raise them 5mm, but most test riders preferred 12mm taller Renthal 603 (Windham) FatBars or 19mm taller Renthal 604 FatBars.

(2) Shock preload ring.
This is the worst preload ring in history; although it wins brownie points for being accessible?unlike the preload rings on the Japanese brands.

(3) Weight. According to studies, 60 percent of Americans are obese. That may sound terrible, but 80 percent of the Big Five’s 450 motocross bikes are obese. The Yamaha YZ450F (238 pounds), Suzuki RM-Z450 (244 pounds), Kawasaki KX450F (242 pounds) and KTM 450SXF (243 pounds) could all stand to take diet advice from Honda (231 pounds). Oink!

 
Shhhh: The 2012 KTM?450SXF meets both the AMA and FIM sound standards. Most 2012 bikes can’t pass both tests.


Q: WHAT DID WE LIKE?

 A: The like list:

(1) Rear brake seals . On past Brembo rear brakes, the seals inside the rear master cylinder could get nicked at extremes of pedal travel. For 2012, Brembo repositioned the brake bleed hole so that it doesn’t touch either seal.

(2) White plastic. The airbox and side number plates are now white instead of black, which means that you don’t need white backgrounds to put numbers on the 350 or 450?although 250 riders will need black backgrounds.

(3) Handling. If we were going to hand out a medal to the best-handling bike, we’d give the award to KTM. It may not turn as sharply as the RM-Z, but it doesn’t shake at speed.

(4) Sound. On the FIM’s two-meter-max test, the KTM pumped out a legal 115 dB, and it also passed the AMA’s current 94 dB standard (by the skin of its teeth).

(5) Powerband
. No powerband can be perfect for every rider, but the KTM 450SXF produces the best overall spread of power. It delivers something for everybody?from slow to fast.

(6) Clutch.
This is a bulletproof clutch that will last a rider a lifetime. Better yet, clutch abusers will get it to last longer than any other clutch on the market.

(7) Electric start. Once you try it, you will wonder why every 450 doesn’t have it.

(8) Holeshot device. KTM includes a holeshot device in the crate with every 2012 450SXF.

(9) Brakes. These brakes are better than anything found on a Japanese 450.


No one would have ever dreamed ten years ago that black and orange would be considered stylish…my how fashion sense changes with the times.

Q: WHAT DO WE REALLY THINK?

A: The fact that the KTM 450SXF is relatively unchanged for 2012 might seem like a deal breaker, but since most of its competitors are changed even less, the big Katoom doesn’t suffer by comparison. As the winner of the 2010 and 2011 450 shootouts, the 2012 KTM 450SXF has a high-class pedigree. This is a very good bike…better than three of the four Japanese-made 450S.

facebooktwittergoogle_plusredditmailfacebooktwittergoogle_plusredditmail

Comments are closed.