2011 KTM 350 SX-F: Rider Test

7 Jun 2015 | Author: | Comments Off on 2011 KTM 350 SX-F: Rider Test
KTM 350 SX-F

2011 KTM 350 SX-F: Rider Test


Surprise! It’s not going to wipe the 450cc motocross bike off the face of the Earth. It’s not going to bring in a new era of mid-size engines. It’s not a revolutionary idea.

It’s essentially a niche motorcycle that fills a void.

It’s good and it’s bad. It’s focused and it’s confused. It is, as you would expect from a machine that is trying to meld two worlds, a confused powerband. It is very much a Dr. Jekyll and Mr.

Hyde engine (or maybe two Dr. Jekylls without a Mr. Hyde).  The first personality is from low to mid. Off the bottom and into the mid-range, the 350SXF has a nice torquey feel.

When it is on the track all by itself it feels like a 450, but it runs very much like a 1998 Yamaha YZ400. Smooth, tractable, pleasant and metered. Not fast, but usable.

It feels like a 450—until you ride a 450 at the same rpm range—then it feels like a 350. The second personality shows itself as the engine climbs into the top end. Unlike a 450, the 350SXF makes all of its serious horsepower above 10,000 rpm.

Since it makes its most horsepower as the last rpm is wrung out of the engine at 12,200 rpm, you have to take it to the rev limiter if you want to make the 46.94 horsepower work for you (because at every rpm below max, it makes less and less horsepower). To be successful you have to rev it…really rev it.

KTM says that the 350SXF weighs 230.2 pounds, but on our scale it weighed 237 pounds (without gas—which is how they are weighed by the FIM and AMA). In a perfect world, the 2011 KTM 350SXF would weigh 220 pounds. Why?

Because that is the minimum weight limit for a bike in the 450 AMA National class. Additionally, the inherent philosophy of building a mid-sized 350cc engine is that you can put it in a 250 frame and compensate for the loss of horsepower with a lower overall weight. At 237 pounds, the 350SXF is not light. Why?

Let’s assume that the typical 250F weighs 220 pounds. To make it into a 350SXF, you have to add in the beefed-up engine components, steel clutch basket, stronger frame and larger rear tire. That is conservatively about 6 pounds more. Next on the agenda is the fact that fuel-injected bikes typically weigh about 3 pounds more than a carbureted bike because of the electric fuel pump, thicker gas tank and added magnets of the magneto.

Finally, KTM elected to mount an electric starter on the 350SXF. And, even though the KTM 350SXF starter motor is slightly smaller than the 450SXF unit, there are still the issues of the battery, starter gear and starter itself. All this weighs about 5 more pounds (because you get to deduct the weight of the kickstarter, kickstarter gear and idler gear). The total weight gain is 14 pounds.

When you add 14 pounds to 220 pounds, you get a ballpark figure of 234 pounds. By this calculation, the 2011 KTM 350SXF is about 3 pounds heavier than it should be. For comparison, the 2011 KTM 450SXF weighs 242 pounds.

The 5 extra pounds are attributed to the 450’s larger cases, bigger crank and longer frame rails.

Every MXA test rider loved the accurate feel of the 350SXF. Once we resolved issues with the fork and shock spring rates, we were able to raise the fork height to select the amount of turn-in we wanted. Once you get the balance right, this bike corners like it’s on rails. We know for a fact that the 2011 Suzuki RM-Z450 turns sharper, but it sacrifices straight line stability for quickness in the tight stuff.

The KTM is a better all-around chassis—it turns, but it doesn’t make sacrifices in your name at speed. The 2011 model is much sleeker, smaller, lower and narrower-feeling at the top (and KTM was smart enough to keep the footpegs far enough apart to offer a firm stance in the rough stuff). KTM went from the bottom of the heap to the top by making small changes every model year.

A lot of the credit may well go to the tunability of steel frames when compared to cast or forged aluminum frames.

Who Would Likely Buy the KTM 350 SX-F:

Given the way that the KTM 350SXF demands to be ridden, which we will get to in detail in a minute, it is not a plug-and-play replacement for a 450cc motocross bike. The 350SXF and its sibling, the 450SXF, are night-and-day different, which is surprising when they share so many components. If push came to shove, we’d say that there are three main buyers for the 2011 KTM 350SXF:

(1) Vet riders: For a Vet class rider who would prefer to race a 250cc bike, but can’t afford to give up 20 horsepower to his 450-equipped competition, the 350SXF offers all the charms of a very fast 250, with the torque curve of a slow 450. Although there are spots on the dyno curve where it gives up as much a 11 horsepower to the 450SXF.

(2) Play riders: When you aren’t bound by any rules, and are just looking for a fun bike to ride, the 350SXF is a little bit like owning a 450 at low rpm and a 250 at high rpm.

(3) 250 transplants: For a kid coming straight out of the 250 class for the 450 class, the 350SXF offers the familiarity of a high rpm, pin it to win it, flat-out 250 four-stroke—without the arm-stretching blast and bulk of a 450.

(1) Gas line quick-release. Thanks to a push-button quick-release, the gas tank can be removed from the frame without any drama.

(2) Optional kickstart. If you want a lighter 350SXF, you can install a kickstarter on the 350SXF. You get to remove the starter, battery and drive gear, but you need to add a kickstarter, kickstart shaft, idler gear and case plug.

(3) Multi-purposing. The water pump, counter-balancer and timing chain gear are all gear-driven from the primary gear.

(4) Fuel tank. At 1.98 gallons of gas, the KTM 350SXF tank is a half-gallon larger than the gas tanks on the Honda, Kawasaki, Suzuki or Yamaha EFI bikes.

(5) Steel frame. The steel frame is 5mm lower than the old frame and 15mm wider at the footpegs; KTM went through 24 different frame variations in rigidity. As for the weight of the chromoly frame, the KTM frame is one pound lighter than any aluminum frame sold.

(6) Steel clutch basket. Although this may seem like a low-tech idea, we loved the steel clutch basket on the 350SXF (it is similar to the basket used in the old-style KTM RFF engine). It will not wear out, and since the clutch spins one-third as fast as the engine and in a reverse rotation, its weight doesn’t add flywheel effect.

KTM used the steel clutch basket becasue it has a thinner profile that allowed the engine cases to be narrower.

(7) Lifting. Finally, KTM has provided a hand hold to lift the bike onto a stand.

(8) Handling. Nothing handles as well as a KTM. Five years ago MXA was saying nothing handled as badly as a KTM.

(9) Sound. On the FIM’s two-meter-max test, the KTM pumped out 115.7 dB. It also passed the AMA’s 94 dB test at 4500 pm.

KTM 350 SX-F
KTM 350 SX-F

(1) Radiator overflow tube. When water spits out of the overflow, the head pipe produces a steam cloud.

(2) Oil filler cap. We had the oil filler cap on the right side of the engine unwind during a moto. We installed a smaller and sleeker KTM accessory filler cap.

(3) Water pump gasket. We knocked the water pump in a crash and dislodged the water pump gasket—causing a major water leak.

(4) Shock preload ring. Hated it. It’s much harder to use than last year’s simple aluminum ring. The new nylon preload ring deforms easily and, for some reason, it is very hard to turn.

KTM says not to hit it with a hammer and punch, but we had no choice.

(5) Gear ratios. They must work for someone, but not us. There is a big gap between second and third.

(6) Weight. This would be an incredible bike at 220 pounds, amazing at 225 pounds, awesome at 230 pounds, but the 237 pounds isn’t a check mark in the “plus” category.

(7) Rims. The Excel rims on MXA ‘s race bike were buttery soft. We chased the spokes with a vengeance. KTM says that they will replace all of the soft rims on the showroom bikes.

Recommendations for Improving the Bike:

(1) Reprogram. We went from the standard ignition curve to the “aggressive” curve. This is ignition timing only, not fuel mapping.

To access the maps you need KTM’s optional adjuster dial ($49.60 from your local dealer).

(2) Gearing. We geared it down one tooth (from 50 to 51), and several MXA test riders chose to gear it down two teeth. The stock gap between gears is too large. With the stock setup, the bike 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. Gearing it down one tooth helps the second-to-third shift and brings the rev limiter into sight.

Gearing it down two teeth makes third gear more usable. The long pull may seem like a good thing, but if you don’t get to 12,2000 you aren’t reaching max horsepower. Translated that means that for every rpm below 12,200 you are losing power.

(3) Exhaust system. We borrowed a Mike Alessi replica Factory 4.1 exhaust system from FMF and it romped. It delivered excellent performance, and the proof was that MXA ’s 52-tooth aficionados returned to 51 teeth because the power carried better.

(4) Springs. Every MXA test rider demanded that we go stiffer on the springs (front and rear).

(5) Locking gas cap. We cut off the tangs on KTM’s irritating gas cap to disable the locking device (if you do it just right, the gas cap will click off and you won’t need to use two hands to open it).

(6) Radiator vent hose. The stock silicone radiator vent hose vents directly onto the head pipe. Bad idea. We installed a longer vent hose that dumped out under the engine.

(7) Oil filler cap . If you wear motocross boots with hinges, the hinges can hook on the black plastic oil filler cap and unscrew it.

KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F
KTM 350 SX-F

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