Comparison test: Motocross concept comparison

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Comparison test: Motocross concept comparison
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Comparison test: Motocross Suzuki, KTM and Honda

Motocross concept comparison: 250, 350 and 450 cm³

With the 350 SX-F, KTM wants to combine the performance of a 450cc machine with the handling of a 250cc bike. Can the completely redesigned 350 really fill the gap between the traditional displacement classes so attractively?

D.Three prerequisites were necessary to get those responsible for KTM up to the idea of ​​the 350 SX-F. First, the realization that in the Motocross World Championship the lap times of the MX2 class (250 cm³) and the MX1 category (450 cm³) are now at a similar level. Secondly, the conclusion that the logical consequence of a MX1 crosser that is overpowered for many pilots and a handy MX2 bike that requires speed would have to be a machine with 350 cc. And third, the fact that the technical regulations, which stipulate a displacement between 290 and 450 cm³ in the MX1 league, would allow the 350cc concept in this premier class.

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Comparison test: Motocross concept comparison

Comparison test: Motocross Suzuki, KTM and Honda
Motocross concept comparison: 250, 350 and 450 cm³

RM-Z 250 and the Honda CRF 450 R have to answer.

On three different tracks and uniform tires (Bridgestone M 403/404) the newcomer has to prove his strengths in the criteria by which this concept is measured (pulling power, revving, top performance, handling, sprint qualities at the start). And the new rear suspension with deflection must also show its colors. Ready to go.


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Captain Future? Who knows, KTM could write motocross history with the 350 SX-F. In any case, one thing is already certain: the 350 is definitely one of the most user-friendly motocross machines.

START
A big plus for the KTM. The standard electric starter is easy on your nerves and your stamina in the event of accidental braking or slipping. The 1.5 kilogram extra weight (electric starter plus battery) is gladly accepted in seconds of need. It is surprising that all Japanese crossers are still missing out on this chance.

DRAFT
First of all: Keihin’s battery-free petrol injection, which has meanwhile developed into a standard mixture preparation for all Japanese manufacturers, also works without any problems in the KTM. Excellent starting behavior, no swallowing when the gas ruptures or after jumps – the Austrian engine also shines with these qualities.

And how does the 350 get out of the corners? The pressure starts much earlier than with a 250, but still gentler than with a 450. In the blind tasting one would rely on an exceptionally easy to control 450 cm³ engine. That has advantages. While the Suzuki driver always looks for the track with enough momentum, the Honda driver looks for the best line at least on hard terrain, the 350 trainer is free to choose. Above all, the inner line, which is often difficult to drive in the acceleration phase, but is shorter, should become the first choice of the SX-F pilot thanks to the excellent controllability of the power. Only in the sand does the CRF stay on par with the KTM in terms of traction and can even easily distance it in deep terrain. Nevertheless: If one aspect documents the promised perfect compromise of the 350cc KTM, it is this impressive traction, which makes the KTM easier to control on any terrain and – especially when the condition is declining – significantly more efficient than the two traditional displacement sizes. However, the early onset, good-natured thrust of the 350 belies one thing: the KTM wants to be turned for fast lap times. The single only develops the decisive punch for this from the middle speed range. But then huge.


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Eckenwetzer: Agile handling is the strong point of the 250cc Crosser. Mainly thanks to the low rotating masses (light crankshaft), the objectively hardly lighter RM-Z becomes a flyweight on the slopes.

FILMING PLEASURE AND TOP PERFORMANCE
With a maximum speed of 12800 / min (maximum speed RM-Z 250: 13300 / min), the SX-F not only advances in speed regions that were previously reserved for 250 engines, but also overtakes the CRF 450 R in terms of top performance. With measured 52 PS (Honda CRF 450 R: 49 PS) the KTM convinces even skeptics all along the line. In addition, this enormous speed reserve makes it possible to forego a gear change regularly, especially on intermediate straights, while the comparatively late Suzuki and the Honda, which reach their performance peak very early, almost always need an additional shift. The enthusiasm for this sensationally wide usable speed range, however, initially clouded the uncomfortably rough running engine on higher tours. A customer machine driven against it for comparison showed the same phenomenon. Only when a crankshaft with finer balancing was implanted in the factory did the SX-F behave decently. In series production, KTM wants to remedy this with improved quality control.


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Discontinued Model? The Honda proves that the 450 class is still viable even after the attempted coup by the 350 KTM. The Honda can make use of its superior torque when starting, on jumps with a short run-up and on high-traction surfaces.

HANDLING
You know it: 250cc Crossers feel worlds lighter than their 450cc sister models. What makes the difference It can hardly be due to the total weight (Suzuki: 102 kilograms, Honda: 105, KTM: 106). The rotating masses are more decisive, especially those of the crankshaft (Suzuki: 2810 grams, KTM: 3490, Honda: 4030). It is understandable that the Suzuki therefore sets the tone when it comes to handling. In comparison with the playful lightness of the RM-Z 250, even the Honda, which is basically also quite handy, loses a lot of ground. And the KTM? Squeezes on a high level with inconspicuous handling exactly between the 250 and 450. However, with one caveat: in tight turns, the front tends to understeer and pushes towards the outside of the bend. At least in the standard trim, the steering precision of the KTM does not reach the level of the Suzuki or Honda. A raised rear (negative spring travel with driver: 95 millimeters) and fork legs inserted deeper into the triple clamps (two rings visible) alleviate this tendency, but still do not give the SX-F the razor-sharp steering behavior that is familiar from previous KTM models.

SUSPENSION
Speaking of previous models. If the previously installed, directly linked PDS shock absorber always required an active pilot, the new system reacts much more comfortably. The Monoshock swallows small waves sensitively, irons hard edges as smoothly as possible and, above all, keeps the rear under control, especially with many driving errors. You were not used to that from previous KTM crossers either.

And it confirms that the KTM 350 SX-F can not only be reduced to the displacement of the golden mean, but is the result of the search for a new overall concept for the Crosser from Mattighofen – a largely successful one.

CONCLUSION


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The KTM SX-F 350 achieves top performances and points the way to a reorientation among the KTM crossers.

With the 350 SX-F, KTM achieved a start-to-finish victory in the plan to combine the advantages of two displacement categories, at least with the engine. Responsiveness, revving and top performance do indeed combine the best of both worlds. If you add the new, more sensitive rear wheel suspension and the good-natured driving behavior to this component, however, this new concept proves more: a general reorientation of the KTM crossers.

Readings


Drawing: archive

Power on the crankshaft. Measurements on Dynojet roller test stand 250, corrected according to 95/1 / EG, maximum possible deviation ± 5%

Hats off: The fact that the 350cc KTM with no less than 52 hp even outshines the 450cc Honda in terms of performance is astonishing even for experts. Nevertheless: The Honda’s larger displacement is reflected in the torque. An advantage that the CRF knows how to implement right from the start.

A successful start is half the battle, says the racing driver vernacular – and he is right. Toni Cairoli already dispelled this doubt with several start-to-finish victories that the 350s could be inferior to the 450s in the sprint. But what about the sprint qualities apart from reaction times and the courage to brake late? MOTORRAD made the test. The experimental set-up: grippy, sandy ground, length of the starting straight 60 meters, recording of the measured values ​​via GPS-supported data recording.

The results are clear. The 450 Honda is clearly ahead of the 30-meter mark, and the 350 SX-F distances itself by 3.4 meters to the braking point at 60 meters. The reason is likely to be found in the higher torque of the 450 engine in the range of up to 7000 rpm (see diagram), which the Honda – provided that the clutch is used carefully – enables a head start from a standing start.

Acceleration up to 60 m

   30 m  60m
Honda CRF 450 R.  68.73 km / h  90.81 km / h
KTM SX-F 350  64.4 km / h  84.64 km / h
Suzuki RM-Z 250  62.0 km / h  76.48 km / h


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Brilliant: The injected RM-Z 250 engine.

Suzuki RM-Z 250

engine
 
Water-cooled, single-cylinder, four-stroke dohc engine with four valves per cylinder
 
Displacement (in cm3) 249
Bore x stroke (in mm) 77 x 53.6
compression 13.5
Power* 29.2 kW (40 hp)
at speed (in / min) * 12600
Carburetor / injection, injection
Diameter (in mm) 43
Corridors 5
landing gear
 
Bridge frame made of aluminum
 
fork Showa
Guide tube diameter (in mm) 47
Strut Showa
Weight in kg)* 102
Price without additional costs (in euros) 7190


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The Dohc unit of the KTM 350 SX-F exceeds all expectations.

KTM 350 SX-F

engine
 
Water-cooled, single-cylinder, four-stroke dohc engine with four valves per cylinder
 
Displacement (in cm3) 350
Bore x stroke (in mm) 88 x 57.5
compression 13.5
Power* 38.0 kW (52 hp)
at speed (in / min) * 12600
Carburetor / injection, injection
Diameter (in mm) 42
Corridors 5
landing gear
 
Single-loop frame made of tubular steel
 
fork WP suspension
Guide tube diameter (in mm) 48
Strut WP suspension
Weight in kg)* 106
Price without additional costs (in euros) 8395


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Compact: The Honda engine of the Honda CRF 450 R with Unicam valve train.

Honda CRF 450 R.

engine
 
Water-cooled, single-cylinder ohc four-stroke engine with four valves per cylinder
 
Displacement (in cm3) 449
Bore x stroke (in mm) 96 x 62.1
compression 12th
Power* 36.1 kW (49 hp)
at speed (in / min) * 9750
Carburetor / injection, injection
Diameter (in mm) 50
Corridors 5
landing gear
 
Bridge frame made of aluminum
 
fork Kayaba
Guide tube diameter (in mm) 48
Strut Kayaba
Weight in kg)* 105
Price without additional costs (in euros) 7910

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