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Comparison test 250 cc four-stroke motocrosser

Welcome to the club

Two measures are two too few? now also in motocross. It is understandable that in the 2006 season all manufacturers will finally be offering a four-stroke engine for the 250cc class. And who is the boss?

Germany’s current flagship crosser Max Nagl will be able to confirm this: Since 250 cc four-stroke engines have also been approved in the smallest world championship category, two-strokes such as Nagl’s KTM 125 SX have been seen as having no chance. Equal in top performance, the bonsai shooters play their screaming colleagues with much better draft in particular
lower speed range and, accordingly, easier drivability against the wall.
Because it’s not just about honor on a higher sporting level, but above all about decent sales figures in this still young league, the manufacturers are currently not spoiling for development efforts for the Production Racer. Honda developed the im
CRF 250 R presented in 2004
a double silencer system, higher
Compression and a 40 instead of that
previous 37 carburetor continued. The Kawasaki KX 250 F, which was also presented in 2004, has been massively revised with a brand new bridge frame made of aluminum profiles instead of the oval steel tubes used since then, as well as a new rear swing arm, Showa instead of the Kayaba suspension elements previously used and higher compression. The technicians from Mattighofen put their first work on the subject of quarter-liter four-stroke crossers on the
Bikes. The KTM 250 SX-F (driving report in MOTORRAD 18/2005), which was delivered in limited numbers during the 2005 season, is the only one in the test field that still uses a single-loop steel frame with the KTM-typical, direct approach
The suspension strut hinged to the swing arm, while the engine, which was introduced with much advance praise, is largely based on the concept of the competition thanks to the dohc valve train and compact dimensions.
The Yamaha engineers also put a lot of effort into the YZ 250 F, which they presented for the 2001 season as the pioneer of the 250cc four-stroke class
Have a general overhaul. A completely new single-loop frame in which aluminum replaces the previous steel tubes, right? first time in motocross-
Series machine construction ?? a shock absorber spring made of titanium update the YZ fundamentally in addition to the usual fine work. How keen the competition is in this class is shown by Suzuki (see box on page 55), whose 2006 model is not even in the-
is ported.
But technical finesse and new concepts are only measured by one thing, by results. Even if people still have that on the bumpy slopes
plays a greater role in the success than the material, but in the four-stroke class with the lowest displacement, there is no substitute for performance. Not only does Dietmar Lacher, six-time German motocross champion, former world championship top pilot and opinion-forming permanent guest at all MOTORRAD motocross tests know that.
Already on the way from the paddock to the track ?? the tests took place in Mothern, France, as well as in Frankenthal and Walldorf ?? the 2006 season announces acoustically. After the noise limit in motocross has been reduced from 98 to 96 dB (A) in the coming season, the engines are not babbling
significantly, but audibly quieter than before. Only the KTM is still well above the new limit. Which can bring you problems later not only with the technical acceptance, but also with your owners who are forced to retrofit. Because four-stroke singles usually react to reduced noise levels with poorer responsiveness in the lower and middle speed range.
Didi is already pounding the slopes with the Honda. So far, the CRF has applied
as a problem child in this class
the engine power. Especially in the upper speed range there was a lack of the red one
of revving and usable performance. A fact that was attributed to the unicam valve train, which is too sluggish at five-digit speeds, which actuates the intake valves directly with a single camshaft and the exhaust valves via a fork rocker arm. The fact that the Honda engineers are aware of the problem is proven by the stately one from 37
40 millimeters larger carburettor diameter and the double exhaust system, which is supposed to provide for free exhaust disposal. But the rescue operation remains without resounding success. The most compact drive in the field turns in practice in the partial load range from mid-speed onwards rather cautiously? even if the
The performance curve determined on the dynamometer under full load (see page 55) suggests a connection to the competition. Upshifting early, often a solution in the 450 class for engines of this type, is of little help in the 250 class. So the CRF tackles the exit of the bend, but can no longer extend its lead on the next straight.
For example the one before the Yamaha. The trendsetter of the quarter-liter four-stroke engine remains true to its character in the new aluminum frame. The blue one pushes out
Sweeping on robust, pushes forward vehemently. Open the gas and the YZ 250 F runs. And
what the Honda didn’t like, the Yamaha demands: shift up early. Because
further up the punch flattens noticeably, the rev limiter warns to change gears. What the Yamsel can easily lift, but from the pilot an active shift foot and ?? because of the difficult clutch? requires a powerful left hand.
The weakness of the Yamaha drive? To have to shift on short intermediate straights instead of turning off the gears ?? belongs to the domain of the KTM aggregate. The engine concept in which the two camshafts drag the valves-
operate the lever proves to be be-
impressively easy to turn. Designed without a speed-inhibiting balance shaft and, on top of that, briefly translated, the KTM single climbs up the speed ladder in a flash to deliver additional thrust up to the highest regions. Yet:
Plenty of traction, which prevents the slip on the rear wheel from increasing the engine speed in non-slip, moist sand or clay
increases rapidly, the Austrian engine takes this advantage. Then the one with the longest stroke loses the
Gang of four gave the 250 SX-F its bite and struggled with torque weaknesses noticeably more laboriously over the speed scale.
A quirk that the Kawasaki has-
Single cylinder is foreign. Although its base still comes from the joint development between Kawasaki and Suzuki, the green troop managed a masterpiece. Record-breaking compression, sharp control times and ?? first-
times with a series crosser ?? on and off meticulously reworked by hand-
Lass channels pack up huge mountains of muscles for the hitherto good sportsman. No one else is as directly attached to the gas as the Kawasaki single, so perfect-
Nobody shares their power over the entire speed range.
Which would already lay the foundation for success or defeat. Because ?? we remember ?? Performance is
also in the low-displacement segment
Difficult in motocross by others
To replace qualities. Even if, like KTM, you set clear priorities. We
The Austrian is looking for narrow, supercross-like slopes with ultra-sharp handling and a front brake on top of that,
that sets standards, namely
their own kind. Less on fast slopes. The SX-F demands commitment from the pilot in order to keep on course
stay. Only then did
also the directly linked
White-Power-Strut open to the competition in terms of traction and, above all, in terms of behavior when braking. The KTM 250 SX-F continues to acknowledge lazy use of the trainer with an uneasy response
Fidgeting. Topic front wheel guidance: The
White Power’s upside-down fork can now at least compete with Kayaba products.
Whose flag is Yamaha now the only one to hold high. Both strut and
Forks show themselves grown in large holes, but do not have the punch reserves for jumps or the sensitivity for smaller waves like the Pendats from Showa. Yet:
Despite the new aluminum frame, the Yamaha remains true to its chassis, too. a bit top heavy? Steer precisely with the front wheel and lies like a board on fast straights.
Back to the Honda: Especially those
The coordination of the Showa spring elements deserves the title valuable. Whether the highly sensitive response to small waves or the buttery smooth march through the spring deflection in brutal landings, the Honda uses shock absorbers and
Gabel clearly set the standard. Especially since agile handling is one of the strengths
belongs to the highly balanced CRF. Strange: the front wheel brake from supplier Nissin, which has also set standards up to now, got on the current CRF 250 R.
into a form depth. The delay performance is well below that of the predecessor-
models and the competition.
What the Kawasaki is spared.
Whether the sensitive Nissin brakes that ?? despite hard shock absorber spring ?? only compared to the examples in the Honda marginally less sensitive suspension tuning of the Showa elements, the tight straight-line stability or the more generous ergonomics compared to the competition ?? The Kawasaki is clearly the new drive of the development department. Tea KX 250 F looks so grown up and
that they are mature in terms of handling
can confidently give way to a few colleagues ?? knowing full well that none of you can dispute the overall victory.

Comparison test 250 cc four-stroke motocrosser

Welcome to the club

Technical data: HONDA

Honda
Water-cooled single cylinder-
ohc four-stroke engine with four valves
249.4 cm3
78.0 x 52.2 mm
12.9: 1
26.8 kW (36.5 PS)
10700 rpm
Keihin FCR
40 mm
5

Bridge frame made of aluminum with screwed-on stern
aluminum
Showa
47 mm
Showa
99.0 kg

7.410 euros

Technical data: KAWASAKI

Kawasaki
Water-cooled single cylinder dohc four-stroke engine
with four valves
249.0 cm3
77.0 x 53.6 mm
13.5: 1
27.7 kW (37.7 PS)
10800 rpm
Keihin FCR
37 mm
5

Bridge frame made of aluminum with screwed-on stern
aluminum
Showa
47 mm
Showa
98.4 kg

7565 euros

Technical data: KTM

KTM
Water-cooled single-cylinder dohc four-stroke engine
with four valves
249.5 cm3
76.0 x 55.0 mm
12.8: 1
27.8 kW (37.9 PS)
11500 rpm
Keihin FCR
39 mm
6th

Single-loop frame made of steel with screwed-on rear
aluminum
WP
48 mm
WP
101.0 kg

7740 euros

Technical data: YAMAHA

Yamaha
Water-cooled single-cylinder dohc four-stroke engine
with five valves
249.0 cm3
77.0 x 53.6 mm
12.5: 1
27.0 kW (36.8 PS)
10800 rpm
Keihin FCR
37 mm
5

Grinding in-
frame made of aluminum with attached-
screwed aluminum stern
Kayaba
48 mm
Kayaba
101.2 kg

7,750 euros

Test result: HONDA

Knapp: perfect suspension coordination, top ergonomics, great workmanship. Tea
Honda has what it takes to be a test winner? if the engine showed more life

Test result: YAMAHA

Who would have thought that?
Great suspension, powerful engine, great brakes ?? no crosser looks so homogeneous
like the new Kawasaki. A winner without weaknesses

Test result: KTM

Not for lazy boys:
Whether suspension tuning
or engine ?? the new KTM works tremendously when
she is driven with dedication. If not, then don’t

Test result: YAMAHA

Typical Yamaha:
Punch off the shoot-
pay cellar, more stable
Straight ahead, pressure
on the front wheel.
Some things never change? neither
with aluminum frame

Without yellow?

Together we are strong. After this
Motto, Kawasaki and Suzuki joined forces in the development of the first 250cc four-stroke crosser in their respective company history, presented for the 2004 season. The co-production was on offer for two years, until the marriage of reason was divorced. While Kawasaki is taking flight forward with the current KX 250 F, Suzuki is holding onto the previous one
Model fixed. Despite the facelift, the RM-Z has not been able to improve the image damaged by overheating and transmission problems as well as the wear-prone valve train. That is why the 2006 RM-Z, which technically differs only marginally from the 2005 version, is not officially imported into Germany ?? and is therefore left out in the comparison test of the 2006 four-stroke crosser. Bargain hunters can still look forward to it. Tea
The list price of the RM-Z 250 (2005 model) has been reduced to 5490 euros, the
Yellow already offered under 5000 euros.

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