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Driving report KTM 250 FRR
Counter proposal
With an independent engine concept and a brilliantly presented Hiroshi Aoyama, KTM has established itself as the third power in the 250 World Championship alongside Aprilia and Honda for the second time.
The sensational debut was followed by an equally sudden crash. Donington 2005, pouring rain, in the middle of the 250 lead group a bright orange motorcycle that whipped Anthony West into second place in his first World Cup outing. Tenth place at the Sachsenring and twelve in Brno followed. Then it was over. Technical problems and engine defects increased, KTM pulled the emergency brake and took a break for the remainder of the season to bring performance and stability to competitive levels.
The team around chief technician Harald Bartol has done its homework. With eight podium finishes in 2006, including two wins, and fourth place overall in the World Championship, Hiroshi Aoyama KTM has firmly established itself in the top 250. The special thing about it: At KTM in Mattighofen we go our own way. If the competition is on the road with V2 engines, Bartol relies on an in-line two-cylinder.
First and foremost, because “you can’t automatically get twice the power out of a 250 V2 as from two 125 single-cylinders,” says Bartol, while “the 20 millimeters more width of the in-line engine is not at all significant”. In contrast to the V-engine, the intake and exhaust paths can be designed exactly the same for both cylinders. In shape, length and above all with regard to the same flow conditions. This means that both cylinders can be operated with the same compression and the same spraying. Optimal for the best performance.
In the case of the KTM, that means a good 110 hp, 105 of which reach the rear wheel. Almost even more impressive: the maximum torque of 62 Newton meters. But before they can be enjoyed at the official test date in Valencia, the test driver has to fold himself up properly in the format of a normally grown Central European. The high, ultra-short notches bring the knees to ear level, the elbows somehow bend outwards over the folded legs, in between the upper body bends when reaching for the handlebars.
Now let it push and just don’t stall. Done. The endlessly long first gear requires the clutch to slip forever. The right hand dodges the throttle, lets the speed dance between too high and too low, then it’s time. Engaged, the load rolls grumbling out of the pit lane. Not only when starting off, four-stroke calibrated drivers have every opportunity to embarrass themselves. Even in the first corners.
A tiny tug on the handlebars, a gentle thigh pressure is enough, and the little racer in orange hits the hook like a rabbit. Much too agile for pilots who are used to determined the course. At the beginning they poke around the curves, pulling too hard on the handlebars until they get used to the filigree handling. Besides, it is important to always make sure that the right gear is in there. Just don’t let the speed drop too far. One gear is turned out in no time, the next one should be called up in a flash. Before the bend, shift everything back quickly, don’t turn too early, don’t activate the brutally biting steel discs too hard. Bend, straighten, is the speed right? Gas, upshift. It all happens incredibly fast, there are no breaks for breath. It takes two or three rounds for something like rhythm to come in. Oh man, that you can go so slowly with so much effort.
Then finally the home stretch, take a deep breath, full throttle. From 9,000 rpm the twin, which works with a square bore-to-stroke ratio, comes to life, from 10,000 rpm it really grabs and revs up sharply. The helmet sticks to the tank directly behind the windshield, the rev counter right in front of the nose. The screams at 13600 / min for the next gear. Tschak, a quick step on the gearshift lever, and the whole thing over again. The excellently set automatic gearshift interrupts the frictional connection almost imperceptibly, and the gear changes slide smoothly.
At the end of the home straight, the first real test for the two brake discs lurks. Braking point, gas to and ?? due to the lack of engine braking torque, the KTM shoots unchecked towards the turn-in point with the throttle slides closed. Fast. Way too fast. Accordingly, the first grip on the brake is far too hard. The brake calipers brutally hammer their claws into the steel disks so that it briefly lifts the rear wheel off the ground. Release the brake and hit the corner with a pounding heart and a lot of speed.
But slowly things are going well. Just don’t pull the brake lever too high-spirited, let it run quickly into the corners, there is plenty of grip for inclines and cornering speeds beyond good and bad. The extremely sensitive Ohlins dampers are amazingly comfortable. Sure, Grand Prix works driver Aoyama easily weighs 20 kilograms less than the tester. Nevertheless, together with the stiff chassis, this gives a fantastic feeling for the track and a lot of confidence to crash into fast corners. Ultra-direct, incredibly precise.
The handling of the two-stroke saw is fantastic, almost unreally light, and it allows you to untangle every dense network of curves at lightning speed. The KTM responds to every steering command, no matter how tiny, with practically no resistance. It feels like sailing in a frenzy, getting faster and faster around the corners. Racing in its purest form.
From 10,000 rpm the KTM goes down, almost aggressively on the gas. Aoyama likes it that way. Above all, however, we like how smoothly and almost vibration-free the two-cylinder runs. Despite an ignition interval of 90/270 degrees, which has proven to be the best compromise in terms of power delivery and yield. A balance shaft located behind the cylinders, which rotates at the crankshaft speed, is responsible for the almost perfect mass balance.
With injection, the throttle response should be a little finer. Injection? Correct. When it comes to mixture preparation, KTM also goes its own way. Two 39 carburettors take care of the basic supply of the twin with feed, and an injection injects fuel directly into the crankcase. Of course, Bartol remains silent about the exact where and how.
The most important thing, however, is that the injection enables things that are not feasible with carburettors alone under certain load conditions, such as overrun or in the partial load range. Knock sensors in the cylinders can detect and compensate for minor inaccuracies in the spraying. In addition, it is possible to drive much leaner in the partial load range and also to lean individual load and speed ranges in a targeted manner, which improves drivability and torque curve. However, the injection has been causing problems since the Australian GP at Phillip Island, which is why it was not driven in Valencia.
However, Bartol considers a series two-stroke engine exclusively with injection to be unlikely. But not least with their help, KTM should be able to compete in the World Cup ?? especially after the last glamorous season ?? 2007 rank among the top favorites.
Technical data – KTM 250 FRR
engine
Water-cooled two-cylinder two-stroke series-
engine, cylinder inclined 35 degrees forward,
Bore 54 mm, stroke 54.5 mm, displacement 249.6 cm3, approx. 110 hp at 13,000 rpm, torque 62 Nm
at 12200 / min, maximum speed 13600 / min, Ver-
seal 9: 1, two flat slide carburetors, Ø 39 mm,
additional electronic injection into the crankcase, six-speed cassette transmission.
landing gear
Aluminum bridge frame, Ohlins gas pressure upside-down fork, two-arm aluminum swing arm with Ohlins central spring strut, steering angle 66 degrees (adjustable),
Adjustable caster and swing arm pivot point, wheelbase
1350 mm, two 260 mm steel brake discs at the front,
forged Marchesini magnesium wheels, front 3.50 x 17, rear 5.25 x 17, Dunlop slicks, front 125/80 x 17,
rear 165/55 x 17, tank capacity 23 liters, empty weight 101 kg.
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