Review Yamaha YZ 250 F
She hisses and roars ?? the small four-stroke crosser YZ 250 F soon wants to saw the aggressive two-stroke 125 cc with a lot of noise and crazy speeds.
The sound is just crazy: after kicking off a sonorous babbling that turns into a hoarse barking with short bursts of gas? you feel like a fat twin.
If need be, the small five-valve engine can creak up to 13500 tours. For comparison: the four-cylinder of the street sports car YZF-R1 with the same individual displacement already makes the bend at 12,000 rpm. The reason for the extreme turning capacity: The YZ-F is an ultra-short stroke with a stroke of 53.6 millimeters and a 77 millimeter bore (R1: 58/74 millimeters). So that the valve train can cope with these speed orgies, Yamaha donated the 250 ?? as well as the bigger sister YZ 426 F ?? for the first time in series valves made of titanium. A brave step, up to now the light metal valves used in racing were not considered particularly stable.
The 250 F looks like a too hot bathed 426 F, everything in the same place, just smaller, more compact. The engine is constructed in the same way and has a small balance shaft itself. The fact that no identical parts are used differentiates Yamaha from its competitors, some of whom dare to split the displacement between 250 and 650 cm3 on a basis? with appropriate compromises. The individual design of the YZ 250 F enables not only an optimized weight, but primarily a highly specialized engine.
The 250cc Yamaha is exemplary that such effort pays off. First of all, everyone expects either a sapless rubber engine or an extremely aggressive, pointed unit with a small single cylinder. None of that applies, the usable speed range of the YZ 250 F is phenomenal, the punch is impressive in all situations, the controllability is perfect. You stop at between 6500 and 13000 revolutions on the slope. With 38 hp, the YZ-F is only just below the most powerful 125 cc, the torque curve is worlds better. Therefore, the 250 always has plenty of power and a spontaneous bite. The switching work is limited, there are often two gears to choose from.
The easily controllable characteristics are astonishing, which up to now was only known from the weak-chested Kawasaki KLX 250. Whether beginner, amateur or professional, everyone can get along with the mini four-stroke immediately, motocross will be easier and more fun in the future. Even the MOTORRAD photographer produced respectable full-throttle drifts straight away (and that’s saying something). Without ever reacting poisonously, the YZ-F hangs on the gas as if the cerebellum and Keihin were wired directly.
Jokes aside, what about serious motocross? Even a die-hard two-stroke driver has no adaptation problems. The traction is downright incredible. Loose rubble, slippery clay, soft sand ?? all of this can be ignored in the future. It takes a few laps to realize that the throttle can be safely operated digitally. Full on is a simple recipe, unpredictable side effects are excluded. The YZ-F catapults itself out of the bends in a clean drift, while the two-stroke colleague seeks traction with throttle bumps and a skidding rear wheel. The front wheel never comes up suddenly when accelerating, the front section of a 125cc looks considerably lighter. Nevertheless, the four-stroke engine can easily be lifted over holes and edges if necessary.
The 250 weighs 103 kilograms. That’s less than a two-stroke 250, but eight kilograms more than the current 125. Which is rarely noticeable when driving. For example, the engine simply plays hard landings after steep jumps by ignoring any drop in speed. You feel a sense of inertia in stop-and-go corners when the motorcycle has to be heaved around with force. And when accelerating from a standstill, perhaps a little liveliness is missing compared to a 125cc. On cross-slopes outdoors, these minimal deficits hardly negate the torque increase on the rest of the route. The comparison in indoor races should be interesting, where the four-stroke engine cannot easily show its advantages.
The fantastic engine outshines the chassis properties. In contrast to the comparatively rough 426, the smooth running 250 fork and shock absorber put less strain on it. Where the big machine bangs over the stones or prances when accelerating, the 250 quietly pulls its course. The small version doesn’t know anything about the handlebar. Only sometimes when braking hard does the fork bounce back and forth over the holes. A typical Yamaha phenomenon, but one that experienced suspension specialists get a grip on.
KNow everything works as if the 125cc two-stroke would soon be slow-moving. But it doesn’t go that fast. Because while some regional organizations as well as many other countries already want to allow the four-stroke engine in the eight-liter class, the DMSB is initially leaving it with the old displacement regulation after the intervention of the Yamaha competitors. As a result, the YZ 250 F has to compete against two-stroke engines of the same size here in the country, and there it has no chance. So there is still a two-year grace period until the ears of the 125cc two-stroke drivers finally fall off.
Faster than a 125? that is the key question. A KTM SX 125 was used for comparison on three routes, and in terms of power it is the reference among the 125 cc. There was also a YZ 426 F on two slopes. Right from the start, the four-stroke 250 can play out its wide usable speed range. While the 125cc has to shift gear on the start gate, the 250cc pulls forward evenly in second gear. If it is slippery, the 250 will roll into the curve with unbelievable speed and just as undeterred out again, no 125 can keep up. On the stony, quickly marked piste in Figueres, the performance, traction and stability of the 250 add up to a lead of around three seconds. However, the smaller sister has no chance against the rough, strong 426er. In the deep, wet sand in Hagenau, however, the good 250cc time is amazing. Driver Andi Kanstinger was hardly faster with the 426. Deep grooves and waves in front of the bends caused a lot of unrest in the 426 chassis. On the other hand, with the nervous 125 cc, it is difficult to keep the engine in the narrow performance range. The track in Dielheim was less deep, but wet and slippery. On such difficult terrain, the four-stroke engine is immediately easier to move, even by a 125cc specialist. The values mentioned are not necessarily representative and can be transferred to all cross slopes, but they show a tendency. Depending on the route conditions and the driver, other relationships may arise. Basically, the YZ 250 F has a slight advantage in such comparison drives because, in contrast to the two competitors, there are no conversion problems. 2: 07,32: 09,12.07,2Dielheim / D ** 1: xx, x1: xx, x- * Andi Kanstinger ** Max Ritter; Best time of the timed laps
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