Driving report Yamaha YZ 450 F-YZ 250 F

Driving report Yamaha YZ 450 F / YZ 250 F

Harvest time

For years they had plowed the four-stroke soil, sown it carefully, tended it with love. Now Yamaha wants to reap the harvest with the new YZ 450 F and the revised YZ 250 F..

In the winter of 1996/1997 ?? actually not that long ago ?? Yamaha announced that it would compete against the powerful two-stroke engines in the 500cc Cross World Championship with a four-stroke engine measuring just 400 cm3.

David versus Goliath ?? the unequal battle has since caused a sensation in the offroad industry. At that time hardly anyone suspected the long-term perspective of the four-stroke engine. In the meantime it is already history that these have completely taken over the scepter in the largest class, half-liter two-stroke engines are now extinct. The final breakthrough of the four-stroke engines is still to come, however, because in 2003 they were allowed to turn the tables: 250 four-stroke versus 125 two-stroke, 450 versus 250-stroke.
Right now, the work of the blues should pay off. All the more annoying that Honda presented the more modern, lighter and more powerful machine this year with the CRF 450 R. Therefore, Yamaha prescribed the “oldie” YZ 426 F a radical fitness regimen: building muscles and losing weight was the usual recipe for such form crises. In plain language: more displacement, consistent lightweight construction.
The engine is practically new. For the first time, a cylinder head was specially designed for the titanium valves that were already in use. They dissipate heat better, which is why they are now in shorter tours. In search of the excess grams, the technicians devoted themselves to little things like the clutch cable. Apparently they just overlooked the stale steel handlebar. All in all, it still makes a credible five kilograms, which would correspond to a ready-to-drive weight of 106 kilograms. The aluminum-framed CRF, weighing 106.5 kilograms according to MOTORRAD measurements, seems defeated? in this discipline.
More is needed to win overall. MOTORRAD was able to gather first impressions of performance on the fast GP track in Asti / Italy. The new YZ-F look more modern because of the flatter tank-seat combination. And finally Yamaha has recognized the deterrent potential of the cumbersome start-up procedure. The new automatic decompression system, which has long been required, makes it easier for two-stroke drivers to switch. Even the first few meters on the grippy, wonderfully groomed slope make it unmistakably clear where the path in the new displacement category is leading. Torque is the order of the day, sheer power from the low revs. Gone are the days when less well-trained amateurs enjoyed the gentle character of a YZ 400. The Yamaha now pulls your arms out from idle speed.
The 450 is by no means an overpowered monster. On the contrary, the linear characteristic can inspire. The sudden kick in the middle, which sometimes made the old YZ difficult to tame, is leveled under a mountain of torque. At the top there is not a big difference, you can still leave the aisle in for a longer time if necessary. More power, more aggressiveness, more noise – that arouses curiosity about the first comparison with the archenemy CRF. Incidentally, the new four-speed gearbox harmonises perfectly with the broad power range in every situation; three gears would be sufficient on most routes.
Thanks to the direct, lively drive, the top-heavy, somewhat sedate, but also well-behaved 426 feeling is a thing of the past. Not only that of the driver, but also the chassis is subject to much greater stress due to the powerful, harder characteristics. The 450 fights more for traction when accelerating, and on the brakes the fork can get into trouble. The full feeling is gone, lighter machines are basically more nervous. The bottom line is that losing weight brings drastic benefits. The new YZ can be folded down more easily and looks more playful when jumping. The neutral steering behavior typical of Yamaha was retained, and the precision is excellent.
Compared to the explosive 450, the only slightly revised one looks YZ 250 F almost like a toy. She is also said to have lost another one or two kilos. But more important is the flatter tank and the improved seating position. At least in the small category, the Yamaha harvest will certainly be plentiful: There is hardly any serious four-stroke competition in the 125/250 class in the coming year.

What’s new? – Yamaha YZ 450 F

YZ 450 F Larger displacement (449 cm³), longer stroke (95 x 63.4 mm) Seven millimeters flatter, smaller cylinder head Shorter titanium valves; smaller valve springs flatter piston; thinner piston pin, crankshaft 20 percent lighter, four-speed gearbox, longer primary gear ratio, smaller oil pump; lighter ignition rotor clutch with rubber shock absorbers instead of steel springs aluminum oil lines titanium manifold and silencer with aluminum casing lighter clutch cable wheelbase shortened by five millimeters YZ 250 and 450 F smaller timing chain tensioner; Automatic decompression hot start lever on handlebar ignition coil in spark plug connector; smaller ignition black box, better dirt-sealed carburetor, flatter tank-seat combination; smaller tank (7 liters) 1.5 kg lighter frame with reinforcements made of high-strength steel; Lighter rear frameRear suspension with new lever geometryLighter rear brake with integrated reservoirLighter front brake with aluminum pistonLighter, anodized swingarmReinforced upper triple clampAirbox with better sealingMotor protection made of aluminum / plastic

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