Yamaha has moved to the twin-spar design and it has led to changes all around the bike as a result.
Yamaha has unveiled a totally new 250cc motocross bike with the 2010 YZ250F, but it isn’t radical in the way we expected. Rather than jump on the fuel injection bandwagon, which it hasn’t done with the YZ450F yet or any other Yamaha dirt bikes
, Yamaha turned its smallest 4-stroke YZ-F inside out with a redesigned chassis – somewhat literally, actually.
Yamaha has been different from the other Japanese OEMs with its backbone aluminum chassis, but for 2010, the Tuning Fork Company has joined the ranks of twin-spar design. The “bilateral beam frame” looks similar to what you will find on Honda
and Suzuki dirt bikes
, but the chassis spars are not the same. With 20 pieces of forged and extruded alloy, the chassis has moved the head pipe rearward 7mm and down 12mm. Rake and trail adjusts to 27.5 degrees and 120mm and Yamaha claims that the overall package was changed to focus on a better rigidity balance. With the new frame layout, much of the YZ250F was able to be reworked, including the suspension, motor and bodywork. The fuel tank now holds the smaller 1.7 gallons of fuel between the spars rather than around the sides of the main backbone, helping to center and lower the weight.
Rider input is stronger thanks to the new layout and turning ability is supposedly much more agile.
Because the radiators are moved rearward with the changed steering head, they are narrower to keep the bike the same width between the knees, but thicker to retain capacity. The airbox and boot is redesigned for a straighter intake, and the Kayaba shock spring is 30mm lower to help make room for it. Shock internals are updated as are the settings for the KYB speed-sensitive fork. Yamaha claims the new geometry and suspension settings allow the extra rigidity in the new chassis to be transferred to the suspension and makes the bike easier to handle in corners. Aiding in the handling department is the rider position. The new fuel tank, flatter seat, higher footpegs and the lower/rearward steering head put the pilot forward and increases pressure on the front end.
We’re at the track today pounding laps around Washougal Motocross Park to see if the chassis changes are all they’re claimed to be. The bike certainly looks amazing with totally new bodywork and the snazzy chassis – it’s by far the baddest looking YZ-F we’ve seen yet. Stay tuned for the results of our first ride with photos and video early next week.
2010 Yamaha YZ250F Specs:
The airbox is reshaped to allow for a straighter intake and the exhaust handles spent fuel.
Engine Type: 250cc liquid-cooled DOHC 4-stroke; 5 titanium valves
Bore x Stroke: 77.0 x 53.6mm
Compression Ratio: 13.5:1
Fuel Delivery: Keihin® FCR MX37
Transmission: Constant-mesh 5-speed; multiplate wet clutch
Front Suspension: Speed-Sensitive System inverted fork; fully adjustable, 11.8-in travel
Rear Suspension: Fully adjustable single shock; 12.0-in travel
Front Brake: Hydraulic single disc brake, 250mm
Rear Brake: Hydraulic single disc brake, 245mm
Front Tire: 80/100-21
Rear Tire: 110/90-19
L x W x H: 85 x 32.5 x 51.3 in
Seat Height: 38.9 in
Wheelbase: 57.7 in
Ground Clearance: 14.8 in
Fuel Capacity: 1.7 gal
Claimed Wet Weight: 224.8 lb
Colors: Team Yamaha Blue/White; White/Red
MSRP Info Available in September, 2009