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while we were expecting for fuel injection, YZ250F comes with a Carburettor., This motor gets better breathing, lighter valve-train components, more efficient combustion and a new exhaust system starting at the cylinder head porting.

Bottom end improvements range from new gear ratios and strengthening as well as clutch leverage and spring rate changes.

Interestingly, the power improvements across the boardare designed, and this is a direct quote, to, "Improve power while reducing noise."

New Airbox shape

This is designed to straighten and smooth the intact tract from air filter to carb. The smoother and straighter the path from air to fire, the better-especially for fuel injection (which we expect to see next year on the YZ250F. The entire air filter is shifted to the left 10mm.

Continuing the straight-shot air management, Yamaha designed an all-new carbUrettor body.. The accelerator pump cam is changed for quicker fuel delivery. Also, the jetting is changed to the richer side of things. Yamaha is going for a good "torques" feel at low RPM while delivery the best response possible under quick openings.

The YZ250F's intake cam profile is changed for better low end to mid-range power and response. The Yamaha YZ250F took a little beating in the past from the press for being a bit sleepy on the bottom. Maybe this will silent that. The cam now has 7.7mm of lift versus the 7.6mm from last year while maintaining the same cam timing. That means the valves are opening a bit more but opening at the same time-basically. There is a hard surface treatment applied to the very top of the valve stems, too. Yamaha's proven YZ250F valve durability should see an improvement with the fancy hromium Nitride coating.

Valve Spring Retainer Changed From Steel to Aluminium:

Lighter is better and with the reduced load on the spring thanks to the Aluminum retainer, the spring rate can also be lightened. The intake spring load is reduced 12% and the Exhaust spring load is reduced 9%. Reduced friction and better low-end to mid-range power and response are the goals.

Yamaha wants its exhaust gases to have more velocity so it shrunk the exhaust port into a D-shape. Guess why. Yep, for better throttle response.

Yamaha went back to (after going away from) a two-step mid-pipe for 2010. It steps up from 45 mm to 50.8 mm right after it attaches to the frame. Further back the muffler grows 50mm and gets a reduced core diameter. Inside, the "pipe perforation pitch" (meaning the amount of holes, really) changed from 4-5mm. That means the less holes and they are farther apart. The muffler mount changed from rubber to solid metal-on-metal. All this to reduce sound without reducing power from the new Yamaha YZ250F.

Clutch Modes:

Internally, Yamaha YZ250F clutch basket center boss gets hardened material for more durability and the clutch arm ratio and clutch spring load are both increased. The result? Easier lever pull (3% easier) with stronger engagement and wider engagement area feeling. That means less herky-jerky clutch on-off action.

Gear strength is increased in 3rd, 4th and 5th gears with 3rd and 4th getting a slightly taller ratio. That's like a half tooth difference on a rear sprocket. There is also some revision to the drive dog shape. Stronger, better engagement is what Yamaha is looking for here.

Ignition mapping is changed to match all the intake and exhaust specifications for the 2010 Yamaha YZ250F.

The 2010 Yamaha YZ250F radiators mount 15mm lower and 10mm farther back than 2009. Also, the hose routing changes and the mounting points increase from two to three. This makes stronger radiators without the external bracing we've seen in the past.

PRICE---3,60,000 SPECIFICATIONS
Engine Type	Single-Cylinder
Cylinders	1
Engine Stroke	4-Stroke
Cooling	Liquid
Valves	5
Valves Per Cylinder	5
Valve Configuration	DOHC
Compression Ratio	13.5:1
Starter	Kick
Fuel Requirements	Regular
Fuel Type	Gas
TRANSMISSION:
Transmission Type	Manual
Number Of Speeds	5
Primary Drive (Rear Wheel)	Chain
WHEELS & TIRES:
Front Tire (Full Spec)	Bridgestone® 80/100 R21
Rear Tire (Full Spec)	Bridgestone® 100/90 R19
BRAKES:
Front Brake Type	Hydraulic Disc
Rear Brake Type	Hydraulic Disc
TECHNICAL SPECIFICATIONS:
Wheelbase (in/mm)	57.7 / 1465.6
Fuel Capacity (gal/l)	1.7 / 6.4