It's a no-brainer to pair these two Yamaha bad boys together as they both boast significant changes for '06. They both have raw, race-ready power, and stunning handling; liquid-cooled 449cc five-valve engines; and performance-oriented five-speed transmissions. That leaves only one question: Do you prefer two wheels or four wheels with your 449cc engine?
The YZ name has been around, like, forever. Naturally, you can imagine the Yamaha engineers sweating bullets when it came time to improve on this legendary name. For '06 they started with the heart of the bike by designing an all-new frame. This frame is light and strong and is an extensively tested combination of castings, extrusions, forgings, and aluminum tubing. It includes a removable aluminum rear subframe that lightens the overall weight and provides for easy maintenance. The new frame also repositions the engine for what Yamaha says is great mass centralization, which is another contributor to the YZ's improved overall handling.
Speaking of the engine, the 449cc powerplant has been significantly redesigned for '06 to make it produce more power, improve its overall balance and handling, enhance its durability, and run cooler. Some of the changes include carburetion and exhaust changes; a redesigned piston, crankshaft, and connecting rod; revised CDI ignition; redesigned cylinder head angle; and a new oil jet at the bottom of the piston. A number of engine items have also been redesigned to make the engine lighter overall.
The suspension was also upgraded to provide better performance and includes a speed-sensitive 48mm Kayaba fork and a titanium-sprung four-way adjustable rear shock with 2mm larger diameter.
Bottom line: The new YZ450F is an aggressive bike for aggressive riders, and now it's even better. This should make the 250cc motocross class interesting, indeed.
Model: YZ450F
MSRP: $6,899
Engine type: 449cc, liquid-cooled, five-valve, DOHC, four-stroke with titanium valves
Bore x stroke (mm): 95 x 63.4
Compression ratio: 12.3:1
Carburetion: 39mm Keihin FCR flat-slide with throttle position sensor
Ignition: Digital CDI
Transmission: Constant-mesh five-speed
Final drive: #520 chain
Front suspension: 48mm Kayaba inverted telescopic fork with adjustable compression and rebound damping and 11.8-inch travel
Rear suspension: Kayaba single shock with adjustable preload, compression, and rebound damping, separate hi/lo speed compression adjuster and 12.4-inch travel
Brakes (f/r): 224mm floating disc/220mm disc
Tires (f/r): 80/100-21 51M Dunlop/110/90-19 62M Dunlop
LxWxH: 86.3x32.1x51.1
Seat height (in.): 38.8
Wheelbase (in.): 58.9
Ground clearance (in.): 14.6
Fuel capacity (gal.): 1.85
Dry weight (lb.): 220
Colors: Team Yamaha Blue/White; 50th Anniversary Yellow/Black
You gotta love the slew of engine mods on the YZ450F. The beauty is that most of these mods were integrated onto the 449cc engine that's stuffed into the YZF450 ATV. In addition, the YZF450's 11.4:1 compression engine (which is a lower compression ratio than the YZ450F engine) received a larger-capacity fan-cooled radiator so the powerplant will stay cool in even the most extreme riding conditions.
Yamaha engineers incorporated a number of other new-for-'06 changes to the YZF450, including a longer steering stem, new handlebars and a thicker seat-all designed to make the riding experience more pleasant. They also gave the YZF450 longer rear suspension travel to improve its ride and handling. They didn't forget about braking either, and they've fitted the YZF450 with a pair of potent dual-piston calipers up front and a dual-piston caliper in the rear.
Bottom line: Yamaha's lightest, most powerful ATV just got better.
Model: YZF450
MSRP: $6,999
Engine type: 449cc, liquid-cooled with fan, five-valve, DOHC, four-stroke with titanium valves
Bore x stroke (mm): 95 x 63.4
Compression ratio: 11.4:1
Carburetion: 39mm Keihin FCR flat-slide with throttle position sensor
Ignition: Digital CDI
Transmission: Five-speed manual clutch
Final drive: 2WD; sealed O-ring chain, cam style adjustment
Front suspension: Independent double wishbone, 9.1-inch travel with rebound and compression damping adjustment
Rear suspension: Cast-aluminum swing-arm, 10.6-inch travel with rebound and compression damping adjustment
Brakes (f/r): Dual hydraulic disc, twin piston/hydraulic disc, twin piston
Tires (f/r): AT21 x 7-10 radial/AT20 x 10-9 radial
LxWxH: 72.4x46.1x42.9
Seat height (in.): 31.9
Wheelbase (in.):50.4
Ground clearance (in.): 4.4
Fuel capacity (gal.): 2.6
Dry weight (lb.): 350
Colors: Team Yamaha Blue; White/Silver