Yamaha, the Japanese motorcycle manufacturer, introduced the original YZ motocross bikes in the 1970s. In fact, Yamaha created the very first single-shock production motocross bike. The line was expanded, altered, and revised substantially over the years. The YZ 85 was in production from 2000 to 2008; the 2007 model was a carryover. The YZ 125 was introduced in 1974; it was revised in 2005, and that model was carried over in 2007. The 250 was also introduced in 1974; it was revised in 2006. The 250F was released in 2001 and produced until 2008; it was revised in 2006 and carried over for 2007. The YZ 450F was made between 2003 and 2008.
All five models are powered by four-stroke, air-cooled, single-cylinder, carbureted engines. The numbers tell you how powerful each engine is: the 85's engine displaces 84 ccs, the 125 displaces 124 ccs, the 250 and 250F displace 244ccs, and the 450's displacement is 449 ccs. Three models have reed valve setups; the 250F and 450F have dual overhead cams and Yamaha's famous five-valve configuration. Disc brakes front and back provide stopping power. All models' front suspension is supplied by inverted forks with rebound damping; the rear suspension is twin-sided swing with an adjustable spring preload and rebound damping. All have kick starters. The YZ 85 and 125 have six-speed transmissions; the other three models have five-speed manual trannies.
Riders could choose to customize their bikes with a wide array of accessories, including switching out the clutch lever and adding fork guards. All models competed successfully in motocross throughout the years in which they were produced.
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- Model: YZ 85, YZ 125, YZ 250, YZ 250F, YZ 450F
- Engine Type: 84cc (YZ 85); 124cc (YZ 125); 249cc (YZ 250 & 250F); 450cc (YZ 450F), liquid-cooled single cylinder
- Bore and Stroke: 1.87 inches x 1.89 inches (YZ 85); 2.13 inches x 2.15 inches (YZ 125); 2.62 inches x 2.84 inches (YZ 250); 3.03 inches x 2.1 inches (YZ 250F); 3.74 inches x 2.5 inches (YZ 450F)
- Compression ratio: 8:2:1 (YZ 85); 8:6:1 (YZ 125);
- Valve Train: Reed valve (YZ 85, 125 & 250); DOHC (YZ 250F & 450F)
- Induction: Carburetor
- Ignition: Kick (YZ 85);
- Transmission: Six-speed manual (YZ 85 & 125; five-speed manual (YZ 250, 250F & 450F)
- Final Drive: Chain
- Fuel Capacity: 1.3 gallons (YZ 85); 2.1 gallons (YZ 125, 250 & 250F); 1.8 gallons (YZ 450F)
- Estimated Fuel Economy: N/A
- Brakes (Front): 7.8-inch disc (YZ 85); 9.9-inch disc (YZ 125, 250 & 3450); 9.8-inch disc (YZ 250F)
- Brakes (Rear): 5.8-inch disc (YZ 85); 9.7-inch disc (YZ 125, 250, 250F & 450F)
- Suspension (Front): Inverted fork with adjustable rebound damping
- Suspension (Rear): Twin-sided swing arm with adjustable spring preload shock and rebound damping
- Wheelbase: 49.5 inches (YZ 85); 56.8 inches (YZ 125); 58.3 inches (YZ 225); 57.8 inches (250F); 58.8 inches (YZ 450F)
- Rake: N/A
- Trail: N/A
- Seat Height: 31.9 inches
- Curb Weight: 146 pounds (YZ 85); 190 pounds (YZ 125); 211.6 pounds (YZ 250); 204 pounds (YZ 250F); 220 pounds (YZ 400)
- Tires (Front): 70/100 R17 (YZ 85); 80/100 R21 (YZ 125, 250, 250F & 450F);
- Tires (Rear): Dunlop 90/100 R14 (YZ 85); 100/90 R19 (YZ 125, 250, 250F & 450F)
- Aluminum Hot Start Lever
- Carbon Fiber Upper Fork Guards
- GYT-R Pivoting Clutch Lever
- Rear Brake Master Cylinder Guard
- Titanium Foot Pegs
- GYT-R Mini Cross Bar Pad Various Styles
- GYT-R Billet Clutch Lever With Roller Bearing
- GYT-R Factory Clutch Perch Assembly With Hot Start
- Yamaha Factory Racing Clamp Cover Various Styles
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