The 2009 Yamaha YZ85 is a 2-stroke motocross bike powered by a liquid-cooled, single-cylinder, reed-valve engine. Here’s a more detailed breakdown of the powertrain and performance specs:
Engine Specifications:
- Engine Type: 84cc, single-cylinder, 2-stroke, reed-valve
- Bore x Stroke: 47.0 mm x 47.8 mm
- Compression Ratio: 8.6:1
- Fuel System: 28mm Keihin carburetor
- Ignition System: CDI (Capacitor Discharge Ignition)
- Lubrication: Pre-mixed fuel and oil (2-stroke oil)
Performance:
- Horsepower: Approximately 19 hp at peak RPM (around 11,000 RPM)
- Torque: Around 10.5 Nm (7.7 lb-ft) at peak RPM (rough estimate)
- Redline: Approximately 11,500 RPM (variable depending on mods)
Power Delivery:
The YZ85 is designed to have a strong mid-range powerband, ideal for riders looking to develop their skills in competitive motocross. The engine delivers a smooth and linear power delivery, which makes it easier for younger or less experienced riders to control. The 2-stroke engine provides quick throttle response, and the powerband is more top-end oriented, but it has decent torque in the mid-range as well, making it versatile for various track conditions.
Weight and Handling:
- Dry Weight: 157 pounds (71 kg)
- Suspension: Front: 36mm KYB inverted fork, Rear: KYB monoshock
- Seat Height: 33.1 inches (841 mm)
Top Speed:
- The top speed of the 2009 YZ85 is around 65-70 mph (105-113 km/h), depending on factors like rider weight and modifications.
This combination of a high-revving 2-stroke engine and lightweight chassis makes the 2009 YZ85 an excellent choice for aspiring motocross racers, with enough power to be competitive in the 85cc class, while still being manageable for young riders.