2009 Yamaha YZ250
General Specifications
| Model | Yamaha YZ250 |
| Year | 2009 |
| Category | Motocross |
| Engine Type | Liquid-cooled 2-stroke single-cylinder, reed-valve induction with Yamaha Power Valve System (YPVS) |
| Weight | Approx. 103 kg wet/curb weight |
Engine
| Displacement | 249 cc |
| Bore x Stroke | 66.4 x 72.0 mm |
| Compression Ratio | 8.9-10.6:1 |
| Fuel System | Keihin PWK38S 38 mm carburettor with reed-valve induction | Replacement Options |
| Ignition | CDI magneto |
| Spark Plug | NGK BR8EG |
| Spark Plug Gap | 0.5-0.6 mm |
| Cooling System | Liquid cooled |
| Starting System | Kickstarter |
Transmission
| Transmission | 5-speed constant-mesh |
| Clutch | Wet multi-plate, coil spring |
| Final Drive | Chain, 14T/50T final gearing |
Dimensions
| Overall Length | 2,184 mm |
| Overall Width | 827 mm |
| Overall Height | 1,306 mm |
| Wheelbase | 1,481 mm |
| Ground Clearance | 381 mm |
| Seat Height | 993 mm |
| Fuel Capacity | 8.0 L |
Chassis
Suspension
| Front Suspension | 48 mm KYB Speed Sensitive System (SSS) inverted twin-chamber fork with adjustable compression and rebound damping | Fork Oil Levels |
| Front Suspension Travel | 300 mm |
| Rear Suspension | KYB link-type Monocross single shock with adjustable spring preload, rebound, low-speed compression and high-speed compression damping |
| Rear Suspension Travel | 315 mm |
| Fork Oil | Yamaha Suspension Oil S1; standard outer-chamber quantity approximately 350 cc per leg, adjustable approximately 300-375 cc; inner damper approximately 195-205 cc |
Brakes & Wheels
| Front Brake | Hydraulic single wave disc with twin-piston caliper |
| Rear Brake | Hydraulic single wave disc |
| Front Wheel Size | 21 x 1.60 in |
| Rear Wheel Size | 19 x 2.15 in |
Service Data
| Fuel Type | Premium unleaded petrol, 95 RON or higher |
| Premix Information | 30:1 petrol-to-2-stroke oil using Yamalube 2-R or equivalent high-quality racing 2-stroke oil | Premix Calculator |
| Gearbox Oil | Yamalube 4 SAE 10W-30 or equivalent motorcycle oil; approximately 0.75 L periodic oil change, 0.80 L total capacity |
| Air Filter | Washable oiled foam air-filter element |
| Service Notes | Competition 2-stroke with premix engine lubrication and separate transmission oil. Maintain the specified premix ratio, service the air filter frequently, inspect spark plug and piston condition regularly, and keep the YPVS power-valve system clean and correctly adjusted. |
2009 Yamaha YZ250: Yamaha Sticks With the Proven Two-Stroke
The 2009 Yamaha YZ250 was a minor-update model and remained substantially similar to the successful 2008 machine. By this stage Yamaha had already established the key ingredients of the modern YZ250: the aluminium semi-double-cradle frame introduced in 2005, KYB Speed Sensitive System suspension introduced in 2006, and the long-developed 249 cc reed-valve two-stroke engine.
The engine continued with Yamaha's YPVS power-valve system and a 38 mm Keihin PWK carburettor, delivering the broad and responsive powerband for which the YZ250 had become known. Owners maintaining the original induction system can use the MXOwners carburettor reference when checking repair or replacement options.
Suspension remained one of the bike's strongest features. The 48 mm KYB SSS fork and link-type Monocross rear shock provided a combination of compliance, bottoming resistance and adjustment that helped the YZ250 remain competitive even as four-strokes increasingly dominated motocross racing. The MXOwners fork oil reference is useful when servicing these twin-chamber forks.
Yamaha continued to specify a 30:1 premix ratio, while the five-speed gearbox retained its own separate oil supply. The MXOwners premix calculator can help owners mix fuel accurately.
Historically, the 2009 YZ250 is significant because Yamaha chose continuity while several rival Japanese manufacturers were abandoning 250 two-strokes. Rather than replacing the YZ250 with the YZ250F, Yamaha kept both models in production, allowing riders to choose between two-stroke simplicity and four-stroke technology.
