2008 Yamaha YZ450F
General Specifications
| Model | Yamaha YZ450F |
| Year | 2008 |
| Category | Motocross |
| Engine Type | Liquid-cooled, 4-stroke, DOHC, 5-valve single-cylinder |
| Weight | 99.5 kg dry |
Engine
| Displacement | 449 cc |
| Bore x Stroke | 95.0 x 63.4 mm |
| Compression Ratio | 12.3:1 |
| Fuel System | Keihin FCR-MX39 flat-slide carburettor with throttle position sensor | Replacement Options |
| Ignition | CDI magneto |
| Spark Plug | NGK CR8E |
| Spark Plug Gap | 0.7-0.8 mm (0.028-0.031 in) |
| Cooling System | Liquid cooled |
| Starting System | Kick starter with automatic decompression and hot-start system |
Transmission
| Transmission | 5-speed constant-mesh |
| Clutch | Wet multi-plate |
| Final Drive | Chain, 13-tooth front / 49-tooth rear sprocket, 3.769:1 secondary ratio |
Dimensions
| Overall Length | 2,192 mm |
| Overall Width | 825 mm |
| Overall Height | 1,305 mm |
| Wheelbase | 1,495 mm |
| Ground Clearance | 373 mm |
| Seat Height | 989 mm |
| Fuel Capacity | 7.0 L |
Chassis
Suspension
| Front Suspension | 48 mm KYB inverted Speed Sensitive System twin-chamber fork, adjustable compression and rebound damping | Fork Oil Levels |
| Front Suspension Travel | 300 mm (11.8 in) |
| Rear Suspension | Link-type Monocross with KYB gas/oil shock, titanium spring, adjustable preload, high-/low-speed compression and rebound damping |
| Rear Suspension Travel | 313 mm (12.3 in) rear wheel travel; shock absorber stroke 131.5 mm |
| Fork Oil | Yamaha Suspension Oil S1; total oil capacity 541 cc per fork |
Brakes & Wheels
| Front Brake | Hydraulic single disc, 250 mm |
| Rear Brake | Hydraulic single disc, 245 mm |
| Front Wheel Size | 21 x 1.60 in aluminium spoked wheel |
| Rear Wheel Size | 19 x 2.15 in aluminium spoked wheel |
Service Data
| Fuel Type | Premium unleaded petrol, minimum 95 RON |
| Premix Information | Not applicable - 4-stroke engine |
| Gearbox Oil | Engine and transmission share the same dry-sump engine oil supply; 0.95 L periodic oil change, 1.0 L with oil filter replacement, 1.2 L total capacity. API SG or higher, JASO MA motorcycle oil. |
| Air Filter | Wet-type foam element |
| Service Notes | Dry-sump lubrication. Maintain frequent oil and filter changes, inspect valve clearance regularly, keep the foam air filter clean and correctly oiled, and maintain correct FCR-MX39 jetting, accelerator-pump and hot-start operation. The 2008 model received revised intake porting, cam timing, frame rigidity, suspension settings and lighter front-end components. |
2008 Yamaha YZ450F: Refining the Aluminium-Frame Generation
The 2008 Yamaha YZ450F was an evolutionary development of the aluminium-framed generation introduced in 2006 rather than an all-new model. Yamaha concentrated on improving low-to-midrange response, front-end feel and suspension performance while retaining the proven 449 cc five-valve engine and five-speed transmission.
Engine changes included revised intake-port shapes and altered cam profiles, with intake valve timing and overlap adjusted to improve torque through the lower and middle rev range. The Keihin FCR-MX39 carburettor remained, and owners maintaining one can compare replacement and tuning options through the MXOwners carburettor reference. Yamaha also refined piston clearance and gear backlash to reduce mechanical noise.
Chassis development focused on steering response. The head-pipe and steering stem were shortened, frame rigidity was rebalanced around the pivot area, and lighter fork protectors, brake components, axle hardware and triple-clamp parts reduced weight at the front of the bike. These changes were intended to make the YZ450F easier to tip into corners while retaining stability.
The 48 mm KYB Speed Sensitive System fork received revised outer tubes, damping and internal settings, while the Monocross rear suspension gained altered linkage geometry and revised settings. Owners servicing the fork can check the MXOwners fork oil reference for additional information.
For current owners, the 2008 model represents a mature version of Yamaha's carburetted five-valve 450. Model-specific parts can be checked through the MXOwners Parts Finder, while the standard tyre sizes can be compared using the MXOwners Tyre Size Guide.
