1978 Yamaha YZ400 Specifications and Specs
Specifications, manuals and workshop reference information.
Note: Specs are compiled from factory data, manuals and owner feedback. Bikes vary — if yours is different, jump into the forum and share it.
General Specifications
| Engine Type | Air-cooled, two-stroke, single cylinder |
| Displacement | 397 cc |
| Bore × Stroke | 85 × 70 mm |
| Compression Ratio | 8.2 : 1 |
| Maximum Power | Not specified |
| Maximum Torque | Not specified |
| Carburetor | Mikuni VM38 |
| Lubrication | Fuel premix |
| Fuel Mix Ratio | 20 : 1 |
| Ignition | CDI magneto |
| Spark Plug | NGK B9EV |
| Spark Plug Gap | 0.5 – 0.6 mm |
Transmission
| Transmission Type | 5-speed constant mesh |
| Clutch | Wet multi-plate |
| Primary Reduction | Not specified |
| Final Reduction | Not specified |
| Overall Reduction | Not specified |
Dimensions
| Overall Length | 2180 mm |
| Overall Width | 820 mm |
| Overall Height | 1230 mm |
| Wheelbase | 1480 mm |
| Ground Clearance | 300 mm |
| Fuel Tank Capacity | 9 L |
Chassis
| Frame Type | Single cradle steel frame |
| Caster Angle | Not specified |
| Trail | Not specified |
| Front Suspension | Telescopic fork |
| Rear Suspension | Swingarm with dual shock absorbers |
| Front Suspension Travel | Not specified |
| Rear Suspension Travel | Not specified |
Brakes & Wheels
| Front Tire | 3.00-21 |
| Rear Tire | 4.50-18 |
| Front Brake | Drum brake |
| Rear Brake | Drum brake |
400cc Other Specs
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