Model Variants:
XS400 Standard, XS400 Special (potential variations across years)
Production Years Covered:
1977, 1978, 1979, 1980, 1981, 1982
Target Audience:
Professional motorcycle technicians, experienced DIY enthusiasts, and owners seeking in-depth maintenance and repair knowledge for their Yamaha XS400.
Value Proposition:
Provides comprehensive, manufacturer-approved repair data, saving owners significant costs associated with dealership labor. Offers detailed, step-by-step instructions for complex tasks.
Benefits:
Empowers owners to perform their own maintenance and repairs, extends the lifespan of the motorcycle, enhances understanding of vehicle systems, facilitates accurate diagnostics.
Manual Source:
Original manufacturer's workshop manual, providing the most accurate and complete information.
Engine And Drivetrain:
Engine overhaul, tuning, carburetor service, ignition system, transmission maintenance and repair, clutch operation, final drive.
Chassis And Suspension:
Front fork service and rebuild, rear shock absorber inspection and replacement, steering head bearing maintenance, wheel bearing service.
Electrical System:
Complete wiring diagrams, lighting system troubleshooting, charging system (alternator, regulator/rectifier), starting system, battery maintenance.
Braking System:
Front and rear brake inspection, adjustment, hydraulic system service (master cylinder, calipers, lines), brake pad replacement.
Fuel System:
Fuel tank inspection, fuel pump operation (if applicable), fuel lines, carburetor cleaning, adjustment, and synchronization.
Bodywork And Trim:
Seat removal, fender inspection, headlight and taillight assembly, minor bodywork repair guidance.
Cooling System:
Air cooling system inspection and maintenance.
Exhaust System:
Exhaust pipe and muffler inspection, gasket replacement.
Routine Maintenance:
Oil change intervals and specifications, spark plug replacement, air filter cleaning/replacement, chain adjustment and lubrication, brake fluid checks, tire pressure.
Troubleshooting Guides:
Diagnostic charts for common starting, running, and electrical issues; symptom-based problem resolution.
Major Repairs:
Engine rebuild procedures, transmission disassembly and assembly, suspension component overhauls, carburetor rebuilding.
Technical Specifications:
Detailed torque specifications, engine clearances, valve adjustments, ignition timing settings, carburetor jetting data.
Tuning And Adjustment:
Engine tuning, idle speed adjustment, ignition timing adjustment, carburetor synchronization.
Diagnostic Charts:
Troubleshooting flowcharts for electrical and mechanical issues.
Depth:
Full factory-level technical depth, suitable for professional technicians and experienced DIY mechanics. Covers everything from basic adjustments to complete engine and transmission overhauls.
Engine Type:
Air-cooled, 4-stroke, DOHC parallel-twin
Displacement:
Approximately 392cc to 425cc (depending on specific model year variant and potential engine updates)
Bore X Stroke:
Typical figures around 69.0mm x 52.4mm (verify specific year in manual)
Compression Ratio:
Generally around 9.5:1 to 10.0:1 (verify specific year)
Horsepower Output:
Estimated 27-36 HP at 7,500-8,500 RPM (varies by year and tuning)
Torque Output:
Estimated 24-30 lb-ft at 6,000-7,000 RPM (varies by year)
Carburetion:
Twin Mikuni carburetors (e.g., VM30SC or similar size, depending on year)
Fuel Delivery:
Gravity feed from fuel tank, often with a vacuum-operated petcock.
Transmission Type:
Constant mesh 5-speed sequential gearbox
Transmission Variants:
No known optional transmissions for this model.
Clutch Type:
Wet, multiple-disc, cable-actuated clutch
Final Drive:
O-ring sealed chain drive
Overall Length:
Refer to specific model year specifications in manual (typically around 80-85 inches)
Overall Width:
Refer to specific model year specifications in manual (typically around 30-33 inches)
Wheelbase:
Refer to specific model year specifications in manual (typically around 55-57 inches)
Dry Weight:
Approximately 370-410 lbs (depending on year and configuration)
Fuel Capacity:
Typically 3.4 - 4.2 gallons (refer to manual for precise capacity)
Safety Features Notes:
As a vintage motorcycle, specific crash ratings are not applicable in the modern sense. Focus is on mechanical safety and rider control.
Braking System Type:
Disc front, Drum rear (early models) or Disc front, Disc rear (later models, especially Special variants).
Suspension System:
Telescopic front fork, Dual rear shock absorbers.
Lighting:
Headlight, taillight, brake lights, turn signals.
Oil Change:
Every 3,000-5,000 km or 6 months, whichever comes first (refer to manual for exact mileage).
Valve Adjustment:
Every 6,000-10,000 km (critical for engine health, refer to manual for precise interval and procedure).
Spark Plug Replacement:
Every 10,000-15,000 km or as per manual's recommendation.
Engine Oil Type:
Yamaha recommends API SE or SF service classification, SAE 20W-40 or 10W-30, or 20W-50 depending on ambient temperature. Always consult the manual.
Engine Oil Capacity:
Approx. 2.2 - 2.5 Liters with oil filter change (verify in manual).
Brake Fluid:
DOT 3 or DOT 4 Brake Fluid (check for specific recommendations in manual).
Fork Oil:
Yamaha Fork Oil G10 or equivalent SAE 10W fork oil. Capacity per fork leg will be specified.
Common Wear Points:
Carburetor synchronization and jet clogging due to age, cam chain wear and noise, fork seal leaks, rear shock absorber degradation, charging system issues (rectifier/regulator failures).
Typical Repairs:
Carburetor rebuild, valve adjustments, oil seal replacements, electrical connection cleaning and repair, chain and sprockets replacement.
Yamaha Legacy:
Yamaha Motor Company, a division of Yamaha Corporation, has a long history of producing high-quality motorcycles known for their performance, reliability, and innovation.
Xs400 Development:
The XS400 was introduced as part of Yamaha's 'XS' line of motorcycles, which featured parallel-twin engines. It aimed to compete in the middleweight segment, offering a balance of performance and manageability.
Year Specific Changes:
Significant changes occurred between the early 70s XS models and the late 70s/early 80s XS400. Later models saw updates like electronic ignition, improved braking (dual front discs on some), and styling variations (e.g., the 'Special' model with spoke wheels and different handlebars).
Manufacturing Location:
Primarily Japan.
