The Tri-Z 250, produced from 1985 to 1986, stands as a legendary high-performance sport ATV, celebrated for its powerful 2-stroke, liquid-cooled, single-cylinder engine and advanced suspension systems. This model, known by its code YTZ250S, was the flagship in the sport ATV segment during its production years, offering enthusiasts a potent combination of agility, speed, and handling that made it a formidable competitor and a thrill to ride. Its engineering quality and reliability, characteristic of the powersports legacy, cemented its status as a significant machine in ATV history, earning accolades for its racing prowess and exhilarating performance. This comprehensive factory service manual provides detailed information essential for the maintenance, repair, and optimization of your Tri-Z 250. It covers all critical systems, including the engine, cooling, fuel, transmission, clutch, final drive, body, frame, steering, suspension, brakes, and electrical components, with specific attention to common issues and their solutions. The manual offers step-by-step repair instructions, disassembly and assembly procedures, diagnostic guidance, and precise technical specifications such as torque values and fluid requirements. Its scope is designed to empower owners and technicians alike, ensuring the longevity and peak performance of this iconic sport ATV through factory-accurate, illustrated instructions. 🏷️ Basic Information Identification Make: Yamaha Model: Tri-Z 250 Model Code: YTZ250S Year: 1985-1986 👋 Introduction Market Position Segment: High-performance sport ATV Target Audience: Enthusiasts seeking to maintain, repair, and optimize their Yamaha Tri-Z 250 Competitive Analysis Competitors: Honda TRX series, Suzuki QuadRacer LT series, Kawasaki Bayou series Key Features Manual Benefit: Empowers owners with the knowledge to perform all necessary service and repair, saving time and money on dealership visits. Accessibility: Instant download and permanent storage for continuous access across multiple devices. Content Quality: Factory-accurate information, including detailed diagrams and exploded views for precise component identification and assembly. 📋 Manual Details Coverage Areas Covered Models: Tri-Z 250, YTZ250S Covered Years: 1985, 1986 Page Count Estimated Page Count: Varies (typical factory service manuals for this era can range from 300-600 pages) Manual Type Type: Factory Service Manual / Repair Manual Language Language: English Format Format: Digital Download (PDF) 📖 Manual Coverage Systems Covered Engine: Complete engine overhaul, tuning, specifications, and troubleshooting Cooling System: Radiator, hoses, coolant specifications, pump operation Fuel System: Carburetor (Mikuni VM Series), fuel pump, fuel tank, fuel lines, jetting Transmission: Gearbox disassembly, inspection, repair, and specifications Clutching: Clutch operation, adjustment, disassembly, and components Final Drive: Chain and sprocket maintenance, inspection, and replacement Body And Frame: Frame inspection, body panel removal and installation, seating, plastics Steering And Suspension: Handlebar, steering stem, front forks (preload, compression, rebound damping), rear shock absorber, swingarm, linkage Brakes: Front and rear brake systems, hydraulic lines, master cylinders, calipers, pads, bleeding procedures Electrical: Ignition system, lighting, charging system (stator, rectifier), battery, switches, fuses Wiring Diagrams: Comprehensive electrical wiring schematics Procedures Included Maintenance: Routine maintenance, lubrication, adjustments, pre-ride inspections Troubleshooting: Diagnostic procedures for common problems and system failures Repair: Step-by-step repair instructions for all major components and systems Disassembly Assembly: Detailed procedures for component removal and reinstallation Specifications Data: Torque values, clearances, fluid capacities, measurements Technical Depth Depth: Comprehensive coverage suitable for both DIY enthusiasts and professional mechanics, covering everything from basic maintenance to full engine and transmission rebuilds. 📊 Manual Specifications File Format Format: PDF Searchability: Searchable text for quick access to information Print Quality Quality: Identical to original printed manuals, includes clear illustrations and diagrams Binding Type Type: N/A (Digital - printable pages) Paper Type Type: N/A (Digital - printable pages) ⚙️ Engine Specifications Primary Engine Type: 2-stroke, Liquid-Cooled, Reed Valve, Single Cylinder Displacement: 236 cc (14.4 cubic inches) Bore X Stroke: 66.0 mm x 68.0 mm (2.60 in x 2.68 in) Compression Ratio: 6.7:1 Performance Horsepower Estimated: Approximately 27-30 hp (stock) Torque Estimated: Not explicitly stated, but strong mid-range power delivery Fuel System Carburetor Model: Mikuni VM34SS Fuel Type: Unleaded gasoline (typically 91 octane or higher) Fuel Mix: Premix (typically 20:1 or 32:1 ratio of unleaded gasoline to 2-stroke oil, refer to manual for exact specification) 🔧 Transmission Standard Type: Constant Mesh, 6-speed Sequential Optional Type: N/A Features Clutch Type: Wet, multiple disc Transmission Oil Type: Yamaha Genuine Gear Oil or equivalent SAE 80 API GL-4 (refer to manual for specific viscosity and capacity) 📐 Dimensions Exterior Length: Approximately 73.4 inches (1865 mm) Width: Approximately 45.5 inches (1155 mm) Height: Approximately 43.5 inches (1105 mm) Weights Dry Weight: Approximately 397 lbs (180 kg) Fuel Tank Capacity: 2.4 US gal (9.0 L) 🛡️ Safety Features Ratings Crash Test Results: N/A (ATV category, not subject to automotive crash testing standards) Active Features Braking System: Dual front disc brakes, single rear disc brake Passive Features Handlebars: Wide handlebars for control and leverage 💡 Technology Features Infotainment System: N/A (Basic mechanical and electrical systems) Driver Assistance Features: N/A Connectivity Features: N/A 🔧 Maintenance Service Intervals Oil Change Transmission: Every 10-20 hours of...