Target Audience:
Owners, novice mechanics, and experienced technicians seeking detailed repair and maintenance information for the Yamaha TTR90.
Vehicle Segment:
Entry-level youth dirt bike, often used for trail riding and recreational off-roading.
Competitors:
Honda CRF70F, Kawasaki KLX110 (slightly larger displacement), Suzuki DR-Z70 (later model).
Vehicle Purpose:
Designed for young riders transitioning to off-road riding, emphasizing ease of use, reliability, and manageable power delivery.
Manual Value Proposition:
Provides essential knowledge to maintain and repair the TTR90, saving on dealership costs and enabling enthusiasts to understand their vehicle intimately.
Engine:
Complete engine disassembly, assembly, diagnosis, tuning, and repair for all internal and external components.
Fuel System:
Carburetor assembly, adjustment, cleaning, fuel tank, fuel lines, and fuel pump (if applicable).
Ignition System:
CDI unit, spark plug, ignition coil, stator, and troubleshooting ignition problems.
Transmission:
Clutch operation, gear shifting mechanism, internal transmission components, lubrication, and adjustments.
Chassis And Suspension:
Front forks (assembly, oil changes, seals), rear shock absorber, swingarm, linkages, bearings, and alignment.
Brakes:
Front and rear brake systems, including brake levers, calipers, master cylinders, brake pads, brake fluid replacement, bleeding procedures, and drum brake adjustment (if applicable).
Electrical System:
Wiring diagrams, battery, charging system (alternator/stator), lighting (headlight, taillight, indicators), horn, starter system, and fuses.
Wheels And Tires:
Wheel removal and installation, spoke tensioning, tire mounting and dismounting, and recommended tire pressures.
Bodywork And Frame:
Fairings, plastics, seat, fuel tank removal and installation, frame inspections, and handlebar components.
Lubrication Points:
Identification of all lubrication points and recommended lubricants.
Basic Maintenance:
Oil changes, filter replacements, chain adjustment and lubrication, air filter cleaning/replacement, spark plug replacement, brake adjustments.
Troubleshooting:
Systematic diagnostic procedures for common problems related to starting, running, electrical issues, and braking.
Engine Repair:
Top-end rebuilds (piston, rings, cylinder), valve adjustments, gasket replacement, and crankshaft/connecting rod service.
Carburetor Rebuild:
Complete disassembly, cleaning, reassembly, and adjustment of the carburetor.
Suspension Service:
Front fork seal replacement, fork oil changes, and rear shock absorber servicing.
Brake Bleeding:
Step-by-step instructions for safely and effectively bleeding the brake system.
Electrical Diagnostics:
Using wiring diagrams to diagnose faults in the electrical system, including charging and ignition circuits.
Transmission Adjustment:
Clutch lever free play adjustment and internal transmission component checks.
Depth:
Comprehensive, covering everything from routine maintenance to complete engine and component overhauls. Suitable for home mechanics and professional technicians.
Diagnostic Charts:
Includes diagnostic flowcharts for identifying and resolving common issues.
Torque Specifications:
Detailed torque specifications for all critical fasteners and components.
Clearances And Tolerances:
Specific measurements for valve clearances, piston-to-cylinder wall, and other critical engine clearances.
Engine Type:
Four-stroke, SOHC, Air-cooled
Displacement:
88 cc (cubic centimeters)
Bore X Stroke:
50.0 mm x 45.2 mm (typical for this engine family)
Compression Ratio:
9.5:1 (typical)
Carburetor:
Mikuni VM17 (typical specification)
Ignition:
TCI (Transistor Controlled Ignition)
Horsepower:
Approximately 6-7 HP (estimated, actual figures may vary by region and tuning).
Torque:
Approximately 7-8 Nm (estimated).
Fuel Type:
Unleaded Gasoline
Fuel Tank Capacity:
Approximately 4.5 Liters (1.2 US gal)
Engine Oil Change:
Every 1000 km (600 miles) or 6 months, whichever comes first. More frequent changes recommended for heavy use.
Oil Filter Replacement:
At every oil change, or as specified in manual. (Note: TTR90 may have a simple screen filter or paper element, manual will specify).
Air Filter Cleaning:
Every 500 km (300 miles) or more frequently in dusty conditions.
Spark Plug Inspection:
Every 1000 km (600 miles) or annually.
Valve Clearance Check:
Every 4000 km (2500 miles).
Chain Adjustment Lubrication:
Every 500 km (300 miles) or after washing/wet riding.
Engine Oil Viscosity:
Yamalube 4 (10W-40) or equivalent API SE, SF, SG, SH, SJ, or higher.
Brake Fluid Type:
DOT 3 or DOT 4
Fork Oil Type:
Yamaha No. 10 (or equivalent 10W fork oil)
Carburetor Fouling:
Can be prone to gumming up if fuel sits for extended periods, requiring cleaning. Idle mixture adjustment can be sensitive.
Clutch Wear:
Automatic clutch plates can wear over time with aggressive use, leading to slipping. Regular checks and potential replacement of clutch springs/plates are part of long-term maintenance.
Electrical Connections:
As with many off-road vehicles, electrical connections can be susceptible to corrosion from dirt and moisture, requiring periodic inspection and dielectric grease application.
Suspension Seals:
Front fork seals can develop leaks with hard use, necessitating seal replacement.
