Category:
Entry-level to intermediate motocross competition
Target Audience:
Young riders, aspiring motocross competitors, and hobbyists.
Key Competitors:
Honda CR80, Suzuki RM80, Kawasaki KX80
Motocross Performance:
Designed for off-road racing, known for nimble handling and responsive power delivery.
Durability:
Yamaha's reputation for robust two-stroke engine construction.
Engine:
Complete disassembly, inspection, assembly, tuning, and troubleshooting of the 78cc two-stroke engine.
Transmission:
Gearbox disassembly, inspection, assembly, clutch service, and shift mechanism.
Suspension:
Front fork (telescopic) and rear monoshock suspension service, including oil changes, seal replacement, and damper adjustments.
Brakes:
Front and rear drum brake system service, including lining inspection, adjustment, and cable maintenance.
Electrical System:
Ignition system troubleshooting, CDI unit, spark plug, lighting (if applicable), and wiring diagrams.
Fuel System:
Carburetor (Mikuni VM24SS) disassembly, cleaning, adjustment, jetting recommendations, and fuel tank/petcock service.
Cooling System:
Air-cooled engine maintenance.
Exhaust System:
Exhaust pipe and silencer inspection and maintenance.
Frame And Bodywork:
Frame inspection, seat, fenders, handlebars, and controls.
Routine Maintenance:
Oil changes, chain lubrication and adjustment, air filter cleaning/replacement, spark plug replacement, brake adjustment.
Troubleshooting:
Systematic diagnostic procedures for common problems such as starting issues, poor running, and electrical faults.
Engine Rebuild:
Detailed instructions for piston, ring, cylinder, crankshaft, and bearing replacement.
Carburetor Tuning:
Jetting recommendations for various conditions, idle speed adjustment, and throttle response optimization.
Suspension Service:
Front fork seal replacement, fork oil level and viscosity, rear shock absorber spring preload and damping adjustments.
Clutch Adjustment:
Cable free play adjustment and clutch plate inspection/replacement.
Wheel Service:
Tire inspection and replacement, spoke tensioning.
Depth:
Comprehensive, covering routine maintenance to complete engine and transmission rebuilds. Includes detailed torque specifications and diagnostic procedures.
Format:
PDF (Portable Document Format)
Searchability:
Typically text-searchable, allowing quick access to specific information.
Quality:
High-resolution scans of original documentation, ensuring clarity of text and diagrams.
Binding:
Not Applicable (Digital Download)
Paper:
Not Applicable (Digital Download)
Type:
Two-stroke, single-cylinder, reed valve induction
Displacement:
78 cc (4.76 cu. in.)
Bore X Stroke:
48.0 x 42.0 mm (1.89 x 1.65 in.)
Compression Ratio:
7.4:1 (Nominal)
Cooling System:
Air-cooled
Ignition System:
CDI (Capacitor Discharge Ignition)
Lubrication:
Pre-mix fuel/oil (Ratio typically 20:1 or 32:1, check manual for specific)
Horsepower:
Approx. 15-17 HP (Estimates vary)
Torque:
Not typically published for this class, but strong mid-range power.
Carburetor Model:
Mikuni VM24SS
Carburetor Type:
Single Barrel, Constant Velocity
Fuel Type:
Unleaded gasoline with appropriate two-stroke oil mixture
Overall Length:
Approx. 1825 mm (71.9 in.)
Overall Width:
Approx. 765 mm (30.1 in.)
Overall Height:
Approx. 1105 mm (43.5 in.)
Seat Height:
Approx. 770 mm (30.3 in.)
Wheelbase:
Approx. 1260 mm (49.6 in.)
Dry Weight:
Approx. 71 kg (157 lbs.)
Fuel Tank Capacity:
Approx. 5.5 L (1.45 US gal.)
Classification:
Competition Motorcycle (Not street legal)
Braking System:
Front and Rear Drum Brakes, designed for motocross use.
Chassis Design:
Robust steel frame providing stability and impact resistance.
Suspension Travel:
Generous suspension travel to absorb impacts and maintain control over rough terrain.
Oil Change Engine:
Refer to manual for specific interval, typically after a certain number of operating hours or competitive events.
Air Filter Cleaning:
Frequent cleaning/replacement recommended, especially in dusty conditions (e.g., every few rides).
Spark Plug Replacement:
Check and clean regularly, replace as needed based on performance (refer to manual for type and gap).
Chain Lubrication:
After every wash or ride in wet/muddy conditions.
Chain Adjustment:
Check for slack regularly (refer to manual for specification).
Transmission Oil:
Yamalube 10W-30 or equivalent API GL-4 gear oil.
Fork Oil:
Yamaha Fork Oil G10 or equivalent SAE 10W fork oil (Check manual for specific type and volume).
Coolant:
Not applicable (Air-cooled engine).
Brake Fluid:
Not applicable (Drum brakes use mechanical linkage, not hydraulic fluid).
Carburetor Fouling:
Common in older two-strokes due to fuel and oil mixtures, requiring regular cleaning and adjustment.
Clutch Wear:
Clutch plates can wear over time with aggressive riding, requiring replacement.
Suspension Seals:
Fork and shock seals can degrade, leading to oil leaks and reduced damping performance.
Engine Seals:
Crankshaft seals can fail, leading to air leaks and poor engine running.
Yamaha Legacy:
Yamaha has a long and distinguished history in motorcycle manufacturing, particularly in off-road and motocross racing.
Yz Series Lineage:
The YZ 80 was part of Yamaha's highly successful YZ line, which has consistently evolved to meet the demands of competitive motocross.
Production Period:
The YZ 80 was produced for many years, with significant updates throughout its lifecycle. The 1986 model represents a specific iteration within this lineage.
