Segment:
Motocross/Off-road performance motorcycle.
Competitors:
KTM 125 EXC, Honda CR125R, Suzuki RM125, Kawasaki KX125 of the same era.
Engine Type:
Liquid-cooled, 2-stroke, single-cylinder.
Suspension Design:
Advanced Kayaba (KYB) suspension, often with adjustable components.
Performance Focus:
High-revving engine, lightweight chassis, designed for aggressive riding.
Engine:
Complete engine overhaul, disassembly, assembly, tuning, carburetor, cooling system, exhaust system.
Transmission:
Gearbox inspection, repair, clutch operation, maintenance.
Chassis:
Frame inspection, suspension (front fork, rear shock absorber), steering system, swingarm.
Brakes:
Front and rear brake system maintenance, hydraulic system bleeding, caliper and master cylinder service.
Electrical:
Ignition system, lighting, wiring diagrams, troubleshooting electrical faults.
Fuel System:
Fuel tank, fuel lines, carburetor tuning and maintenance.
Cooling System:
Radiator, coolant, water pump maintenance.
Exhaust System:
Exhaust pipe, silencer inspection and maintenance.
Maintenance:
Scheduled maintenance tasks, lubrication points, filter replacement, chain adjustment.
Troubleshooting:
Diagnostic flowcharts for common problems, fault finding guides.
Repair:
Detailed step-by-step repair procedures for all major components.
Disassembly Assembly:
Complete breakdown and reassembly instructions for engine, transmission, and chassis components.
Tuning:
Carburetor jetting, ignition timing, suspension setup guidance.
Depth:
Comprehensive, covering routine maintenance to full engine rebuilds and advanced diagnostics.
Engine Type:
2-stroke, single-cylinder, reed valve induction, liquid-cooled.
Displacement:
124 cc (7.57 cu in)
Bore X Stroke:
54.0 mm x 54.5 mm (2.13 in x 2.15 in)
Compression Ratio:
8.1:1 (approx.)
Horsepower:
Approximately 35-40 HP (actual figures vary, but this is typical for class)
Torque:
Approximate peak torque around 20-22 Nm (15-16 lb-ft)
Carburetor:
Keihin PWK38 (38mm) flat slide carburetor.
Fuel Type:
Unleaded gasoline, minimum 91 octane (RON+MON)/2).
Ignition System:
CDI (Capacitor Discharge Ignition).
Lubrication System:
Premix (2-stroke oil mixed with gasoline).
Transmission Type:
Constant-mesh 6-speed sequential.
Clutch:
Wet, multi-plate, cable-actuated.
Gear Ratios:
Specific gear ratios are detailed within the manual, critical for performance tuning.
Final Drive:
Chain drive (520 pitch is common).
Length:
Approximately 2,165 mm (85.2 in)
Width:
Approximately 810 mm (31.9 in)
Height:
Approximately 1,245 mm (49.0 in)
Wheelbase:
Approximately 1,435 mm (56.5 in)
Dry Weight:
Approximately 90 kg (198.4 lbs)
Wet Weight:
Approximately 97 kg (213.8 lbs) (with fluids)
Ground Clearance:
Approximately 335 mm (13.2 in)
Seat Height:
Approximately 970 mm (38.2 in)
Fuel Capacity:
Approximately 8.0 liters (2.1 US gal)
Oil Change:
Transmission oil change recommended every 10-15 hours of riding. Engine oil is premixed.
Air Filter Cleaning:
Frequent cleaning required (every few hours of riding depending on conditions).
Spark Plug Replacement:
Recommended every 20-30 hours of riding.
Piston Ring Replacement:
Recommended every 30-50 hours of riding for optimal performance.
Top End Rebuild:
Piston and cylinder inspection/rebuild typically every 50-100 hours, depending on usage and maintenance.
Transmission Oil:
Yamalube 2-stroke transmission oil or equivalent API GL-4 SAE 10W-30, 10W-40, or 20W-40 (check manual for exact specification).
Coolant:
Permanent type antifreeze coolant (ethylene glycol based) mixed with distilled water at a 50:50 ratio.
2 Stroke Oil:
High-quality synthetic 2-stroke racing oil specifically designed for premix applications.
Clutch Wear:
Clutch plates can wear over time, requiring replacement. Proper adjustment is key.
Carburetor Tuning:
Carburetor jetting can be sensitive to altitude and temperature, requiring occasional adjustment.
Suspension Seals:
Front fork and rear shock seals can degrade over time, leading to leaks.
Exhaust Port Fouling:
2-stroke engines can experience carbon buildup in the exhaust port, requiring cleaning.
Yamaha Legacy:
Yamaha has a long and storied history in motocross, with the YZ line being a cornerstone of their racing success.
Yz125 Development:
The 2000 model represents an evolution of Yamaha's successful YZ125 platform, incorporating refinements for improved performance and handling.
Key Changes 2000:
Specific chassis updates, suspension valving changes, and engine tuning for the 2000 model year.
Manufacturing Location:
Typically manufactured in Japan.
