Model Variant:
TZR125 (2-stroke, race-replica styling), DT125R (2-stroke, dual-sport)
Years Covered:
1987, 1988, 1989, 1990, 1991, 1992, 1993
Chassis Codes:
TZR125: 2RH, 3RP (varies by region/year); DT125R: 3BN, 4BL, 4ES (varies by region/year)
Engine Codes:
TZR125: 2RH; DT125R: 3BM (varies by region/year)
Positioning:
The Yamaha TZR125 and DT125R were popular entry-level to mid-level performance motorcycles in the late 1980s and early 1990s, appealing to riders seeking sporty performance (TZR) or versatile off-road/on-road capability (DT).
Competitors Tzr125:
Suzuki RG125 Gamma, Honda NSR125R, Aprilia AF1 125.
Competitors Dt125R:
Honda CR125 (later models), Suzuki RM125 (later models), Kawasaki KX125 (later models) - though DT leans more towards dual-sport/enduro.
Features:
Full fairing, sporty ergonomics, high-revving 2-stroke engine, race-inspired styling, capable chassis for its class.
Features:
Aggressive styling, capable off-road suspension, powerful 2-stroke engine with strong low-end torque, dual-purpose usability.
Value Proposition:
This manual is essential for owners and mechanics to maintain, diagnose, and repair these iconic Yamaha 125cc two-strokes, ensuring longevity and optimal performance.
Engine Mechanical:
Top-end overhaul, bottom-end assembly, cylinder and piston inspection, crankshaft, bearings, seals, timing, lubrication system.
Fuel System:
Carburetor (Mikuni VM24SS for TZR125, Mikuni VM24SH for DT125R) disassembly, cleaning, adjustment, jetting, fuel pump (if applicable), fuel lines.
Ignition System:
CDI unit, ignition coil, spark plug, stator, pickup coil, timing verification.
Cooling System:
Liquid cooling (TZR125), air cooling (DT125R): radiator, hoses, water pump, thermostat (if applicable), coolant specifications.
Exhaust System:
Expansion chamber (TZR125), silencer, mufflers, pipe sealing, carbon deposit cleaning.
Transmission:
Gearbox internal components, clutch assembly, clutch plates, pressure plate, clutch cable adjustment, oil specifications.
Electrical System:
Wiring diagrams, lighting, charging system (stator, rectifier/regulator), battery, starter motor (if applicable), switches, fuses.
Suspension:
Front forks (telescopic), rear mono-shock suspension (TZR125), twin rear shocks (DT125R), fork oil specifications, seal replacement, damper adjustments.
Brakes:
Front and rear disc brakes (hydraulic), brake caliper service, master cylinder overhaul, brake fluid specifications, pad replacement, bleeding procedures.
Wheels Tires:
Wheel bearing service, spoke tension (DT125R), tire pressure specifications, rim types.
Frame Bodywork:
Frame inspection, fairing removal and installation, seat, fuel tank, fenders, handlebars, controls.
Routine Maintenance:
Oil changes, spark plug replacement, air filter cleaning/replacement, chain adjustment and lubrication, brake adjustments.
Troubleshooting:
Diagnostic guides for common problems, symptom-based troubleshooting charts.
Engine Rebuild:
Complete engine disassembly, inspection, measurement, and reassembly procedures.
Carburetor Tuning:
Step-by-step instructions for cleaning, adjusting, and re-jetting the carburetor for optimal performance.
Electrical Diagnosis:
Testing of electrical components using multimeters, troubleshooting wiring issues.
Suspension Overhaul:
Fork seal replacement, shock absorber servicing, and tuning recommendations.
Brake System Maintenance:
Bleeding, fluid replacement, caliper and master cylinder servicing.
Depth:
Comprehensive: Covers everything from basic fluid checks and adjustments to full engine, transmission, and electrical system overhauls.
Diagnostic Capabilities:
Advanced diagnostic procedures for identifying and resolving complex mechanical and electrical faults.
Torque Specifications:
Detailed torque values for all critical fasteners.
Clearances Tolerances:
Specific measurements for critical component clearances and wear tolerances.
Engine Type:
Liquid-cooled (TZR125) / Air-cooled (DT125R), 2-stroke, single-cylinder
Displacement:
124 cc (approximate)
Bore X Stroke:
TZR125: 56.4 mm x 50.0 mm; DT125R: 56.5 mm x 50.6 mm (typical values, may vary by specific model code).
Compression Ratio:
TZR125: approx. 7.2:1; DT125R: approx. 7.1:1 (typical values, varies by region/year).
Horsepower:
TZR125: Approx. 25-30 HP (region dependent, often restricted for licensing); DT125R: Approx. 19-26 HP (region dependent).
Torque:
TZR125: Approx. 17-20 Nm; DT125R: Approx. 17-19 Nm (typical values).
Carburetor Type:
TZR125: Mikuni VM24SS; DT125R: Mikuni VM24SH (common fitments).
Fuel Type:
Unleaded gasoline (RON 91 or higher recommended)
Premix Ratio:
50:1 (Yamalube 2-stroke oil or equivalent) - manual will specify Yamaha's recommendation.
Ignition System:
Electronic ignition (CDI)
Lubrication Type:
Autolube (automatic oil injection system)
Starting System:
Kick starter
Overall Length:
TZR125: Approx. 1980 mm; DT125R: Approx. 2100 mm (varies by specific model).
Overall Width:
TZR125: Approx. 735 mm; DT125R: Approx. 805 mm (varies by specific model).
Overall Height:
TZR125: Approx. 1120 mm; DT125R: Approx. 1205 mm (varies by specific model).
Seat Height:
TZR125: Approx. 780 mm; DT125R: Approx. 855 mm (varies by specific model).
Wheelbase:
TZR125: Approx. 1340 mm; DT125R: Approx. 1385 mm (varies by specific model).
Ground Clearance:
TZR125: Approx. 140 mm; DT125R: Approx. 260 mm (varies by specific model).
Dry Weight:
TZR125: Approx. 130 kg; DT125R: Approx. 118 kg (varies by specific model).
Wet Weight:
TZR125: Approx. 142 kg; DT125R: Approx. 130 kg (estimated, with fluids).
Fuel Tank Capacity:
TZR125: 10 Liters; DT125R: 10 Liters (typical values, manual specifies exact capacity).
Oil Tank Capacity:
Approx. 1.5 Liters (Autolube system)
Safety Ratings:
N/A (Motorcycle safety ratings for this era were not standardized like modern vehicles).
Braking System:
Hydraulic front and rear disc brakes. Dual-piston caliper on front, single-piston on rear common.
Lighting:
Headlight, taillight, brake lights, turn signals.
Frame Construction:
Steel diamond frame (TZR125), steel cradle frame (DT125R) providing structural integrity.
Tire Specifications:
Tube-type tires common. Front: 90/90-17 (TZR), 90/90-21 (DT); Rear: 110/80-17 (TZR), 120/90-17 (DT) - typical sizes.
Oil Change Interval:
Every 3,000-5,000 km or annually (as per manual recommendation for transmission oil).
Spark Plug Replacement:
Every 4,000-6,000 km (manual will specify plug type and gap).
Air Filter Cleaning:
Every 2,000-3,000 km (or as needed depending on riding conditions).
Chain Maintenance:
Lubricate every 500-1000 km, adjust slack as needed (typically 20-30mm free play).
Brake Fluid Change:
Every 2 years or as recommended.
Engine Oil Type:
2-stroke pre-mix oil (e.g., Yamalube 2-stroke oil, Castrol TTS, Motul 710 2T)
Transmission Oil Grade:
SAE 80 API GL-4 (Yamaha Motorcycle Gear Oil specified)
Brake Fluid Type:
DOT 3 or DOT 4 hydraulic brake fluid (manual will specify exact type).
Coolant Type:
TZR125: Permanent type antifreeze coolant (50/50 mixture with distilled water). DT125R: Not applicable (air-cooled).
Common Issues:
Carburetor gumming/clogging due to infrequent use, exhaust power valve sticking (TZR125), ignition coil failure, stator output degradation, fork seal leaks, rear shock absorber wear, clutch wear.
Common Fixes:
Regular carburetor cleaning and fuel stabilization, power valve cleaning and lubrication, electrical component testing and replacement, suspension seal replacement, clutch plate replacement.
Yamaha Heritage:
Yamaha Motor Company, established in 1955, has a rich history in motorcycle manufacturing, particularly with its performance-oriented 2-stroke engines and innovative designs.
Tzr125 Evolution:
The TZR line was Yamaha's answer to the growing 125cc sportbike segment, offering a taste of GP racing technology to the masses. It evolved from earlier models and was later succeeded by different iterations.
Dt125R Evolution:
The DT series represents Yamaha's long-standing commitment to dual-sport and off-road motorcycles. The DT125R built upon the legacy of the original DT models, incorporating improved suspension and performance for its time.
Production Period:
1987-1993 for the specific generation covered by this manual. Subsequent models and variations continued in different markets.
Manufacturing Locations:
Primarily Japan, with potential assembly in other Yamaha global facilities.
