Market Niche:
Performance-oriented motocross competition machine.
Competitors 2005:
KTM 125 SX, Honda CR125R, Kawasaki KX125, Suzuki RM125.
Key Features Vehicle:
Lightweight chassis, potent two-stroke engine with YPVS (Yamaha Power Valve System), advanced suspension, and competitive pricing.
Key Features Manual:
Factory-backed information, detailed illustrations, and comprehensive troubleshooting guides ensure accurate repairs and optimal performance.
Systems Covered:
Engine, Transmission, Clutch, Cooling System, Fuel System, Ignition System, Electrical System, Suspension (Front & Rear), Brakes (Front & Rear), Frame, Bodywork, Wheels, Tires, Controls, Maintenance, Troubleshooting, Diagnostics, Specifications
Manual Type:
Factory Service Manual / Repair Manual
Format:
Digital Download (PDF)
Engine Management:
Complete engine disassembly, assembly, timing, and component specifications for the two-stroke power plant.
Drivetrain:
Detailed procedures for clutch operation, transmission overhaul, and gear shift mechanism.
Suspension And Steering:
Front fork (USD) and rear monoshock suspension maintenance, adjustment, and rebuild. Steering head bearing service.
Brakes:
Hydraulic front disc and rear disc brake system maintenance, bleeding, pad replacement, and caliper service.
Electrical System:
Ignition system components, CDI unit, lighting circuits (if applicable), and troubleshooting of electrical issues.
Fuel And Exhaust:
Carburetor tuning and rebuilding, fuel tank maintenance, and exhaust system service.
Maintenance:
Scheduled maintenance tasks, fluid changes, filter replacements, chain adjustment, and general upkeep.
Troubleshooting:
Systematic diagnostic procedures for common and uncommon performance issues, starting problems, and system failures.
Repair And Rebuild:
Complete tear-down and reassembly instructions for major vehicle components, including engine and transmission.
Technical Specifications:
Detailed torque specifications for all fasteners, fluid capacities, engine timings, and dimensional data.
Depth Of Coverage:
Comprehensive, covering everything from basic adjustments to complete engine and transmission overhauls. Suitable for both novice mechanics and experienced technicians.
Engine Type:
Liquid-cooled, 2-stroke, Reed valve, YPVS
Displacement:
124 cc (7.58 cu. in.)
Bore X Stroke:
54.0 mm x 54.5 mm (2.13 in x 2.15 in)
Compression Ratio:
8.2:1 (approximate, varies with altitude and fuel)
Horsepower:
Estimated 38-40 HP at peak RPM (specific figures not provided in product description, but typical for class)
Torque:
Estimated 20-22 lb-ft (specific figures not provided in product description, but typical for class)
Carburetor:
Keihin PWK38S, Flat slide
Fuel Type:
Unleaded gasoline, minimum 91 octane (AKI)
Fuel Mixture:
2-stroke oil/gasoline mix (refer to manual for precise ratio, typically 32:1 or 40:1)
Lubrication System:
Pre-mix in fuel, transmission oil
Safety Ratings:
Not applicable in the traditional automotive sense. Focus is on rider safety through proper maintenance and operation.
Active Safety:
Responsive braking system, predictable handling, strong engine braking.
Passive Safety:
Robust frame construction, protective bodywork.
Infotainment Systems:
N/A - Competition motocross bike, no infotainment features.
Driver Assistance:
N/A - Competition motocross bike, no driver assistance features.
Connectivity:
N/A - Competition motocross bike, no connectivity features.
Ypvs System:
Yamaha Power Valve System (YPVS) adjusts exhaust port timing for broader powerband and improved low-to-mid range performance.
Suspension Technology:
Kayaba (KYB) Speed Sensitive System (SSS) forks and a KYB rear shock absorber (specifics vary but were advanced for the era).
Oil Change Interval Transmission:
Refer to manual for specific mileage/hour intervals, typically every 10-15 hours of riding.
Air Filter Cleaning:
Regular cleaning recommended, frequency depends on riding conditions (e.g., every few rides).
Spark Plug Replacement:
Refer to manual; typically checked and cleaned at regular intervals, replaced as needed.
Transmission Oil Type:
Yamalube Gear Oil 10W-30 or equivalent API GL-4, SAE 80 (refer to manual for exact specification).
Coolant Type:
Permanent antifreeze (ethylene glycol based) with distilled water, 50/50 mixture.
Brake Fluid Type:
DOT 3 or DOT 4 hydraulic brake fluid (refer to manual for specific requirement).
Common Wear Items:
Clutch plates, piston rings, spark plug, air filter, chain and sprockets, wheel bearings, suspension seals.
Potential Problems 2005 Yz125:
As with any high-performance two-stroke, proper jetting is crucial to prevent overheating or plug fouling. Suspension seals can be prone to leaks if not maintained. Crankshaft seals can degrade over time.
Brand Focus:
Yamaha has a long and successful history in motorcycle racing, particularly in motocross and off-road disciplines.
Yz Series Heritage:
The YZ series has been a cornerstone of Yamaha's motocross lineup for decades, consistently evolving with technological advancements.
Yz125 Evolution 2005:
The 2005 model continued the refinement of the YZ125, building on previous generations with chassis improvements, engine tuning, and suspension advancements.
Manufacturing Location:
Japan (typical for Yamaha motorcycles)
Motorcycle Awards:
While specific awards for the 2005 model are not detailed in the product description, the YZ125 consistently received praise in motorcycle media for its performance and handling within its class.
Media Reviews 2005:
Typically reviewed favorably for its nimble handling, strong engine for its displacement, and competitive chassis. Often highlighted as a top choice for 125cc class racing.
