Positioning:
The Kawasaki KX series of the early 1990s was a dominant force in motocross racing, known for its potent 2-stroke power and agile handling. This manual caters to owners and mechanics looking to maintain, repair, and optimize these competitive machines.
Competitors:
This manual is essential for owners of the 1990-1991 Kawasaki KX125 and KX250, directly competing with Yamaha YZ125/YZ250, Honda CR125R/CR250R, and Suzuki RM125/RM250 models of the same era.
Features:
Instant digital access, comprehensive coverage of all major systems, detailed troubleshooting guides, and lifetime protection policy for lost or damaged files.
Engine:
Comprehensive coverage of the 2-stroke engine, including top-end and bottom-end components, power valves, carburetor tuning, and cooling system.
Transmission:
Detailed instructions for the 6-speed transmission, including gear inspection, shift drum and forks, clutch operation, and gearbox lubrication.
Fuel System:
In-depth coverage of the fuel tank, fuel lines, fuel petcock, and carburetor (likely Keihin or Mikuni), including jetting specifications and adjustments.
Lubrication Cooling:
Information on the oil injection system (if applicable for the year/model), gearbox oil, and engine cooling system (liquid-cooled design).
Electrical System:
Wiring diagrams, ignition system (CDI, spark plug specifications), lighting, and basic electrical troubleshooting.
Suspension:
Front fork (likely Kayaba or Showa with adjustable compression and rebound) and rear shock absorber (likely with adjustable preload, compression, and rebound) maintenance, service, and tuning.
Steering System:
Steering head bearing maintenance and adjustment.
Bodywork Frame:
Fairing removal and installation, seat, fuel tank, and frame inspection.
Brakes:
Front and rear disc brake systems, including caliper maintenance, brake pad replacement, hydraulic system bleeding, and lever/pedal adjustments.
Wheels Tires:
Wheel bearing maintenance, spoke tensioning, tire selection and inflation pressure recommendations.
Intake Exhaust:
Airbox and filter maintenance, exhaust system inspection and service, power valve cleaning and operation.
Routine Maintenance:
Oil changes, filter cleaning/replacement, chain adjustment, spark plug inspection, general bolt checks.
Engine Overhaul:
Complete engine disassembly, inspection of internal components (piston, rings, cylinder bore, crankshaft, bearings), reassembly, and torque specifications.
Transmission Service:
Removal and installation of transmission components, gear meshing checks, and clutch adjustments.
Carburetor Tuning:
Detailed instructions for disassembling, cleaning, and re-jetting the carburetor for various conditions and modifications.
Suspension Servicing:
Fork oil changes, seal replacement, shock absorber servicing, and suspension adjustment techniques.
Electrical Troubleshooting:
Diagnostic procedures for common electrical issues using wiring diagrams.
Frame And Chassis Repair:
Inspection of frame integrity, steering head bearing replacement, and swingarm bearing service.
Depth:
Comprehensive, covering everything from basic owner maintenance to full engine rebuilds and advanced troubleshooting. Suitable for both novice mechanics and experienced technicians.
Type:
Liquid-cooled, 2-stroke, single-cylinder
Kx125 Bore X Stroke:
56.0 x 49.2 mm (approximate, may vary slightly)
Kx250 Bore X Stroke:
66.0 x 72.0 mm (approximate, may vary slightly)
Kx125 Displacement:
124 cc (approximate)
Kx250 Displacement:
249 cc (approximate)
Power Valves:
KIPS (Kawasaki Integrated Power-valve System) for improved low-end and mid-range power delivery.
Horsepower Kx125:
Estimated 35-40 HP (at crank, stock)
Horsepower Kx250:
Estimated 45-50 HP (at crank, stock)
Carburetor Kx125:
Keihin PWK35 or similar
Carburetor Kx250:
Keihin PWK37 or similar
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Oil Mixture:
Typically 32:1 or 40:1 pre-mix ratio or separate oil injection system, depending on specific sub-model and regional configuration.
Gearbox Oil Type:
SAE 80 or 90 GL-4 hypoid gear oil. Specific part numbers often available in the manual (e.g., Kawasaki Genuine Gear Oil).
Coolant Type:
Mixture of distilled water and ethylene glycol-based antifreeze (typically 50/50).
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions. Specific cleaning and oiling procedure detailed in manual.
Spark Plug Inspection:
Regularly, and replacement based on condition and plug type. Manual will specify correct plug and gap.
Chain Lubrication Adjustment:
Before every ride, and adjust tension as needed according to manual specifications.
Gearbox Oil Change:
Every 10-20 hours of operation, or as specified by Kawasaki. Manual will list capacity.
Suspension Service:
Fork oil changes typically every 20-30 hours, full suspension service annually or as needed.
Engine Top End Rebuild:
Piston and ring replacement may be required every 20-50 hours of hard use, depending on riding style and maintenance. Manual provides wear limits.
Gearbox Oil Spec:
SAE 80 or 90 GL-4 Hypoid Gear Oil (e.g., Kawasaki Genuine Gear Oil 10W-40 or equivalent API GL-4 rated oil).
Fork Oil Type:
Typically a suspension fluid with a viscosity of around 5W or 7.5W. Manual will specify exact type and quantity.
Coolant Spec:
50/50 mixture of distilled water and ethylene glycol-based antifreeze.
Common Wear Items:
Clutch plates, piston rings, spark plugs, chain and sprockets, wheel bearings, steering head bearings, and fork seals are common wear items requiring regular inspection and replacement.
Power Valve Maintenance:
The KIPS system requires periodic cleaning to ensure proper operation and prevent sticking, which can affect engine performance.
Carburetor Cleaning:
Carburetors can become clogged with debris or gummed up if fuel sits for extended periods, requiring regular cleaning and potentially re-jetting.
