1987 KTM 250 Repair Manual

The 1987 KTM 250 is a high-performance two-stroke motocross motorcycle featuring a 249cc liquid-cooled engine, 6-speed transmission, WP suspension components, and advanced chassis design. This comprehensive repair manual covers complete disassembly, maintenance procedures, troubleshooting, and reassembly instructions for all major systems including engine, transmission, suspension, brakes, electrical, and chassis components.

1. Technical Specifications 2. Engine Repair Procedures 3. Transmission & Clutch 4. Suspension Systems 5. Brake Systems 6. Electrical System 7. Fuel System 8. Chassis & Frame 9. Maintenance Schedule 10. Torque Specifications 11. Troubleshooting Guide

Technical Specifications

Complete technical data for the 1987 KTM 250 motocross motorcycle.

Component	Specification
Engine Type	Single cylinder, two-stroke, liquid-cooled
Displacement	249cc
Bore x Stroke	67mm x 70mm
Compression Ratio	8.5:1
Transmission	6-speed constant mesh
Carburetor	Mikuni VM36SS
Ignition	CDI electronic ignition
Front Suspension	WP USD forks, 300mm travel
Rear Suspension	WP monoshock, 320mm travel
Front Brake	Single disc, 260mm
Rear Brake	Single disc, 220mm
Dry Weight	102kg (225 lbs)

Engine Repair Procedures

Complete engine disassembly, inspection, and reassembly instructions.

Engine Removal: Disconnect all cables, hoses, and electrical connections before removing engine from frame.
Cylinder Head: Remove and inspect for warpage; check combustion chamber for carbon buildup.
Cylinder & Piston: Measure cylinder bore wear; inspect piston and rings for scoring and wear.
Crankshaft: Check runout and bearing clearance; replace if beyond service limits.
Reed Valve: Inspire reed petals for cracks or improper seating; replace if necessary.

WARNING! Always use proper engine stand and lifting equipment. Engine components are heavy and can cause serious injury if dropped.

Transmission & Clutch

Transmission disassembly, gear inspection, and clutch service procedures.

Clutch Removal: Drain oil, remove clutch cover, and disassemble clutch components.
Transmission Disassembly: Split engine cases to access transmission gears and shafts.
Gear Inspection: Check all gears for worn or damaged teeth; measure shaft diameters.
Shift Mechanism: Inspect shift forks, drum, and mechanism for wear.
Reassembly: Follow precise alignment procedures for proper gear engagement.

CAUTION! Transmission components must be properly aligned during reassembly to prevent premature failure.

Suspension Systems

Front Forks: WP USD 43mm, oil capacity 480ml per leg, spring preload adjustable.
Fork Disassembly: Remove fork caps, drain oil, disassemble damping components.
Fork Seals: Replace if leaking; use proper seal driver for installation.
Rear Shock: WP monoshock with adjustable rebound damping and spring preload.
Shock Service: Nitrogen recharge required after disassembly; professional service recommended.
Linkage Bearings: Inspect and lubricate all pivot points regularly.

Brake Systems

Front and rear disc brake service, pad replacement, and bleeding procedures.

Front Brake: Single 260mm disc with twin-piston caliper. Rear Brake: Single 220mm disc with single-piston caliper.

Brake Pad Replacement: Remove caliper, extract retaining pins, install new pads. Brake Bleeding: Use DOT 4 brake fluid, follow proper bleeding sequence to remove air. Rotor Inspection: Check for warpage and minimum thickness specifications. Master Cylinder: Rebuild kits available for worn components.

Electrical System

Complete wiring diagram, component testing, and repair procedures.

Disconnect battery before performing any electrical work.
Use multimeter to test continuity and voltage at all connections.
Inspect all wiring for chafing, corrosion, or damage.
Test stator output and CDI unit for proper ignition function.

Tip: Always use dielectric grease on electrical connections to prevent corrosion.

Fuel System

Carburetor service, jetting specifications, and fuel delivery system.

Carburetor Removal: Disconnect throttle cable and fuel line, remove mounting clamps.
Disassembly: Remove float bowl, jets, needle, and slide for cleaning.
Jetting Specifications: Main jet #420, pilot jet #45, needle clip position #3.
Float Level: Set to 21mm from carburetor body mating surface.
Air Screw: Initial setting 1.5 turns out from lightly seated position.
Fuel Filter: Replace if clogged; inspect fuel lines for cracks.
Reed Valve: Inspect for proper sealing and petal condition.

WARNING! Gasoline is highly flammable. Work in well-ventilated area away from ignition sources.

Chassis & Frame

Frame inspection, steering head bearing service, and swingarm maintenance.

Maintenance Schedule

Regular maintenance intervals and service requirements.

After Every Ride: Clean air filter, check tire pressure, inspect for loose fasteners. Every 10 Hours: Change transmission oil, check chain adjustment. Every 20 Hours: Clean carburetor, repack silencer, check spoke tension. Every 50 Hours: Rebuild suspension, replace brake fluid, inspect wheel bearings.

Torque Specifications

Critical fastener torque values for proper assembly.

Component	Torque Value
Cylinder Head Nuts	20 Nm (14.7 ft-lbs)
Spark Plug	25 Nm (18.4 ft-lbs)
Clutch Spring Bolts	8 Nm (5.9 ft-lbs)
Front Axle Nut	60 Nm (44.3 ft-lbs)
Rear Axle Nut	90 Nm (66.4 ft-lbs)
Sprocket Bolts	35 Nm (25.8 ft-lbs)
Fork Clamp Bolts	20 Nm (14.7 ft-lbs)

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
Hard starting	Fouled plug, compression loss	Replace spark plug; check compression; clean carburetor.
Poor performance	Clogged jets, air leak	Clean carburetor; check reed valve; inspect crank seals.
Transmission noise	Worn gears, low oil	Check oil level; inspect transmission gears for wear.
Oil leakage	Worn seals, loose fasteners	Replace crank seals; check case half sealing surfaces.
Electrical failure	Bad connections, failed stator	Test stator output; check all electrical connections.

Technical Support: Contact authorized KTM dealer for complex repairs and genuine parts.

Parts Availability: Many original 1987 KTM 250 parts still available through KTM Classic Parts program.