Historical Context:
The 1991 Polaris 400 was part of Polaris's extensive snowmobile lineup, catering to a broad range of riders seeking reliable performance for recreational trail riding and moderate powder conditions.
Key Competitors:
Competed against models from Ski-Doo, Yamaha, and Arctic Cat in the mid-range performance segment.
Engine Type:
Likely a liquid-cooled, two-stroke engine, providing a good balance of power and efficiency for its class.
Suspension Type:
Typically featured a robust independent front suspension (IFS) and a rear skid frame with adjustable shocks for comfort and control.
Track System:
Standard track width and length designed for versatility on groomed trails and in mixed snow conditions.
Value Proposition:
This service manual provides essential information for maintaining, troubleshooting, and repairing the 1991 Polaris Snowmobile 400, empowering owners and technicians to keep the vehicle in optimal working condition.
Engine:
Complete engine overhaul, disassembly, assembly, inspection, tuning, and component diagnostics.
Fuel System:
Carburetor tuning, cleaning, rebuilding, fuel pump operation, fuel lines, and fuel tank maintenance.
Ignition System:
CDI unit, ignition coils, spark plugs, wiring diagrams, timing adjustments, and troubleshooting.
Cooling System:
Radiator, coolant flow, fan operation, thermostat, and coolant mixture specifications (if applicable).
Exhaust System:
Muffler, exhaust pipe maintenance, leak detection, and gasket replacement.
Drivetrain:
Clutch (primary and secondary), drive chain/belt, sprockets, gears, and track system maintenance.
Suspension System:
Front and rear suspension components, shock absorbers, springs, bushings, and alignment specifications.
Steering System:
Handlebars, steering post, tie rods, ski spindles, and steering linkage adjustments.
Braking System:
Brake caliper, rotor, master cylinder, brake fluid specifications, bleeding procedures, and adjustment.
Electrical System:
Battery, lighting, starter motor, wiring harnesses, fuses, switches, and handlebar controls.
Bodywork And Chassis:
Body panels, seat, windshield, hood removal/installation, and frame inspection.
Maintenance:
Scheduled maintenance, lubrication points, filter replacement, spark plug gap checks, and pre-ride inspections.
Troubleshooting:
Diagnostic charts, common problem identification, and step-by-step solutions for various performance issues.
Repair:
Detailed repair instructions for all major components, including engine rebuilds, transmission servicing, and suspension overhauls.
Disassembly And Assembly:
Complete step-by-step guides for dismantling and reassembling all vehicle systems and components.
Cleaning And Inspection:
Guidelines for cleaning components and thorough inspection procedures to identify wear and damage.
Level:
Comprehensive, suitable for both novice mechanics and experienced technicians.
Diagnostics:
In-depth diagnostic procedures, including electrical system testing and engine performance analysis.
Rebuilds:
Detailed instructions for complete engine and component rebuilds, including torque specifications and clearances.
Type:
Two-Stroke, Reed Valve
Displacement:
Approximately 398cc (Specific bore and stroke details would be in the manual)
Cylinder Arrangement:
Single Cylinder
Horsepower:
Estimated 50-65 HP (Varies with tuning and specific model variant)
Torque:
N/A (Specific figures typically not advertised, but performance characteristics are detailed in the manual)
Carburetor:
Single Mikuni VM carburetor (Specific model and size details available in manual)
Fuel Type:
Unleaded Gasoline (Minimum 87 Octane Recommended)
Oil Mixture:
Premix (50:1 ratio with quality 2-stroke oil recommended, specific oil type detailed in manual)
Length:
N/A (Specifics available in manual, generally around 100-110 inches)
Width:
N/A (Specifics available in manual, generally around 40-48 inches)
Dry Weight:
Estimated 450-500 lbs (Specifics available in manual)
Fuel Capacity:
Approximately 6-7 gallons (Specifics available in manual)
Length:
N/A (Typically 121 inches)
Width:
N/A (Typically 15 inches)
Lug Height:
N/A (Typically 0.75 to 1.0 inch)
General:
Snowmobiles of this era do not have standardized safety ratings like automobiles. Emphasis is on proper operation and maintenance.
Braking System:
Hydraulic disc brake system for reliable stopping power.
Throttle Control:
Thumb throttle with safety detent to prevent accidental acceleration.
Kill Switch:
Handlebar-mounted emergency kill switch (lanyard type may be optional or aftermarket).
Lighting:
Headlight and taillight for visibility.
Manual Recommendations:
The manual will include crucial safety operation guidelines, warnings, and recommended safety gear.
Oil Change:
N/A (2-stroke, requires regular premixing)
Spark Plug Check:
Every 50-100 hours of operation or as specified in manual.
Clutch Inspection:
Regular inspection of clutch sheaves, rollers, and springs for wear and damage, particularly before and after heavy use.
Drive Belt Inspection:
Check for wear, cracks, and proper tension at regular intervals, recommended annually or every 1000 miles.
Carburetor Cleaning:
Recommended annually or if performance issues arise, especially after storage.
Coolant:
Ethylene glycol based antifreeze, mixed with distilled water (50/50 ratio). Specific type and capacity detailed in manual.
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid (Check manual for exact specification and bleeding procedures).
Clutch Wear:
Common issue due to heat and friction; requires periodic inspection and adjustment/replacement of belt, rollers, and springs.
Carburetor Icing:
Can occur in very cold, humid conditions; manual provides troubleshooting steps.
Suspension Bushings:
Wear and tear on suspension bushings can lead to play and reduced handling; replacement procedures are covered.
Electrical Connections:
Corrosion or loose connections in wiring can cause intermittent electrical issues; manual details wiring diagrams and troubleshooting.
