Historical Context:
Husqvarna motorcycles, particularly in the late 1970s, were renowned for their off-road prowess, especially in motocross and enduro disciplines. The 390 CR was a significant model in their competitive lineup.
Competitors:
Competed against other European and Japanese manufacturers in the motocross segment, such as KTM, Maico, Suzuki, Yamaha, and Honda.
Performance Orientation:
Designed for competitive motocross, emphasizing power, suspension travel, and durability for demanding off-road conditions.
Diagnostic Aid:
Crucial for diagnosing wear and identifying correct replacement parts for maintenance and repair, preventing misidentification and incorrect purchases.
Restoration Resource:
Essential for owners undertaking restoration projects, ensuring the use of period-correct and original specification parts.
Preventative Maintenance:
Helps owners identify parts that are commonly replaced during routine maintenance or after significant wear.
Engine Components:
Piston, rings, cylinder, cylinder head, crankshaft, connecting rods, bearings, valves, camshaft, timing gears/chain, oil pump, oil seals, gaskets.
Transmission Components:
Gear sets, input/output shafts, clutch components, shift forks, synchronizers (if applicable), bearings, seals, gaskets.
Frame And Chassis:
Frame sections, subframes, swingarm, linkages, fasteners.
Suspension Components:
Front forks (internal components, seals, springs), rear shock absorbers, linkages, bushings.
Braking System Components:
Brake levers, master cylinders, brake lines, calipers, brake pads, brake discs/drums, actuating rods, seals, gaskets.
Electrical Components:
Ignition coil, stator, rotor, wiring harness, switches, lights (headlight, taillight, brake light), battery terminals/cables.
Fuel And Carburetion:
Carburetor (internal components, jets, floats, gaskets), fuel tank, fuel lines, fuel filter, petcock.
Exhaust System Components:
Exhaust pipe, muffler, clamps, gaskets.
Controls And Levers:
Handlebars, grips, throttle assembly, clutch lever, brake lever, cables, linkages.
Body Panels And Fittings:
Fenders, side panels, fuel tank shrouds, seat, number plates, fasteners, grommets.
Parts Identification:
Detailed diagrams with exploded views and part numbers for all components.
Cross Referencing:
Ability to cross-reference part numbers for potential interchangeability (though primarily focused on OEM).
Assembly Guidance:
Visual guidance on how parts fit together.
Troubleshooting Support:
Indirectly supports troubleshooting by identifying correct replacement parts.
Depth:
Comprehensive for parts sourcing and identification. Focuses on visual representation and part numbers rather than repair procedures.
Engine Type:
2-stroke, Single-cylinder
Displacement:
Approximately 363 cc (22.1 cubic inches). Exact displacement for '390' models could vary slightly by year or sub-model.
Bore X Stroke:
Not specified, but typical for this era might be around 76mm x 80mm.
Cooling System:
Air-cooled
Horsepower:
Estimated 35-45 hp (power output varied significantly by tuning and specific model year).
Torque:
Not specified, but emphasized low-to-mid-range grunt for off-road use.
Carburetor:
Single Mikuni VM series (e.g., VM34 or VM36) or Bing carburetor.
Fuel Type:
Unleaded gasoline with 2-stroke oil mixture (pre-mix).
Ignition Type:
Magneto ignition, potentially CDI (Capacitive Discharge Ignition) for later models.
Piston Ring Replacement:
Recommended every 30-50 hours of competition use, or based on compression loss.
Top End Rebuild:
Recommended every 60-100 hours of competition use, or as needed based on performance.
Spark Plug Replacement:
Frequent replacement (every 10-20 hours) is common for 2-stroke motocross bikes, depending on plug type and heat range.
Chain And Sprockets:
Regular cleaning, lubrication, and adjustment; replacement based on wear indicators (stretch, hooked teeth).
Air Filter Cleaning:
After every ride in dusty conditions.
2-Stroke Oil:
High-quality 2-stroke racing oil (e.g., Motul, Castrol) mixed at a ratio specified by the manual or manufacturer, typically 20:1 or 25:1.
Transmission Oil:
Gear oil, typically SAE 80W or 10W-30 for the gearbox. Specific viscosity would be in the manual.
Carburetion Tuning:
Sensitivity to jetting changes based on altitude, temperature, and humidity; can be finicky to get right.
Clutch Wear:
Clutch plates and springs can wear out due to hard use.
Suspension Seals:
Fork seals and rear shock seals are prone to leaks with heavy use.
Ignition Reliability:
Older magneto and CDI systems can be prone to failure or require specialized testing equipment.
Brand Origin:
Husqvarna is a Swedish brand with a long history dating back to the 17th century, famously involved in firearms and later, motorcycles, particularly in off-road disciplines.
Cr Series Development:
The CR (Competition / Motocross) series was central to Husqvarna's identity, evolving from early Swedish scramblers to highly competitive motocross machines that dominated early international events.
Production Period:
The 390 CR was a key model in Husqvarna's late 1970s motocross range, contributing to their reputation before the significant influx of Japanese manufacturers changed the landscape.
Historical Racing Success:
Husqvarna motorcycles, including models like the 390 CR, achieved significant success in motocross and enduro racing throughout the 1970s, earning numerous championships and accolades.
Owner Satisfaction:
Highly regarded by enthusiasts for their raw performance and handling, but maintenance intensity and parts availability are factors.
Historical Certifications:
N/A for this type of off-road vehicle from this era.
