Motorcycle Segment:
Cruiser / Custom Motorcycle
Key Competitors Era:
Other Harley-Davidson models (e.g., FXE, FLH), Indian Chief, custom choppers, other American V-twin motorcycles.
Vehicle Identity:
The FXS Low Rider is a iconic American cruiser known for its distinctive styling, the potent Shovelhead engine, and its custom riding position. It represents a significant era in Harley-Davidson's development, blending performance with a rebellious image.
Engine Systems:
Engine assembly, disassembly, inspection, tuning, carburetor systems (e.g., Keihin, S&S), ignition systems (points and electronic), lubrication, cooling (air-cooled), exhaust systems.
Transmission Systems:
Gearbox assembly, disassembly, inspection, clutch operation, shift linkage, primary drive, secondary drive (chain).
Chassis Systems:
Frame, front fork (Garb, Shovelhead types), rear suspension (shock absorbers, swingarm), wheels, tires, bearings, steering.
Braking Systems:
Front and rear brake caliper service, master cylinder, brake lines, brake fluid specifications, rotor inspection.
Electrical Systems:
Wiring diagrams, lighting circuits, starter system, charging system (alternator, regulator), battery, ignition switch, horn, instrumentation.
Fuel System:
Fuel tank maintenance, fuel lines, fuel petcock, carburetor tuning and rebuilding.
Bodywork And Trim:
Fenders, fuel tank, seat, handlebars, foot controls, exhaust pipes, brackets, mounting hardware.
Maintenance Procedures:
Regular service checks, oil changes, filter replacements, chain adjustment, spark plug replacement, battery maintenance, brake system bleeding.
Troubleshooting Guides:
Diagnosis of common engine, electrical, and mechanical problems with step-by-step solutions.
Repair Procedures:
Detailed instructions for component removal, disassembly, cleaning, inspection, repair, and reassembly for all major systems.
Diagnostic Procedures:
Methods for checking ignition timing, compression testing, electrical circuit testing, and carburetor adjustments.
Depth Of Information:
Comprehensive, covering everything from basic maintenance to complete engine and transmission overhauls, including detailed torque specifications and clearances.
Engine Type:
Air-cooled, four-stroke, 45-degree V-twin OHV (Shovelhead)
Displacement:
80 cubic inches (1340 cc)
Bore X Stroke:
3.4375 in x 4.25 in (87.3 mm x 108.0 mm)
Compression Ratio:
Approximately 7.2:1 to 8.5:1 (depending on specific engine build and tuning)
Horsepower Est:
Approximately 65-70 HP (at the crankshaft, estimates vary)
Torque Est:
Approximately 80-85 ft-lbs (at the crankshaft, estimates vary)
Carburetor Type:
Typically Keihin butterfly or S&S Super E/G (often an aftermarket upgrade)
Fuel Type:
Unleaded gasoline, minimum 87 octane (RON+MON)/2
Ignition Type:
Contact Breaker Points or Early Electronic Ignition (e.g., Dynatech, Morris Magneto)
Transmission Type:
4-speed constant mesh, foot shift, hand clutch
Optional Transmission:
N/A for factory models of this year, but aftermarket 5-speed conversions were common.
Primary Drive:
Duplex chain drive, wet clutch
Secondary Drive:
O-ring sealed drive chain
Safety Standards Era:
Motorcycle safety standards of the early 1980s; no formal crash ratings like modern cars.
Braking System Type:
Hydraulic disc brakes, front and rear.
Lighting:
Headlight, tail light, brake light, turn signals.
Frame Construction:
Heavy-duty steel frame designed for stability and load-carrying.
Suspension:
Telescopic front forks, dual rear shock absorbers providing rider comfort and control.
Oil Change Interval:
Typically every 2,000-3,000 miles or 6 months, depending on riding conditions. Check manual for exact recommendation.
Primary Chain Case Oil Change:
Every 5,000-10,000 miles. Check manual for exact recommendation.
Spark Plug Replacement:
Typically every 5,000-10,000 miles. Check manual for exact recommendation.
Engine Oil:
Viscosity: 20W-50 (preferred for Shovelhead engines). Capacity: Approx. 3 quarts (2.8 liters) with filter. API Service Classification: SG or higher.
Primary Chain Case Oil:
Harley-Davidson Primary Chain Lubricant, or equivalent 75W-90 GL-5 gear oil. Capacity: Approx. 24 oz (710 ml).
Transmission Oil:
Harley-Davidson Transmission Lubricant, or equivalent 75W-90 GL-5 gear oil. Capacity: Approx. 1 quart (0.95 liters).
Brake Fluid:
DOT 4 or DOT 5 Silicone fluid (verify specific requirements for 1981 models, DOT 5 was becoming prevalent). Check master cylinder cap.
Shovelead Engine Common Issues:
Oil leaks (especially at cylinder base and rocker boxes), oil burning, valve guide wear, carburetor tuning challenges, weak charging systems (especially with early regulators), primary chain adjustement requirements.
Transmission Common Issues:
Clutch drag, false neutrals, worn shifter pawl and bushings.
Electrical System Common Issues:
Corroded wiring connectors, regulator/rectifier failure, headlight bulb burnout.
Brand Origin:
Founded in Milwaukee, Wisconsin, Harley-Davidson is America's oldest motorcycle manufacturer, with a legacy of building powerful, distinctive motorcycles.
Fxs Lineage:
The FXS Low Rider was introduced in 1977 as a more stylish and custom-oriented alternative to the FLH Electra Glide. It featured a longer wheelbase and unique styling cues that defined its custom look.
Shovelhead Era Production:
The Shovelhead engine was produced from 1966 to 1984, with significant updates and variations throughout its lifespan. The 1981 model represents a later iteration of this iconic engine.
