1958–1959 Harley-Davidson Duo-Glide FL / FLH 74 OHV Repair Manual (P/N 99482-59)

• Official Harley-Davidson factory service manual, Part No. 99482-59, in a 140-page PDF; direct coverage is the 1959 Duo-Glide 74 OHV, with 1958 applicability except for minor differences.
• Distinguishes FL and FLH specifications, four-speed and optional three-speed/reverse transmissions, solo and sidecar gearing, and non-adjustable versus two-position adjustable Duo-Glide fork configurations.
• Covers wheel-hub repair, wheel spoking and truing, frame alignment checks, fork disassembly and rebushing, rear suspension work, and mechanical front plus hydraulic rear/sidecar brake service and bleeding.
• Details 74 OHV top-end and lower-end repair, including valve-guide and seat work, cylinder refinishing, piston and ring fitting, connecting-rod alignment, oil-pump and hydraulic-tappet service, gear timing, crankcase overhaul, bearing fitting, and flywheel truing.
• Documents foot- and hand-clutch adjustment, clutch and starter teardown, main-drive-gear seal replacement, shifter timing and fork gauging, four-speed gearbox overhaul, and the component changes used in the three-speed/reverse unit.
• Provides a 110-item diagnostic checklist, standard and radio-special wiring information, Model 58 and 58R generator tests, and named references such as the Engine Cutaway, Adjustable Fork - Exploded View, Oil Feed Pressure System, Oil Scavenger System, Wiring Diagram, and Ignition Timing - Schematic.

1958-1959 Duo-Glide Coverage

The cover identifies this as the 1959 Duo-Glide 74 OHV manual and states that, except for minor differences, the repair information also applies to the 1958 Duo-Glide 74 OHV. It can assist with earlier 61 and 74 OHV machines, but the factory directs readers to the model-specific parts catalog when applying the procedures to pre-1959 motorcycles. The specification tables identify FL and FLH engines and separate solo from sidecar sprocket, ratio, and tire data.

Harley-Davidson presents the routine maintenance material for the general reader while addressing its factory-approved major repair methods to professional mechanics. The overhaul sections are best suited to technicians and experienced restorers equipped for precision measurement, pressing, reaming, bearing fitting, and flywheel alignment. Shared pages identify limited Servi-Car, Sportster, 165, and Hummer applications where components overlap; this is not a full service manual for those models.

Chassis and 74 OHV Engine Repair

Chassis coverage runs from wheel removal through hub bearing and shim service, spoke installation, rim centering, and truing. The fork section separates the solo-only non-adjustable assembly from the adjustable fork used for solo or sidecar operation. It covers oil service, damper diagnosis, slider and tube disassembly, bushing replacement and reaming, fork-tube and bracket alignment, rear shock spring settings, shock disassembly, and rear-fork bearing service. Brake repair includes the front drum, hydraulic rear and sidecar wheel brakes, master-cylinder repair, system bleeding, and pedal adjustment.

The engine chapters explain pressure-feed and return/scavenger oil flow before moving into engine-in-frame top-end work and complete removal for lower-end overhaul. Procedures cover cylinder-head teardown, valve guides and seats, rocker arms, tappet adjustment, cylinder measurement and refinishing, piston-ring fitting, rod-bushing replacement, oil-pump repair, hydraulic-unit testing, timing-gear installation, connecting-rod race lapping, crankshaft bearing selection, and flywheel truing. The cylinder-head material also distinguishes FL and FLH valve-spring, valve-key, and stem-pad arrangements. Carburetor adjustment and overhaul, float and needle inspection, air-cleaner service, fuel-strainer care, and fuel-tank fitting alignment round out the fuel-system material.

Gearbox and 6-Volt Electrical Repair

Transmission material covers both foot- and hand-shift controls and both clutch-control arrangements. The optional three-speed/reverse transmission is limited to hand-shift motorcycles and cannot be assembled in a four-speed case, an important parts-selection boundary. Electrical coverage includes the keyed wiring diagram, Model 58 and fan-cooled Model 58R generators, output and field-coil tests, growler tests for the armature, commutator repair, generator polarization, two-unit and three-unit regulator diagnosis, breaker-point service, ignition timing by marks and test lamp, lamps, battery, horn, and speedometer-drive service.

Factory reference data include dimensional and capacity tables, component clearances, wear limits, spring-test loads, bearing fits, shaft and gear end play, lubrication data, sprocket and transmission ratios, tire data, charging-system test values, regulator settings, and a bulb chart. Named tools include the Valve Spring Compressor P/N 96600-36, Valve Guide Reamer P/N 94830-47, Flywheel Truing Device P/N 96650-30, Pinion Gear Puller and Installer P/N 96830-51, and Fork Shifter Gauge P/N 96384-39.

The manual warns that factory-matched wheel-hub bearings and shims must remain with their original hub; mixing them can create an incorrect fit, while excess grease can contaminate the brakes. It also identifies the vented shifter-cover screw that must return to its designated hole or gearbox pressure can force oil into the clutch. Support the motorcycle securely before wheel, fork, engine, or transmission work, and follow proper precautions around fuel, compressed springs, hydraulic brakes, batteries, and electrical testing.