1970s–1980s Husqvarna 50 / 50 Special / 51 / 55 Chainsaw Workshop Manual (P/N 531 03 00-76)

Husqvarna Workshop Manual 531 03 00-76 covers repair of the 1970s–1980s 50, 50 Special, 51, and 55 chainsaws, with model-specific engine, fuel system, and chain drive information.

Text search, navigation, and page detail: Much of the workshop text is searchable, but some image-based passages and headings are not. Bookmarks lead only to the dealer page and manual start. Text and artwork overlap at the bottom of PDF page 38 in the carburetor section.

• Engine repair: Cylinder and piston removal, piston ring replacement, crankcase splitting, crankshaft bearing installation, and crankshaft seal replacement.

• Fuel system: Walbro WA and WT carburetor disassembly, pressure testing, reassembly, and adjustment, plus fuel tank ventilation testing and fuel filter replacement.

• Ignition and starting: Electronic ignition diagnosis, flywheel removal and timing alignment, ignition module air gap adjustment, and recoil starter repair.

• Clutch and lubrication: Centrifugal clutch inspection and reassembly, rim and spur sprocket checks, and automatic oil pump disassembly and assembly.

• Safety equipment: Inertia and manual chain brake function checks, brake band replacement, throttle trigger lockout repair, chain catcher inspection, and anti-vibration element replacement.

• Diagnostic references: Troubleshooting charts, crankcase/cylinder leakage test data, carburetor cross-section schematics, exploded assembly drawings, and component-specific service specifications.

This manual is suited to mechanics familiar with two-stroke engine repair and equipped for pressure testing and crankshaft service.

Walbro Carburetors and Fuel System Diagnosis

The 50 and 50 Special use the Walbro WA82; the 51 and 55 use the WT170. The fuel chapter distinguishes their fuel circuit plate and Welch plug arrangements, fuel inlet lever settings, and the choke-operated fast idle system on the 51 and 55.

Carburetor overhaul: Carburetor Operation cutaways show the metering, mixing, and pumping sections. Exploded views show diaphragm and gasket arrangements, while pressure-test setup views support leakage checks. The overhaul cautions explain how damage to internal fuel passages and seats can require replacement of the carburetor.

Intake manifold service covers the fuel pump pulse passage, its seal, and the rubber intake tube. Throttle and choke linkage installation sits alongside basic and final carburetor adjustment, with pressure gauge P/N 5025038-01 and tachometer P/N 5027114-01 identified for the relevant tests.

Fault isolation: The two-page Trouble-shooting Chart links starting, idle, acceleration, deceleration, and high-speed complaints to possible fuel, air, metering, and circuit plate faults. This helps narrow a running problem before selecting components for inspection.

Flywheel Variants and Ignition Testing

The Model 50 serial break at 9250857 identifies the cast-in flywheel key and changes in service-tool application. Removable-key and dual-keyway flywheels are also described, with the timing alignment needed for the latter.

Ignition diagnosis covers the stop switch, short-circuit wire, high-tension lead, and ignition module. Starter service includes the rope, rewind spring cassette, and flywheel starter pawls and springs.

Cylinder, Crankcase, and Crankshaft Repair

The Cylinder & Piston fault/remedy table addresses seizure marks, cylinder coating damage, and stuck piston rings. Bearing service covers removal from the crankcase halves and installation using heated bearing seats.

The crankshaft inspection section distinguishes axial connecting-rod movement from radial play. A defective crankshaft requires replacement as an assembly. Crankcase separation uses removal tool P/N 5025161-01; seal installation is illustrated with tool P/N 5025079-01.

Chain Brake, Clutch, and Oil Pump Service

Clutch shoe and brake band wear limits accompany the inspection procedures. Flywheel, clutch, and crankcase torque specifications appear with their assembly instructions.

Oil pump coverage extends to the drive gear, pump piston and cylinder, pickup filter, and oil tank vent. The exhaust section explains how a restricted spark arrester screen can cause overheating and piston or cylinder damage.

Keep in mind that this is an informational overview. Use the complete manual for service procedures, particularly work on the tensioned chain brake and rewind springs.

Printable Workshop PDF and Included Dealer Page

The download is a single printable, English-language 59-page PDF: 58 manual pages, including the cover, introduction, and 56 numbered pages, plus one banner page. The dealer page is already included in the total.