Chainsaw STIHL 051, 076 Service Manual (P/N 0455 111 0123)

This 256-page PDF is a mixed OEM manual set, not a single 256-page 051/076 repair manual. Its core document is the English STIHL Service Manual, Form No. 0455 111 0123: 76 PDF pages, including 72 numbered service pages, for the 050 AV, 051 AV, 051 AV electronic, 075 AV electronic, and 076 AV electronic. It was written for STIHL servicing dealers and staff, so it is suited to experienced two-stroke technicians with access to the listed pullers, gauges, testers, and assembly fixtures.

• Document breakdown: 76-page service manual; 32-page 048 (1117) spare-parts list; 34-page 050/051 (1111) parts list included twice, accounting for 68 pages; 38-page 056 (1115) list; and 42-page 064 (1122) list. The illustrated parts books are July 2004 editions.
• Powerhead repair: Covers cylinder and piston removal, piston fitting, crankcase separation, crankshaft and bearing installation, oil-seal replacement, and crankcase pressure and vacuum testing.
• Drive, brake, and starter work: Details the centrifugal clutch, Quickstop isolating clutch, chain brake, friction-shoe rewind starter, AV handle system, and throttle mechanism, with disassembly, repair, and inspection procedures.
• Ignition diagnosis: Separates breaker-controlled magneto service from Bosch transistor-controlled breakerless ignition, including component tests, static timing work, stroboscopic checks, and magneto edge-gap adjustment.
• Fuel and lubrication systems: Explains the pulse-operated diaphragm carburetor and integral fuel pump, then covers carburetor leakage testing and repair, automatic and manual chain-oil pumps, tank vents, pickup systems, and oil-delivery adjustment.
• Troubleshooting and illustrations: Seven fault-isolation charts cover the clutch/chain brake, engine, both ignition types, rewind starter, chain lubrication, and carburetor. Diagrams include the breaker ignition circuit, transistorized ignition schematic, rewind-starter friction-shoe layout, carburetor operating views, oil-pump component view, and chain-brake assembly.

Model and Build Differences

The service coverage applies to the 050, 051, and 075 through machine No. 5,277,720 and to later machines unless STIHL issued updated repair procedures. STIHL states that the newer 076 and the 075 are identical except for the rewind starter and ignition system; those engineering changes are assigned to Technical Information Bulletin 27.80, which is referenced but not reproduced in this PDF.

For the 051, the manual identifies the move from breaker-controlled ignition to the breakerless system at machine No. 3,001,400, with a separate earlier timing and magneto edge-gap specification through machine No. 2,981,245. It also distinguishes the 89 cc 051 with a 52 mm bore from the 111 cc 075/076 with a 58 mm bore, and explains the earlier 051 crankshaft bearing arrangement versus later shared 051/075 crankcases.

Factory Repair Data and Tooling

This is full internal-engine material rather than a tune-up booklet. The powerhead section reaches crankcase splitting, bearing and seal work, complete crankshaft installation, and leak diagnosis. Model-specific torque tables, wear limits, clearances, ignition test values, carburetor settings, and chain-oil delivery specifications support final assembly and adjustment.

The procedures call out tools by number, including assembly stand 5910 850 3100, carburetor/crankcase tester 1106 850 2900, vacuum pump 0000 850 3500, flywheel puller 1110 890 4500, and chain-brake spring assembly tool 1117 890 0900. The complete Special Tool Manual is a separate publication; the English edition is identified as No. 0455 901 0123 and is not included here.

Illustrated Parts Coverage and Repair Cautions

Across the four unique spare-parts catalogs are 54 distinct exploded assembly plates. Coverage includes the 048 inertia chain brake, the 050/051 HS-60D and WS-11 carburetors and friction-shoe starter, the 056 HS-118B and WJ-4B carburetors, and the 064 WJ-65 carburetor and heated-handle system. The 050/051 catalog is duplicated exactly. No dedicated 075/076 illustrated parts list is included.

The engine chapter warns that the piston must face the exhaust port correctly and that cylinder misalignment can break the piston rings. During oil-pump repair, the specified assembly sleeve protects the integral rubber sealing ring from the crankshaft edge. Repairs also involve preloaded brake and rewind springs, high ignition voltage, and rotating cutting components; follow the factory safety instructions and verify every torque, clearance, and test value in the manual before hands-on work.