1940–1947 Harley-Davidson Big Twin O.H.V. & Side Valve Service Manual (P/N 12022-44D)

This Harley-Davidson service manual covers 1940–1947 O.H.V. and Side Valve Big Twins, including E, EL, F, FL, U, UL, UH, and ULH configurations. Coverage extends from initial servicing and scheduled maintenance to engine, transmission, electrical, and chassis repair.

• Engine overhaul: In-frame top-end work, engine removal, crankcase disassembly, cylinder and valve service, piston fitting, and bottom-end bearing inspection.

• Lubrication: O.H.V. gear-type and Side Valve vane-type feed pumps, scavenger pumps, crankcase breather timing, and drive-chain oiling.

• Electrical diagnosis: Generator field-coil and armature tests, cut-out relay and regulator checks, ignition circuit breaker service, and equipment-specific wiring diagrams.

• Carburetor service: Mixture adjustment, float-valve inspection, passage cleaning, throttle-disc identification, and sectional views of the fuel and idle circuits.

• Transmission and clutch: Internal inspection, reassembly, shifter mechanism checks, and separate service instructions for the earlier and later clutch assemblies.

• Brakes and chassis: Brake relining, wheel-hub service, wheel spoking and truing, fork removal, steering damper assembly, saddle spring post service, and sidecar attachment.

This manual suits mechanics familiar with vintage Big Twin assemblies and equipped for precision fitting; its overhaul procedures call for micrometers, reamers, pullers, and a flywheel truing fixture.

Engine Fitting and Oil Circulation

The engine chapters distinguish top overhaul with the engine base in the frame from complete removal and lower-end work. Detailed procedures cover cylinder reboring and honing, valve-seat grinding and testing, and piston-pin and ring fitting. Piston fitting data is qualified for genuine Harley-Davidson taper-cam-ground pistons.

Bottom-end coverage reaches line reaming cam gear shaft bushings, sizing connecting-rod lower races, and truing flywheels with fixture 11962-X. Replacement of connecting-rod lower races is referred to the factory; the workshop procedures explain lapping and refitting serviceable races.

The Trouble Chart groups symptoms such as hard starting, overheating, excessive oil use, and transmission engagement faults. The Lubrication Chart and oil-pump schematics distinguish feed, bypass, and return paths, helping trace circulation problems on the two engine designs.

Oil-pump service notes warn that incorrect gasket thickness or misplaced oil holes can interrupt lubrication and damage the engine. The O.H.V. section also links leaking push-rod cover cork seals to impaired oil return, flooded valve spring covers, external leaks, and fouled plugs.

Working on vintage V-twins requires strict adherence to factory tolerances and proper tooling to prevent critical engine damage or personal injury.

Generator Tests and Wiring Variants

Charging-system coverage distinguishes standard 32E and radio 32E2/32E2R generators, with separate checks for three-brush and two-brush arrangements. Field-coil tests and growler tests for grounded, shorted, or open armatures help isolate charging faults before parts are replaced.

Wiring diagrams separate systems with and without a current-and-voltage regulator. The 1947 diagrams cover standard lighting, accessory lamps, and police/radio equipment; separate sidecar diagrams distinguish early and later arrangements. Ignition coverage includes circuit breaker overhaul and timing by flywheel mark or piston position.

Carburetor and Transmission Service

Carburetor coverage identifies O.H.V. M-25, M-35, and M-75 units and Side Valve M-51 and M-51L units. The sectional views explain idle passages and float operation, while the service text addresses deposits, bowl leakage, and throttle-disc matching.

Throttle-shaft bushing replacement is illustrated; its complete instructions accompany tool set 12012-44D. Transmission main-drive-gear oil-seal replacement and shifter-fork gauge checks likewise refer to instructions supplied with tools 12734-42 and 12074-39, respectively.

Gearbox assembly drawings distinguish the main-drive-gear, mainshaft/countershaft, and shifter-fork groups. Clutch exploded views support disc and spring identification, and the fitting summaries give bearing clearances, endplay, and engagement checks.

Forks, Wheel Hubs, and Sidecars

Chassis procedures cover hub bearing fitting, brake shoe relining, spring-fork removal and installation, and rough checks of fork, frame, and handlebar alignment. Major fork straightening is referred to a properly equipped shop.

Saddle spring post combinations, Ride Control assembly, and sidecar mounting and brake adjustment are also covered. The Monroe hydraulic shock absorber has an assembly illustration and parts list; its servicing is referred to separate bulletin 258.

Selected Cold Tappet and Ignition Clearances

For the Side Valve engine, the cold tappet-clearance section specifies .004–.005 in. for intake valves and .007–.008 in. for exhaust valves. O.H.V. tappets have a separate adjustment method based on free push-rod rotation.

Ignition service data specifies a .022-inch circuit breaker point gap with the rubbing block at the highest point of the cam. These settings accompany the manual’s component-specific inspection and adjustment procedures.

PDF Reading and Diagram Detail

Search, navigation, and wiring labels: PDF text search and embedded bookmarks are not available. Small wire-color labels and component numbers in the wiring diagrams are best read with zoom.

Supplied as one printable 165-page PDF in English. The total includes the title/sectional-index page, foreword, and two full Memoranda pages, with a detailed index at the end.