Honda CB125/CB160 Shop Manual, 1972 (P/N 622161)

This factory shop manual covers the Honda CB125 and CB160 parallel twins. The manual (P/N 622161) carries a 1972 copyright and was issued by the Service Department of Honda Motor Co., Ltd.’s Foreign Sales Division.

PDF Navigation and Diagram Detail

Text search and diagram labels: The PDF lacks text search and embedded bookmarks. Zoom in to read small terminal numbers and wire-color labels in the electrical drawings.

The ZIP contains one printable English-language PDF with 139 pages. That total includes the original cover, the preface and contents pages, three blank pages, four pages of maintenance specifications, and a wide foldout page.

Engine, Chassis, and Electrical Service

These selected workshop topics show the range of repairs and checks covered. The manual also includes headlight beam checks and speedometer inspection.

• Engine overhaul: Engine removal and installation, cylinder head and camshaft service, valve-seat work, crankcase separation, and crankshaft, connecting rod, and piston inspection.
• Clutch and gearbox: Wet multiplate clutch disassembly, transmission gear and shift-fork inspection, and kick-starter service.
• Carburetors and lubrication: Dual-carburetor cleaning, adjustment, and synchronization, plus service of the oil pump, filters, and separator.
• Chassis and brakes: Front fork, steering stem and handlebar lock, swingarm and rear shocks, wheel bearings, and front and rear drum brakes.
• Electrical diagnosis: Ignition and charging checks, starter motor and solenoid service, and wiring diagrams for individual circuits.
• Maintenance references: Periodic inspection schedules, chassis fastener torques, model-specific service limits, and illustrated special tools.

Honda’s preface identifies mechanics and sales staff as readers who need to understand how the assemblies are serviced.

Engine Assembly and Wear Checks

The assembly illustrations show cam-chain timing and the cylinder-head tightening sequence. The crankshaft section covers bearing and oil-passage alignment, and the crankcase procedures address gasket and O-ring inspection. Honda warns that reversing a marked piston can bring its crown into contact with the valves.

The wide engine exploded view shows how the clutch, gear shafts, and crankcase assemblies fit together. The special-tool plate identifies the drive-sprocket holder, valve lifter, rotor and bearing pullers, piston ring tool and slider, steering-stem socket, and fixtures for the fork and rear shocks.

Fuel Delivery and Oil Circulation

The carburetor chapter separates pilot, midrange, and main-circuit adjustments. It explains jet and needle selection, float-height inspection, idle setting, and how to compare left and right throttle openings through full travel. The separate model columns let you check the correct carburetor settings when tracing uneven running after fuel-system work.

The lubrication diagram traces oil flow through the plunger pump, wire-mesh screen, centrifugal filter, and internal passages. The troubleshooting notes identify pump wear, blocked passages, and other causes of poor circulation.

Frame, Wheels, and Brake Adjustment

The chassis chapters cover the fuel tank and petcock, frame and steering damper, seat and air cleaners, center stand, and exhaust. Wheel service includes checking rims, spokes, axles, brake shoes and cams, fitting tires and tubes, and aligning the speedometer drive.

The maintenance chapter covers wheel alignment, drive-chain tension, and front and rear brake adjustment. Its inspection schedule distinguishes owner checks from dealer service. Secure the motorcycle for wheel and brake work, keep ignition sources away during fuel work, and isolate electrical power where the procedure calls for it.

Ignition, Charging, and Starting

Honda explains how the battery ignition fires both plugs on the 360-degree twin. The chapter covers breaker points, condenser testing, centrifugal advance, and spark-plug diagnosis. It also includes an ignition-coil spark-performance graph, an AC-generator charging curve, and silicon rectifier terminal checks.

The starter section covers the planetary reduction gears and the roller clutch behind the generator rotor. It describes the emergency kick-start circuit and warns that incorrect rectifier wiring or running the generator with the battery disconnected can damage the silicon rectifier. Other electrical references cover the horn, neutral indicator, combination switch, and harness wire identification.

Compression, Tappet, and Float-Height Examples

For both models, Honda gives a warm compression range of 128–149 psi with the throttle and choke fully open. The intake and exhaust tappet clearance is 0.03–0.05 mm on a cold engine at top dead center on the compression stroke.

The maintenance table lists a carburetor float height of 26 mm for the CB125 and 19.5 mm for the CB160.