Honda CB350F / CB400F Four 1975–78 Shop Manual (P/N 623231)

Honda’s Shop Manual (P/N 623231) uses the 1972 CB350F Four as its base model and includes the CB400F supplement for changes to the engine, chassis, and electrical system. The CB400F supplement provides gearbox service data and shift-pedal linkage adjustment. The internal transmission teardown and exploded view cover the CB350F assembly.

PDF Files and Wiring Diagram Readability

Text search and diagram detail: The PDFs have no text search or embedded bookmarks. The printed contents page lists chapters for both models. Small wire-color codes in the CB350F wiring diagram are easier to read after zooming in. Some codes in the denser areas of the CB400F diagram remain faint even when enlarged.

The ZIP contains 113 pages across 10 printable PDFs. Files 01–08 contain the original cover and the 86-page CB350F base section. Files 09–10 contain the 26-page CB400F supplement.

Engine, Chassis, and Electrical Service

These are selected topics from the manual. The supplement also includes CB400F side-stand return checks and fuel-filter service.

• Engine and valve train: Step-by-step engine removal, cylinder-head and piston disassembly, valve timing, and cam-chain tensioner service. An on-bike service chart shows which jobs can be done with the engine in the frame.
• Clutch and primary drive: Wet multi-plate clutch inspection, primary drive chain and shaft disassembly, starter-clutch checks, and gearshift mechanism service.
• Carburetor adjustment: Vacuum-gauge synchronization, fast-idle and overtravel-stop adjustment, and throttle-cable setup.
• Brake repair: Front master cylinder and caliper service, pad inspection, caliper adjustment, hydraulic bleeding, and rear drum brake inspection.
• Wheels and suspension: Wheel-bearing service, wheel balancing, steering stem adjustment, front fork seal replacement, and swingarm bushing checks.
• Electrical diagnosis: Charging tests, ignition timing, starter checks, switch continuity tests, and separate wiring diagrams for the CB350F and CB400F.

Honda wrote this shop manual for mechanics servicing the CB350F and CB400F.

Engine Teardown, Bearings, and Lubrication

Cylinder-head inspection covers valve-seat contact, valve-guide replacement, and camshaft bearing checks. For much of the engine and frame reassembly, Honda pairs the reverse of the teardown sequence with component-specific reassembly notes. The CB400F supplement adds piston ring assembly and clutch disassembly details.

Crankshaft and connecting rods: Plastigage checks help determine whether bearing clearances are within limits. The bearing selection tables match journal measurements and rod codes to bearing grades, and a separate chart groups replacement connecting rods by weight.

The Lubricating Oil Circuits diagram traces pressure and splash lubrication through the engine and transmission. The surrounding section covers the double trochoid oil pump, relief-valve inspection, and two-stage filtration.

Carburetors, Brakes, and Suspension

Carburetor teardown covers throttle valves and jet needles, float-valve service, jet inspection, and fuel-level adjustment. The CB400F supplement includes its own carburetor setting table and covers breather-element cleaning and drain-tube service for the Blow-by Gas Circulator.

The frame section includes fuel-cock disassembly and muffler removal. The supplement details the revised front fork internals and rear shock absorber assembly. The front brake chapter identifies the master cylinder’s primary cup as vulnerable to damage during installation.

Charging, Ignition, and Starting Systems

The CB350F section covers field- and stator-coil checks for the three-phase AC generator, silicon rectifier testing, and contact adjustment for the Tirrill-type voltage regulator. Mechanics can use the Charging Test Circuit and output table together to decide whether a charging fault calls for generator or regulator checks.

Ignition coil and spark advancer tests, starter motor brush and armature inspection, and main switch continuity checks help narrow down electrical faults. The CB400F supplement shows the charging circuit with a contactless regulator and the starting circuit with a clutch switch. Its diode test notes warn that a high-voltage insulation tester can damage the starter-circuit silicon diode. The CB400F Routing drawings show cable, hose, and harness placement.

Maintenance Schedules, Troubleshooting, and Tools

Both models have maintenance schedules and tables for tightening torques, assembly standards, wear limits, fluid capacities, and electrical test values. The CB350F troubleshooting charts link hard shifting, clutch slip, wheel wobble, and charging faults to probable causes. The CB400F tool list identifies the clutch locknut wrench 07916-6390000 and the optional carburetor synchronization wrench set 07908-3230200.

For brake work or repairs involving loaded suspension springs, use the applicable service data and work within your technical training or under qualified supervision.

Sample Carburetor and Fork Specifications

For a warmed-up CB350F, the carburetor synchronization check calls for matching vacuum readings across all carburetors within a specified range of 16–24 cmHg.

The CB400F supplement specifies 145–150 cc of ATF per fork leg after draining and 160–165 cc per leg after disassembly, when the fork is dry.