1979–1983 Honda CB900C / CB900F Service Manual (P/N 07Z20-MR70100)

This 367-page PDF combines Honda factory service-publication material for the CB900C and CB900F with the included 1981 CB900F addendum. The Honda material covers the air-cooled DOHC inline-four, carburetion, lubrication, engine removal and internal inspection, clutch and starter clutch, gearshift linkage, the CB900C dual-range subtransmission and shaft final drive, chassis service, hydraulic brakes, and the charging, ignition, starting, and switch circuits. The front contents sheet is dated March 1982; the base pages retain 1980 issue dates, while the CB900F addendum is dated July 1981 and includes later revised sheets.

Model Identification & Configuration Differences

Model identification is specific enough to check the motorcycle before ordering parts or choosing a repair procedure. The CB900C base pages identify machines beginning with frame No. SC04-2000046 and SC04-2001669 for Canada. The included ’81 CB900F addendum begins with frame No. SC01-0000021.

That distinction is mechanically important. CB900C specifications list a 901 cc engine with 9.2:1 compression, a five-speed transmission, Honda’s two-range subtransmission, and shaft final drive. The ’81 CB900F addendum lists 902 cc and 8.8:1 compression with a five-speed constant-mesh transmission and chain drive. Its model-specific pages revise dimensions, engine data, carburetion, drivetrain, electrical specifications, torque values, cable and harness routing, lubrication, valve adjustment, engine removal, crankcase work, front and rear suspension, hydraulic brakes, and the wiring diagram.

For system-opening repair work, follow Honda’s component-specific safety notes. Brake fluid must be kept off painted surfaces, and the manual calls for battery-ground disconnection during applicable engine and electrical service.

Repair and Diagnostic Coverage

The shop manual goes well beyond routine maintenance. Factory procedures include engine removal and installation; camshaft and cylinder-head service; valve-guide replacement and valve-seat refacing; cylinder and piston measurement; oil-pump inspection; clutch and starter-clutch service; gearshift-linkage repair; subtransmission disassembly and setup; crankcase and crankshaft/primary-shaft work; front and rear suspension service; final-drive backlash and tooth-contact inspection; hydraulic-brake service; and charging, ignition, starter, and switch-circuit testing.

Fuel-system coverage includes the four-carburetor bank, vacuum-cylinder inspection, pilot screws, floats and jets, air-cutoff valves, accelerator-pump components, float-level setting, carburetor separation, synchronization, fast-idle adjustment, and the pilot-screw idle-drop procedure. Electrical material covers the battery/charging system, A.C. generator, regulator/rectifier, spark units, pulser generator, electric starter, switch continuity, and the rear-suspension air-pressure warning circuit.

Representative factory values include:

• Engine oil: 3.5 L (3.7 US qt) at an oil change; 4.5 L (4.7 US qt) after engine disassembly.
• Cold valve clearance: 0.06–0.13 mm (0.002–0.005 in), intake and exhaust.
• Spark plug gap: 0.6–0.7 mm (0.024–0.028 in).
• Engine oil pressure: 5.5 kg/cm² (78 psi) at 7,000 rpm with oil at 80°C/176°F.
• CB900C dual-range subtransmission: 0.638 high range and 0.721 low range; 0.6 L (0.61 US qt) SAE 80 hypoid gear oil.
• CB900C final-drive oil: 150 cc (5.1 oz), API GL-5 hypoid; SAE 90 above 5°C/41°F or SAE 80 below that temperature.

Honda also identifies dedicated service tools rather than leaving critical repair setups to improvised methods. Examples include valve lifter holder 07964-4220001, primary gear holder 07924-4250000, clutch center holder 07923-3710000, oil-pressure gauge attachment 07510-4220100, subtransmission damper compressor 07964-4610000, and preload inspection tool 07908-4610000. Some subtransmission tools are specifically marked as unavailable in the U.S.A., useful information when planning that repair.

The visual reference material includes the Cable & Harness Routing views, Engine Lubrication Diagram, Valve Shim Selection Chart, Dual Range Subtransmission power-flow illustration, Shaft Drive layout, and the ’81 CB900F Wiring Diagram. These drawings support component identification, routing checks, measurement work, and electrical fault tracing without substituting generic service information for model-specific data.

Several cautions are specific to this engine and carburetor layout. Valve-shim service has an interference warning: incorrect valve-lifter-holder positioning or crankshaft rotation can make intake and exhaust valves strike and damage each other. The carburetor pilot-screw seat can be damaged if the screw is tightened against the seat. When separating the carburetor bank, Honda specifies horizontal separation to avoid damaging the joint pipes and choke linkage.

Important PDF Scope

The original Honda contents page lists a base Section 12 – Transmission, a standalone Section 23 – Troubleshooting, an ’81 CB900C Addendum, and an ’82 CB900C·F Addendum. Those listed sections are not contained in this 367-page PDF. The included model addendum is the ’81 CB900F Addendum; section-level troubleshooting remains present throughout many of the included chapters.

The final two PDF pages are a separate Dynojet 1127.002 Stage 1 & 3 jet-kit instruction sheet for 1980–82 U.S. CB750/CB900 models. They are appended reference material and are not Honda service-publication pages.