1978–1987 Honda 400, 450 Twins Service Manual (P/N M334, Clymer)

• Clymer publication M334, Fifth Edition, Twelfth Printing, covering the listed Honda 400–450cc twins from 1978–1987 in 12 technical chapters, with front quick-reference pages, an index, and model-specific wiring diagrams.
• Covers engine removal and in-frame repair, cylinder-head and camshaft service, valve work, cam-chain and balancer systems, pistons, crankshaft and connecting rods, oil pump, alternator, starter gears, and manual- or automatic-model kickstarter assemblies.
• Details wet multi-plate clutch repair, external and internal shift mechanisms, model-specific 5-speed and 6-speed manual transmissions, plus the two-speed torque-converter automatic transmission used on the A models.
• Includes Keihin constant-velocity carburetor removal, cleaning, inspection, reassembly, adjustment, and synchronization, along with throttle and choke cables, fuel shutoff valve, tank, filter, crankcase breathing, emission-control equipment, and exhaust service.
• Provides charging, CDI ignition, starter, lighting, switch, instrument, and fuse testing, with alternator, regulator/rectifier, ignition-coil, and starter-solenoid checks supported by model-specific wiring schematics.
• Covers drum- and disc-brake repair, master-cylinder and caliper rebuilding, brake-hose replacement and bleeding, plus wheel, hub, tire, steering-head, front-fork, rear-suspension, drive-chain, shock-absorber, and swingarm procedures.

Model and Configuration Coverage

This PDF covers the CB400T Type I and Type II (1978–1979), CB400T (1980–1981), CB400A (1978), CM400T and CM400A (1979–1981), CM400E (1980–1981), and CM400C (1981). The later group covers the CB450T (1982), CB450SC Nighthawk (1982–1983 and 1985–1986), CM450A (1982–1983), CM450C (1982), CM450E (1982–1983), and CMX450C Rebel (1986–1987).

Transmission coverage is configuration-specific rather than generic. The 5-speed section is assigned to the CB400T Type I, CB400T Type II, CM400T, CM400C, and CM400E. Separate 6-speed procedures cover the remaining manual-transmission models and identify Rebel 450 construction differences. Chapter Six is reserved for the two-speed torque-converter automatic used on the 1978 CB400A, 1979–1981 CM400A, and 1982–1983 CM450A, including the converter, transmission shafts and gears, internal shift mechanism, gearshift drum and fork, and oil cooler.

Technical Breakdown and Workshop Application

The engine chapters go well beyond routine tune-up work. They describe the air-cooled SOHC parallel twin, its three-valve-per-cylinder cylinder head, chain-driven camshaft, and twin counterbalancers, then carry that layout through removal, disassembly, inspection, measurement, repair, and reassembly. Separate cylinder-head, camshaft, and rocker-arm procedures distinguish 1978–1981 engines from 1982-on versions. The manual also identifies the later oil-cooler arrangement, which applies from 1982 except on the Rebel 450, and explains the change from early clutch rubber dampers to later damping springs.

Fuel-system coverage accounts for the accelerator-pump carburetors used on later models and places synchronization and idle adjustment in the proper tune-up context. Electrical diagnosis is divided by system and model group, including different stator, pulser, charging, and regulator/rectifier tests for early 400cc machines, later 450cc machines, and the Rebel 450.

Chassis chapters likewise separate drum-brake, single-piston disc, dual-piston disc, and Rebel front-wheel layouts; loose- and assembled-ball steering heads; air-assist and non-air-assist forks; early spoke hubs; later ComStar and ComCast wheels; and Rebel-specific wheel and hub service.

The variant notes matter during parts selection and assembly. Rebel 450 transmission illustrations identify additional locking hardware, while its fork, hub, brake, and electrical procedures are kept separate where the construction differs. California-model coverage is also clearly limited: evaporative-emission service applies to 1985-on California models, and the exhaust-emission section is specific to the 1986 CB450SC California version.

Several repair traps are called out directly. Incorrect camshaft, cam-sprocket, and flywheel indexing can cause expensive engine damage. The alternator rotor must be removed with the specified puller rather than pried from the crankshaft. The manual also warns against adding sealer to specified engine gaskets because it prevents the material from swelling as intended and can cause leaks; incorrect gasket thickness can damage the engine.

Key Specifications and Reference Data

The front Quick Reference Data pages condense frequently used specifications and capacities. Chapter Three then ends with eight maintenance and tune-up tables covering the scheduled service program, tire pressures, battery state of charge, maintenance torque data, engine-oil and fork-oil capacities, drive-chain replacement numbers, and tune-up specifications.

The engine, clutch, manual transmission, automatic transmission, carburetor, electrical, suspension, brake, and frame chapters add their own torque tables, inspection dimensions, wear limits, clearances, test values, and assembly specifications in both metric and U.S. units.

The tool references are specific. The engine section identifies Honda flywheel puller 07933-3950000, or an equivalent, for alternator-rotor removal. A dedicated table also lists model-dependent valve-guide reamers and their Honda part numbers.

The wiring section supplies separate schematics for configurations such as the 1978–1979 CB400T Type I, 1978 CB400A, 1979–1981 CM400A, 1982–1983 CB450SC Nighthawk, 1982–1983 CM450E, and 1986–1987 CMX450C Rebel. Exploded views and numbered component drawings cover the engine, clutch, 5-speed and 6-speed gearsets, torque converter, carburetors, wheel hubs, forks, and brake calipers.

Before beginning repair work, follow the manual’s safety notes and its support, fuel-handling, brake-fluid, and electrical-isolation precautions. The procedures involve a supported motorcycle, spring-loaded suspension parts, rotating engine components, and high-current electrical testing.