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

Clymer’s Honda 400–450cc Twins Service Manual, P/N M334, Fifth Edition, Twelfth Printing, covers the listed 1978–1987 models in 12 technical chapters, with quick-reference data, an index, and model-specific wiring diagrams.

PDF Navigation and File Contents

Search, bookmarks and wiring detail: PDF text search is unavailable. Embedded bookmarks mostly use image/file names rather than chapter titles. Small wiring labels require zooming, and some wire-color abbreviations remain blurred. Printed page 80 is missing; printed page 1 appears before the title pages.

Supplied as a ZIP archive containing one printable PDF with 439 pages, including 14 cover and preliminary pages.

Engine, Transmission and Chassis Service

These selected repair topics represent part of the manual’s contents. Other subjects include frame stripping and repainting, plus centerstand and sidestand service.

• Maintenance and troubleshooting: Scheduled lubrication, tune-up, compression checks, and diagnosis of starting problems, poor running, engine noises, lubrication faults, and shifting complaints.

• Engine repair: Step-by-step removal and in-frame service, cylinder-head and valve work, cam-chain and balancer systems, pistons, crankshaft, connecting rods, oil pump, alternator, starter gears, and kickstarters.

• Clutch and transmissions: Wet multi-plate clutch repair, external and internal shift mechanisms, 5-speed and 6-speed manual gearboxes, and torque-converter automatic transmission service.

• Fuel and exhaust: Keihin constant-velocity carburetor removal, cleaning, inspection, reassembly, adjustment, and synchronization, plus cables, fuel delivery, crankcase breathing, emission controls, and exhaust service.

• Electrical diagnosis: Charging, CDI ignition, starter, lighting, switch, instrument, and fuse checks, supported by component test illustrations and model-specific wiring schematics.

• Wheels and suspension: Wheel, hub, tire, steering-head, front-fork, drive-chain, shock-absorber, and swingarm inspection and service, with separate procedures where construction differs.

• Brakes: Drum- and disc-brake service, master-cylinder and caliper rebuilding, brake-hose replacement, system draining, and bleeding procedures.

The manual suits owners who are reasonably handy with tools, while advising a careful assessment of ability and equipment before major engine disassembly.

Model and Transmission Differences

Coverage includes 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 includes CB450T (1982), CB450SC Nighthawk (1982–1983 and 1985–1986), CM450A (1982–1983), CM450C (1982), CM450E (1982–1983), and CMX450C Rebel (1986–1987).

The transmission illustrations distinguish mainshaft and countershaft assemblies, shift drums, forks, and Rebel-specific locking hardware. Manual gearbox access requires engine removal and crankcase separation. The clutch section also explains the change from early rubber dampers to later damping springs.

Chapter Six treats the A-model automatic transmission separately, including its shafts, gears, shift mechanism, oil cooler, and converter-related components. The torque-converter housing is a sealed assembly: service covers removal, installation, and associated gears and springs rather than internal converter rebuilding.

These construction differences help match parts and repair procedures to the particular model before disassembly.

Cylinder Heads, Balancers and Engine Assembly

The engine section describes the air-cooled SOHC parallel twin, its three-valve cylinder heads, chain-driven camshaft, and twin counterbalancers. Separate cylinder-head, camshaft, and rocker-arm procedures distinguish 1978–1981 engines from 1982-on versions.

Early cylinder-head coverage: The 1978–1981 reassembly sequence is incomplete because printed page 80 is absent.

Lower-engine coverage includes crankcase separation, bearing-clearance inspection, crankshaft and connecting-rod service, and balancer alignment. The later engine oil-cooler arrangement applies from 1982 except on the Rebel 450.

The timing cautions explain how incorrect camshaft, sprocket, and flywheel indexing can damage the engine. Gasket notes address oil leaks caused by inappropriate sealer and engine damage from incorrect gasket thickness.

Carburetors and Emission Equipment

The fuel chapter distinguishes carburetors with accelerator pumps and provides separate Rebel carburetor illustrations. Float-level checks, pilot-screw adjustment, synchronization, and idle adjustment sit alongside fuel-shutoff valve, tank, filter, throttle-cable, and choke-cable service.

Crankcase-breather coverage applies to 1986-on U.S. models. Evaporative-emission service applies to 1985-on California models; the exhaust-emission section covers the secondary-air system on the 1986 CB450SC California version.

Charging, Ignition and Starting Diagnosis

Electrical tests distinguish early 400cc machines, later 450cc models, and the Rebel 450. Alternator stator, ignition pulser, regulator/rectifier, ignition-coil, starter-motor, and starter-solenoid checks are organized by the applicable system and model group.

CDI testing limits: The Rebel procedure checks the surrounding ignition components to isolate a suspected CDI fault. Other models are referred for dealer testing; ignition-coil resistance specifications are provided for 450cc models rather than the 400cc group.

Separate wiring diagrams include CB400T Type I, CB400A, CM400A, CB450SC Nighthawk, CM450E, and CMX450C Rebel configurations.

Brake, Fork and Wheel Construction

Chassis sections distinguish drum-brake, single-piston disc, dual-piston disc, and Rebel front-wheel layouts. Steering-head procedures separate loose and assembled ball bearings; fork instructions distinguish air-assist and non-air-assist designs.

Wheel and hub coverage separates early spoke wheels, ComStar and ComCast wheels, and Rebel-specific assemblies. Rear-suspension instructions include spring removal, shock inspection, and swingarm bushings or bearings. Sealed hydraulic damper units are replaced rather than rebuilt.

Workshop Tables and Special Tools

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

Individual system chapters add inspection dimensions, wear limits, clearances, electrical test values, and assembly specifications in metric and U.S. units.

The alternator section specifies Honda flywheel puller 07933-3950000, or an equivalent, and warns that removal without a puller can damage the crankshaft or rotor. A separate valve-guide service table lists model-dependent reamers and Honda part numbers. Exploded views support engine, clutch, gearbox, torque-converter, carburetor, hub, fork, and caliper work.

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.

Examples of Piston-Ring Inspection Limits

For the 400cc engines, the piston inspection table lists a standard top- and second-ring end gap of 0.2–0.4 mm and a wear limit of 0.60 mm.

The corresponding 450cc figures are 0.1–0.3 mm standard and 0.50 mm at the wear limit. These specifications accompany ring inspection and are separate from the oil-control rail clearances.