Honda ST50/ST70 & CT70/CT70H Shop Manual Set, 1969–1982

The CT70 addenda supplement the base shop manual with production changes, revised service data and procedures for the affected assemblies. Later sections refer back to earlier procedures where those instructions still apply.

Companion manual required: The base publication is intended for use with the separate 50/65 Shop Manual, Code No. 620401. That manual is not included. References to it cover shared engine and carburetor information, plus the separate Periodic Adjustment and Trouble Shooting chapters.

PDF Search, Bookmarks and Diagram Detail

Search and diagram readability: Text search works across many repair sections, but parts of the tables and wiring diagrams are not searchable. Embedded bookmarks provide access to the base chapters and individual CT70 addenda. Small wiring labels need zooming; some fine lettering remains soft.

Supplied as one printable, English-language PDF with 130 pages total. The total includes all publications listed above, one additional cover page and one intentionally blank page.

Engine, Chassis and Electrical Service

These selected contents outline the main repair areas rather than reproduce the full contents list. Additional topics include side-stand inspection and spark-arrester servicing.

• Engine repair: Step-by-step removal and installation, cylinder-head disassembly, valve-guide replacement, oil-pump inspection, crankshaft checks and cam-chain tensioner service.

• Clutch and transmission: Separate clutch assemblies and gear-position diagrams, friction-disc inspection, shift-fork and drum measurements, transmission reassembly and kick-starter assembly instructions.

• Carburetor service: Keihin piston-valve carburetor diagrams, jetting tables, later overhaul procedures, float-level checks, pilot-screw adjustment and high-altitude settings.

• Chassis repair: Steering-head bearings, wheel hubs, drum brakes, swingarm bushings, suspension disassembly and component inspection.

• Electrical diagnosis: Generator charging tests, ignition-coil resistance and performance checks, condenser testing, rectifier checks, switch-continuity charts and model-specific wiring diagrams.

This material suits mechanics familiar with standard workshop practice and equipped for engine measurement and electrical testing; it does not teach basic workshop procedures.

Clutch Variants and CT70 Production Changes

The H/HK1 sections distinguish the manual clutch and four-speed transmission from the centrifugal-clutch arrangement used on the standard CT70. Separate clutch assembly views and transmission gear-position drawings support internal inspection and reassembly.

For restoration and routine servicing, the model-specific sections help match factory inspection data and assembly information to the hardware being worked on. The later addenda identify changes that would be missed by relying on the base manual alone.

The K6 supplement starts at frame number CT70-2600008. The K7 supplement starts at CT70-2700005 and applies to machines manufactured before February 1978.

US emissions equipment: The 1979 addendum addresses machines manufactured after December 31, 1977. It describes the factory-set carburetor and closed crankcase-breather system. A flow diagram and exploded breather-separator view show the relationship between the intake, separator and storage tank.

Keihin Carburetor Revisions

The later fuel-system sections distinguish the PB36A carburetor for 1978, PB37B for 1980 and PB16A for 1982. Their specifications and adjustment instructions should be read with the corresponding addendum.

The 1982 section adds fuel-strainer servicing and passage and jet cleaning. High-altitude instructions identify the applicable main jets and the changes required when returning to lower elevations.

The US pilot-screw instructions address the limiter cap and warn that forcing it off can break the screw.

Suspension and Later Engine Updates

The 1980 addendum provides step-by-step procedures for the revised oil-filled front forks, including oil-seal replacement, fork-tube runout inspection and reassembly. Rear-shock service includes spring inspection and assembly details. Fork-service cautions explain how improper clamping can damage the sliding surfaces.

The 1981 material covers vehicle-identification locations, battery ventilation and harness routing.

For 1982 engine work, the addendum shows oil-pump drive engagement, cylinder-head and valve assembly, camshaft inspection limits and piston-ring installation details.

Electrical Tests, Wear Limits and Service Tools

Electrical reference material includes 6V bulb specifications, flywheel-magneto test data and ignition-coil performance checks. The CT70H US and CT70 ’82 wiring diagrams include wire-color keys and switch-connection information. CT70 ’80 cable-routing views show control-cable and harness paths.

Engine inspection tables cover valve-seat dimensions, piston-ring clearances, crankshaft runout and connecting-rod bearing play. The Tightening Torque Limits table covers major engine fasteners; chassis tightening specifications accompany the relevant procedures.

Tool lists identify equipment such as flywheel puller 07933-0010000 and clutch outer holder 07923-0400000.

Always verify standard wear limits and use the correct torque specifications before reassembling critical engine components.

Selected Valve, Float-Level and Ring Inspection Data

The 1982 CT70 specifications give intake and exhaust valve clearance as 0.05 mm (0.002 in), measured cold. Its piston-ring inspection section lists a 0.5 mm (0.02 in) service limit for the top and second ring end gaps.

For the 1980 PB37B carburetor, the float-level specification is 10.7 ± 1 mm (0.42 ± 0.04 in). The associated inspection instructions specify light contact between the float arm and float valve during measurement.