1969–1976 Honda ST50 / ST70 / CT70 Factory Shop Manual

This shop manual covers the 1969–1976 Honda ST50, ST70, and CT70, with Honda Motor Co., Ltd.'s 1970 documentation for the four-stroke O.H.C. engine platform, chassis, and electrical systems.

Supplied as a single 49-page PDF in English.

• Engine repair: Engine removal and installation, cylinder-head disassembly, valve-seat repair, valve-guide replacement, and piston and crankshaft inspection.

• Lubrication and timing: Trochoid oil-pump disassembly and clearance checks, oil-flow routing diagrams, valve timing, and cam-chain tensioner inspection.

• Drivetrain: Centrifugal-clutch adjustment, transmission inspection, gear-shift mechanism service, and kick-starter construction and assembly references.

• Fuel and air intake: Keihin carburetor cross-section views, model-specific carburetor specifications, and oiled foam air-cleaner service.

• Chassis and brakes: Steering, front and rear cushion service, wheel and bearing inspection, and internal expanding shoe brake repair.

• Electrical diagnosis: Ignition-coil and selenium-rectifier testing, generator performance specifications, and four wiring diagrams with switch-connection tables.

Written for service shops, this manual suits mechanics familiar with engine disassembly, micrometers, dial gauges, and specialist service tools.

Engine Repair and Lubrication

Engine removal and installation include the CT70's engine and crankcase protectors. Cylinder-head repair extends to valve-seat cutting and lapping, valve-guide replacement and reaming, and valve-spring and camshaft inspection.

The piston, cylinder, and crankshaft inspection sections pair measurement procedures with standard dimensions and service limits. These references help you assess measured wear before deciding which engine parts can be reused.

Oil-flow routing diagrams trace lubrication through the trochoid pump and centrifugal filter. An exploded oil-pump view supports component identification, while the cam-chain tensioner section covers its hydraulic and spring operation and check-valve inspection.

The engine-fastener torque table covers the crankcases, cylinder head, clutch, flywheel, and other mounting points. Special-tool references include flywheel puller 07011-09801 and valve-guide reamer 07008-25002.

Clutch, Transmission, and Kick Starter

The 3-speed constant mesh transmission is illustrated in neutral and each forward gear. Inspection sections cover gear backlash, shaft clearances, gear shift forks, and gear shift drum wear.

Clutch repair includes friction-disc and spring checks, with separate spring specifications for ST50 and ST70/CT70. The kick starter pinion drawing shows its relationship to the countershaft low gear and identifies the spring and retaining components.

Keihin Carburetor and Air Cleaner

Carburetor cross-section views accompany model-specific jetting, needle, and fuel-level specifications. For further carburetor information, the text refers to the separate Honda 50/65 Shop Manual, which is not included in this PDF.

Air-cleaner coverage describes the oiled foam element and its cleaning and servicing. When servicing the fuel system, maintain a well-ventilated workspace and follow standard shop safety practices.

Steering, Suspension, Wheels, and Brakes

Frame documentation covers the folding steering handle, steering stem, front and rear fork assemblies, and wheel hub construction with 63010 ball bearings. Brake inspection includes drum, shoe, and lining wear checks, with control adjustment and reassembly information.

The front and rear cushion sections distinguish spring-only front units from hydraulically damped rear units. Disassembly notes warn that improper clamping or handling can damage the front cushion's aluminum upper holder and rubber-coated piston.

Drive-chain maintenance includes rear-wheel alignment checks; the manual explains that mismatched chain-adjuster positions affect steering.

Ignition, Charging, and Wiring Diagrams

The 6V electrical section gives separate daytime and nighttime charging-performance data. Ignition-coil resistance checks and selenium-rectifier tests support diagnosis of weak spark and charging faults; the rectifier section also distinguishes a basic service-tester check from specialist electrical testing.

Four wiring diagrams cover ST50 U.K. Type, ST70-I and ST70-II General Export Types, and CT70 U.S.A. Type. Wire-color keys and main-switch or combination-switch switching diagrams identify the connections for each configuration.

PDF Navigation and Wiring Readability

The total includes 48 manual pages and one added UserFriendlyCDs cover, with all four wiring pages and the index already counted. Chapter and subsection bookmarks are included; manual text search is unavailable. Small wiring-diagram labels require zooming.