Honda C65/C65M/S65 & 50/70 Series Factory Service Manual Set

Honda notes that the supplement uses the 50/65 material for detailed fundamentals, so the base repair information and model-specific supplement are together in this file.

Text Search, Page Bookmarks and Wiring Detail

Search and diagram viewing: PDF text search is not available. Embedded page bookmarks use filenames rather than descriptive chapter titles. Wiring diagrams are sideways, and their small labels require rotation and zooming for comfortable reading.

ZIP download containing one printable, 156-page PDF in English. The total includes one foreword page, four contents pages and three memo pages.

Engine Overhaul, Carburetor Service and Electrical Diagnosis

These are selected contents, rather than a complete table of contents; further topics include air-cleaner servicing and muffler maintenance.

• Engine repair: Step-by-step engine removal and installation, cylinder-head disassembly, valve work, cylinder and piston inspection, and crankshaft service.

• Clutch and transmission: Clutch disassembly and inspection, transmission and shift-mechanism repair, kick starter service, and model-specific adjustment procedures.

• Fuel system: Carburetor cleaning, fuel-level measurement, mixture adjustment and setting tables, with troubleshooting for overflow, poor idling and acceleration problems.

• Wheels and suspension: Wheel removal, brake inspection, steering service, front and rear cushion work, rear-fork inspection, and drive-chain adjustment.

• Electrical troubleshooting: Starter-circuit diagnosis, ignition-coil and charging checks, battery service, spark-plug diagnosis, lighting and horn faults, and selenium-rectifier testing.

• Wiring and test references: Model-specific wiring diagrams, generator performance charts, service limits and component-specific tightening tables.

The repair sections suit mechanics and experienced owners equipped to use micrometers, dial gauges and electrical test equipment; internal repairs also call for the specified special tools.

Engine Construction and Internal Repair

Engine variants: Specifications distinguish the 49 cc C50/C50M/S50/C50MK1 engines, 63 cc C65/C65M/S65 engines and 72 cc CL70/C70/C70M engines. The base lubrication-capacity table lists 0.8 L, while C50MK1 and the 70-series specifications list 0.7 L.

Cylinder head and timing: Valve work extends to seat-contact inspection, seat cutting and lapping, and valve-guide replacement. Camshaft, cylinder, piston and piston-ring measurements are accompanied by service limits. The Cam Chain Tensioner Detail Diagram explains the oil-damped mechanism; the supplement adds check-valve inspection.

Lubrication: The Pressure Lubrication Diagram and Oil Pump Theory of Operation view accompany trochoid-pump inspection, oil-route explanations, and coverage of the screen and centrifugal filter.

Piston reassembly notes address crown-arrow orientation, piston-pin clip positioning and clip tension. The right-crankcase-cover instructions flag gasket damage and misalignment.

Clutch Variants and Carburetor Settings

The base specifications distinguish the automatic centrifugal clutches on C50/C50M/C65/C65M from the wet multi-disc units on S50/S65 and C50MK1. The supplement separates CL70’s conventional wet clutch from the automatic centrifugal version used on C70/C70M.

Transmission inspection covers shaft and gear clearances, shift-fork wear and engagement checks. The supplement’s tightening table distinguishes the clutch nut, CL70/C70 flywheel and C70M rotor.

Carburetion: Carburetor Cross Section Diagrams separate the C50/C50M/C65/C65M group from S50/S65. Model-specific setting tables record carburetor type, throttle and venturi bore, main and air jets, needle and slow-jet calibration, pilot-circuit data, valve seat and fuel-level height.

This is particularly relevant when a motorcycle has acquired mismatched jets or carburetor parts during previous repair work. The supplement supplies its own settings and refers back to the base manual for adjustment fundamentals.

Chassis Inspection and Suspension Differences

The manual distinguishes the S50/S65 pressed-sheet-steel frame and bottom-link front/swing-arm rear suspension from CL70’s T-bone frame and telescopic fork, and the C70/C70M backbone frame with bottom-link front suspension.

Wheel and axle inspection includes dial-gauge runout and bend limits. Internal-expanding brakes have shoe, drum and lining inspection data.

Front-damper limitation: The base front-cushion section cautions against dismantling the damper bottom metal because special tools are required and its component parts are not sold individually.

Brake, wheel, fuel-system, and live electrical work directly affect roadworthiness and safety; use the stated wear limits, tightening values, and test conditions before returning the motorcycle to service.

Starting, Charging and Fault Diagnosis

Electrical coverage includes starting-system troubleshooting for C50M/C65M and starter-motor inspection for C70M. The A.C. Generator Performance Chart supports charging checks, alongside ignition-coil tests, spark-advancer data and battery troubleshooting.

Engine and carburetor fault tables connect symptoms such as hard starting, warm-engine malfunction, poor throttle response and abnormal noise with probable causes and corrective work. Compression testing is linked to valve adjustment, head-gasket condition and piston-ring inspection.

Wiring diagrams cover C50/C65, C50M/C65M, S50/S65, CL70, C70 and C70M. Separate C70M drawings distinguish General Export and U.S.A. Type circuits.

The selenium-rectifier cautions explain how wafer damage or disturbed moisture sealing shortens component life, and how operation with the battery or electrical load disconnected can puncture the rectifier.

Honda Special-Tool References

Honda Tool Set No. 07900-1180000 is specified for C65/S65 and carried over to the CL70/C70/C70M supplement.

Individual references include tappet wrench set 07908-0010000 and clutch assembly tool 07960-0110000. Flywheel work uses holder 07925-0010000 and puller 07933-0010000; rear-cushion disassembly tool 07959-3290000 is also identified.

A Preview of Wear Limits and Electrical Test Values

Friction components: The base clutch section lists friction-disc thickness at 3.5 mm, with replacement below 3.1 mm. Its rear-wheel section gives a 3.5 mm standard brake-lining thickness and replacement below 1.5 mm.

Valve adjustment: For C50/C50M/C65/C65M/S50/S65, intake and exhaust tappet clearance is 0.05 mm (0.002 in.), measured with the engine cold.

Rectifier testing: The CL70/C70/C70M supplement specifies forward resistance below 15 ohms and reverse resistance above 1,500 ohms for each selenium-rectifier element.