1976-1992 Honda CG125 Service & Repair Manual

Honda CG125 Owners Workshop Manual by Pete Shoemark with an additional Chapter on the 1985 on models by Jeremy Churchill Models covered CG125. 124cc. June 1976 to May 1978 CG125K1. 124cc. May 1978 to March 1981 CG125-B. 124cc. March 1981 to March 1982 CG125-C. 124cc. March 1982 to November 1984 CG125-E. 124cc. November 1984 to April 1985 CG125(BR)-E/F. 124cc. April 1985 to April 1988 CG125(BR)-J. 124cc. April 1988 to September 1991 CG125(BR)-K. 124cc. September 1991 on ISBN 1 85010 918 4 © Haynes Publishing 1994 All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage or retrieval system, without permission in writing from the copyright holder. Printed in the USA (433-4T9) Haynes Publishing Sparkford Nr Yeovil Somerset BA22 7JJ England Haynes Publications, Inc 861 Lawrence Drive Newbury Park California 91320 USA British Library CataloGuing in Publication Data A catalogue record for this book is available from the British Library ~

Acknowledgements Our thanks are due to APS Motorcycles of Wells (formerly Fran Ridewood & Co), Paul Branson Motorcycles of Yeovil, and CSM of Taunton, who supplied the machines featured in this manual. We would also like to thank the Avon Rubber Company, who kindly supplied information and technical assistance on tyre fitting; NGK Spark Plugs (UK) Ltd for information on spark plug maintenance and electrode conditions and Renold Limited for advice on chain care and renewal. About this manual The author of this manual has the conviction that the only way in which a meaningful and easy to follow text can be written is first to do the work himself, under conditions similar to those found in the average household. As a result, the hands seen in the photographs are those of the author. Even the machines are not new: examples that have covered a consider- able mileage were selected so that the conditions encountered would be typical of those found by the average owner. Unless specially mentioned, and therefore considered essential, Honda service tools have not been used. There is invariably some alternative means of slackening or removing some vital component when service tools are not available and risk of damage has to be avoided at all costs. Each of the six Chapters is divided into numbered Sections. Within the Sections are numbered paragraphs. In consequence, cross reference throughout this manual is both straightforward and logical. When a reference is made 'See Section 5.12' it means Section 5, paragraph 12 in the same Chapter. If another Chapter were meant, the text would read 'See Chapter 2, Section 5.12'. All photographs are captioned with a Section/paragraph number to which they refer and are always relevant to the Chapter text adjacent. Figure numbers (usually line illustrations) appear in numerical order, within a given Chapter. Fig. 1.1 therefore refers to the first figure in Chapter 1. Left-hand and right-hand descriptions of the machines and their component parts refer to the right and left of a given machine when the rider is seated normally. Motorcycle manufacturers continually make changes to specifications and recommendations, and these, when notified, are incorporated into our manuals at the earliest opportunity. We take great pride in the accuracy of information given in this manual, but motorcycle manufacturers make alterations and design changes during the production run of a particular motorcycle of which they do not inform us. No liability can be accepted by the authors or publishers for loss, damage or injury caused by any errors in, or omissions from, the information given.

Contents Acknowledgements About this manual Introduction to the Honda CG125 Model dimensions and weight Ordering spare parts Safety first! Routine maintenance Quick glance maintenance adjustments and capacities Recommended lubricants Working conditions and tools Chapter 1 Engine, clutch and gearbox Chapter 2 Fuel system and lubrication Chapter 3 Ignition system Chapter 4 Frame and forks Chapter 5 Wheels, brakes and tyres Chapter 6 Electrical system Chapter 7 The 1985 on models Wiring diagrams Conversion factors Index Page 2 2 5 5 6 7 8 13 13 / 15 52 60 67 80 93 107 103, 124 125 126 I

The Honda CG125 model The Honda CG125-C model

Introduction to the Honda CG125 The CG125 model first appeared in the UK in June 1976. It can be regarded in many ways as a utility version of the popular CB1 25 with which it shares many features. The basic difference between the two models is the CG125's use of pushrod operated overhead valves in place of the more popular overhead camshaft arrangement. The unit provides surprisingly brisk performance coupled with good fuel economy. The machine in general is functional and sensibly equipped, and does not suffer the surfeit of gadgetry so often found on its contemporaries. Its inherent simplicity makes it an ideal learner's or commuter's mount, both in terms of ease of riding and in its ease of maintenance. A noteworthy feature is the adoption of a full rear chain enclosure. Although this is by no means a new idea, having appeared and disappeared many times over the years with the changing dictates of fashion, it is, nevertheless, an eminently sensible feature, greatly extending chain life. Despite remaining basically unchanged, the CG125 has received several modifications and has been altered slightly in appearance to keep up with its rivals. Five distinct versions have appeared, with differences of varying significance, which are identified (where applicable) in this Manual by their Honda model code suffixes. Identification details, as available, are given below with the approximate dates of import; note that the latter need not necessarily coincide with the machine's date of registration. The CG125 model (no identifying suffix) has the frame numbers CG125-1023061 to 1111090. Engine numbers are not available. Identified by its shrouded, external spring, front forks, this model Was imported from June 1976 to May 1978. The CG125K1 model has the frame numbers CG125-1114636 to 1162518. Engine numbers not available. It differed most noticeably from the CG125 model in having front forks with internal springs and exposed stanchions, and was imported from May 1978 to March 1981. The CG125-B model has the frame numbers CG125-1202755 to 1223689; its engine numbers start at CG125E-1374586. It can be distinguished from the K1 model only by its different paintwork and graphics and was imported from March 1981 to March 1982. The CG125-C model has the frame numbers CG125-1272831 to 1286692; its engine numbers start at CG125E-1513928 on. Fitted with revised tail lamp, flashing indicator lamps, handlebar switches and the usual detail changes to paintwork and graphics. This model is also fitted with a higher compression engine and the (T)PFC carburettor for greater fuel economy. Note also that the ignition switch is combined in a new warning lamp cluster, mounted next to the speedometer. Imported from March 1982 to November 1984. The CG125-E model has the frame number CG 125-1288790 to 1293380 and the engine numbers CG125E-1689761 to 1694851. Identical to the C model except for detail changes to the graphics, this model was imported from November 1984 to April 1985. All the aforementioned models are of Japanese manufacture and are covered in Chapters 1 to 6. Later models were manufactured in Brazil and known as the CG125(BR) models; refer to Chapter 7 for further information. Model dimensions and weight Overall length Overall width Overall height Wheelbase Seat height Ground clearance Dry weight 1840 m m (72.4 in) 735 m m (28.9 in) 1025 mm (40.4 in) 1200 m m (47.2 in) 755 m m (29.7 in) 135 m m (5.3 in) 95 kg (209 Ib)

Ordering spare parts * When ordering spare parts for the CG125 models, it is advisable to deal direct with an official Honda agent, who will be able to supply many of the items required ex-stock. It is advisable to get acquainted with the local Honda agent, and to rely on his advice when purchasing spares. He is in a better position to specify exactly the parts required and to identify the relevant spare part numbers so that there is less chance of the wrong part being supplied by the manufacturer due to a vague or incomplete description. When ordering spares, always quote the frame and engine numbers in full, together with any prefixes or suffixes in the form of letters. The frame number is found stamped on the right-hand side of the steering head, in line with the forks. The engine number is stamped on the left-hand side of the crankcase, immediately behind the oil strainer cap. Use only parts of genuine Honda manufacture. A few pattern parts are available, sometimes at a cheaper price, but there is no guarantee that they will give such good service as the originals they replace. Retain any worn or broken parts until the replacements have been obtained; they are sometimes needed as a pattern to help identify the correct replacement when design changes have been made during a production run. Some of the more expendable parts such as spark plugs, bulbs, tyres, oils and greases etc., can be obtained from accessory shops and motor factors, who have convenient opening hours and can often be found not far from home. It is also possible to obtain them on a Mail Order basis from a number of specialists who advertise regularly in the motorcycle magazines. Frame number location Engine number location

Safety first! Professional motor mechanics are trained in safe working procedures. However enthusiastic you may be about getting on with the job in hand, do take the time to ensure that your safety is not put at risk. A moments lack of attention can result in an accident, as can failure to observe certain elementary precautions. There will always be new ways of having accidents, and the following points do not pretend to be a comprehensive list of all dangers; they are intended rather to make you aware of the risks and to encourage a safety-conscious approach to all work you carry out on your vehicle. Essential DOs and DON'Ts DON'T start the engine without first ascertaining that the transmission is in neutral. DON'T suddenly remove the filler cap from a hot cooling system - cover it with a cloth and release the pressure gradually first, or you may get scalded by escaping coolant. DON'T attempt to drain oil until you are sure it has cooled sufficiently to avoid scalding you. DON'T grasp any part of the engine, exhaust or silencer without first ascertaining that it is sufficiently cool to avoid burning you. DON'T allow brake fluid or antifreeze to contact the machine's paintwork or plastic components. DON'T syphon toxic liquids such as fuel, brake fluid or antifreeze by mouth, or allow them to remain on your skin. DON'T inhale dust - it may be injurious to health (see Asbestos heading). DON'T allow any spilt oil or grease to remain on the floor — wipe it up straight away, before someone slips on it. DON'T use ill-fitting spanners or other tools which may slip and cause injury. DON'T attempt to lift a heavy component which may be beyond your capability - get assistance. DON'T rush to finish a job, or take unverified short cuts. DON'T allow children or animals in or around an unattended vehicle. DON'T inflate a tyre to a pressure above the recommended maximum. Apart from overstressing the carcase and wheel rim, in extreme cases the tyre may blow off forcibly. DO ensure that the machine is supported securely at all times. This is especially important when the machine is blocked up to aid wheel or fork removal. DO take care when attempting to slacken a stubborn nut or bolt. It is generally better to pull on a spanner, rather than push, so that if slippage occurs you fall away from the machine rather than on to it. DO wear eye protection when using power tools such as drill, sander, bench grinder etc. DO use a barrier cream on your hands prior to undertaking dirty jobs — it will protect your skin from infection as well as making the dirt easier to remove afterwards; but make sure your hands aren't left slippery. Note that long-term contact with used engine oil can be a health hazard. DO keep loose clothing (cuffs, tie etc) and long hair well out of the way of moving mechanical parts. DO remove rings, wristwatch etc, before working on the vehicle - especially the electrical system. DO keep your work area tidy - it is only too easy to fall over articles left lying around. DO exercise caution when compressing springs for removal or installation. Ensure that the tension is applied and released in a controlled manner, using suitable tools which preclude the possibility of the spring escaping violently. DO ensure that any lifting tackle used has a safe working load rating adequate for the job. DO get someone to check periodically that all is well, when working alone on the vehicle. DO carry out work in a logical sequence and check that everything is correctly assembled and tightened afterwards. DO remember that your vehicle's safety affects that of yourself and others. If in doubt on any point, get specialist advice. IF, in spite of following these precautions, you are unfortunate enough to injure yourself, seek medical attention as soon as possible. Asbestos Certain friction, insulating, sealing, and other products - such as brake linings, clutch linings, gaskets, etc - contain asbestos. Extreme care must be taken to avoid inhalation of dust from such products since it is hazardous to health. If in doubt, assume that they do contain asbestos. Fire Remember at all times that petrol (gasoline) is highly flammable. Never smoke, or have any kind of naked flame around, when working on the vehicle. But the risk does not end there - a spark caused by an electrical short-circuit, by two metal surfaces contacting each other, by careless use of tools, or even by static electricity built up in your body under certain conditions, can ignite petrol vapour, which in a confined space is highly explosive. Always disconnect the battery earth (ground) terminal before working on any part of the fuel or electrical system, and never risk spilling fuel on to a hot engine or exhaust. It is recommended that a fire extinguisher of a type suitable for fuel and electrical fires is kept handy in the garage or workplace at all times. Never try to extinguish a fuel or electrical fire with water. Note: Any reference to a 'torch' appearing in this manual should always be taken to mean a hand-held battery-operated electric lamp or flashlight. It does not mean a welding/gas torch or blowlamp. Fumes Certain fumes are highly toxic and can quickly cause unconsciousness and even death if inhaled to any extent. Petrol (gasoline) vapour comes into this category, as do the vapours from certain solvents such as trichloroethylene. Any draining or pouring of such volatile fluids should be done in a well ventilated area. When using cleaning fluids and solvents, read the instruc- tions carefully. Never use materials from unmarked containers - they may give off poisonous vapours. Never run the engine of a motor vehicle in an enclosed space such as a garage. Exhaust fumes contain carbon mon- oxide which is extremely poisonous; if you need to run the engine, always do so in the open air or at least have the rear of the vehicle outside the workplace. The battery Never cause a spark, or allow a naked light, near the vehicle's battery. It will normally be giving off a certain amount of hydrogen gas, which is highly explosive. Always disconnect the battery earth (ground) terminal before working on the fuel or electrical systems. If possible, loosen the filler plugs or cover when charging the battery from an external source. Do not charge at an excessive rate or the battery may burst. Take care when topping up and when carrying the battery. The acid electrolyte, even when diluted, is very corrosive and should not be allowed to contact the eyes or skin. If you ever need to prepare electrolyte yourself, always add the acid slowly to the water, and never the other way round. Protect against splashes by wearing rubber gloves and goggles. Mains electricity and electrical equipment When using an electric power tool, inspection light etc, always ensure that the appliance is correctly connected to its plug and that, where necessary, it is properly earthed (grounded). Do not use such appliances in damp conditions and, again, beware of creating a spark or applying excessive heat in the vicinity of fuel or fuel vapour. Also ensure that the appliances meet the relevant national safety standards. Ignition HT voltage A severe electric shock can result from touching certain parts of the ignition system, such as Ihe HT leads, when the engine is running or being cranked, particularly if components are damp or the insulation is defective. Where an electronic ignition system is fitted, the HT voltage is much higher and could prove fatal.

Routine maintenance Refer to Chapter 7 for information relating to the 1985 on Brazilian models Introduction Periodic routine maintenance is a continuous process that commences immediately the machine is used. It must be carried out at specified mileage recordings, or on a calendar basis if the machine is not used frequently, whichever is the sooner. Maintenance should be regarded as an insurance policy, to help keep the machine in the peak of condition and to ensure long, trouble-free service. It has the additional benefit of giving early warning of any faults that may develop and will act as a regular safety check, to the obvious advantage of both rider and machine alike. The various maintenance tasks are described under their respective mileage and calendar headings. Accompanying diagrams are provided, where necessary. It should be remem- bered that the interval between the various maintenance tasks serves only as a guide. As the machine gets older or is used under particularly adverse conditions, it would be advisable to reduce the period between each check. For ease of reference each service operation is described in detail under the relevant heading. However, if further general information is required, it can be found within the manual under the pertinent section heading in the relevant Chapter. In order that the routine maintenance tasks are carried out with as much ease as possible, it is essential that a good selection of general workshop tools is available. Included in the kit must be a range of metric ring or com- bination spanners, a selection of crosshead screwdrivers and at least one pair of circlip pliers. Additionally, owing to the extreme tightness of most casing screws on Japanese machines, an impact screwdriver, together with a choice of large and small crosshead screw bits, is absolutely indispensable. This is particularly so if the engine has not been dismantled since leaving the factory. prevent the risk of unexpected failure of any component while riding the machine and, with experience, can be reduced to a simple checklist which will only take a few moments to complete. For those owners who are not inclined to check all items with such frequency, it is suggested that the best course is to carry out the checks in the form of a service which can be undertaken each week or before any long journey. It is essential that all items are checked and serviced with reasonable frequency. / Check the engine oil level With the machine standing upright on its centre stand on level ground, start the engine and allow it to idle for a few seconds so that the oil can circulate, then stop the engine. Wait one or two minutes for the level to settle and unscrew the dipstick/filler plug from the rear of the crankcase right-hand cover. Wipe it clean and insert it into the filler orifice; do not screw it in, but allow it to rest. Withdraw the dipstick; the oil level should be between the maximum and minimum level lines, ie in the cross-hatched area. If topping up is necessary use only good quality SAE10W/40 engine oil of the specified type. Do not allow the level to rise above the top of the cross-hatched area on the dipstick, and never use the machine if the level is found to be in the plain area below the cross-hatching; top up immediately. Tighten the dipstick securely and wash off any spilt oil. 2 Check the fuel level Checking the petrol level may seem obvious, but it is all too easy to forget. Ensure that you have enough petrol to complete your journey, or at least to get you to the nearest petrol station. Daily (pre-ride check) It is recommended that the following items are checked whenever the machine is about to be used. This is important to 3 Check the brakes Check the front and rear brakes work effectively and without binding. Ensure that the cable or rod linkage is lubricated and properly adjusted. Rest dipstick in position to obtain correct reading Dipstick shows allowable oil level range

Routine maintenance 4 Check the tyre pressures and tread wear Check the tyre pressures with a gauge that is known to be accurate. It is worthwhile purchasing a pocket gauge for this purpose because the gauges on garage forecourt airlines are notoriously inaccurate. The pressures, which should be checked with the tyres cold, are specified at the end of Routine maintenance and in Chapter 5. At the same time as the tyre pressures are checked, examine the tyres themselves. Check them for damage, especially splitting of the sidewalls. Remove any small stones or other road debris caught between the treads. When checking the tyres for damage, they should be examined for tread depth in view of both the legal and safety aspects. It is vital to keep the tread depth within the UK legal limits of 1 mm of depth over three-quarters of the tread breadth around the entire circumfer- ence with no bald patches. Many riders, however, consider nearer 2 mm to be the limit for secure roadholding, traction, and braking, especially in adverse weather conditions, and it should be noted that Honda recommend minimum tread depths of 1.5 mm (0.06 in) for the front tyre and 2.0 mm (0.08 in) for the rear; these measurements to be taken at the centre of the tread. Renew any tyre that is found to be damaged or excessively worn. 5 Safety check Check that the front and rear suspension is operating correctly, that the chain is lubricated and adjusted correctly and that the battery is in good condition. Check the throttle and clutch cables and levers, the gear lever and the footrests and stand to ensure that they are adjusted correctly, functioning correctly, and that all nuts and bolts are securely fastened. 6 Legal check Check that all lights, turn signals, horn and speedometer are working correctly to make sure that the machine complies with all legal requirements in this respect. Check also that the headlamp is correctly aimed to comply with local legislation. Monthly or every 600 miles (1000 km) / Check the battery The battery should be checked regularly to ensure that the electrolyte level is maintained between the level lines on the casing, that the terminals are clean and securely fastened and that the vent tube is correctly routed and free from blockages. Refer to Chapter 6.5 for details. 2 Check the final drive chain Despite its full enclosure, the final drive chain requires regular attention to ensure maximum chain life. Remove the rubber plug from the chaincase inspection aperture to check the tension and carry out temporary lubrication. The best lubricant is commercial chain lubricant, contained in an aerosol can; engine oil or gear oil are better than nothing but are flung off too quickly to be of any real use. Best of all are the special chain greases described in Chapter 5.14. Adjust the chain after lubrication, so that there is approx- imately 20 mm (|- in) slack in the middle of the lower run. Always check with the chain at the tightest point as a chain rarely wears evenly during service. Adjustment is accomplished after placing the machine on the centre stand and slackening the spindle nut, so that the wheel can be drawn backwards by means of the drawbolt adjusters in the swinging arm fork ends. The torque arm nut and the rear brake adjuster must also be slackened during this operation. Adjust the drawbolts an equal amount to preserve wheel alignment. The fork ends are clearly marked with a series of parallel lines above the adjusters, to provide a simple visual check. 3 Additional engine oil change Since the engine relies so heavily on the quantity and quality of its oil, and since the oil in any motorcycle engine is worked far harder than in other vehicles, it is recommended that the engine oil is changed at more frequent intervals than those specified by the manufacturer. This is particularly important if the machine is used at very high speeds for long periods of time, and even more important if the machine is used only at very slow speed or for very short journeys. The oil should be changed at approximate intervals of every month or every 1000 miles, depending on usage. Honda specify that the oil should be changed at least once annually or every 1 800 miles (3000 km), whichever comes first. Three-monthly, or every 1800 miles (3000 km) 1 Change the engine oil and clean the filter gauze This is the specified interval at which the engine/gearbox oil should be changed; in normal use it should be regarded as the maximum permissible. It is recommended that the oil be changed after a run to ensure that the engine is warm. This helps the oil to drain thoroughly. Obtain a container of at least 1 litre (1.76 pints) Free play can be felt via the inspection hole Move each adjuster by an equal amount

' 10 Routine maintenance capacity and place it beneath the engine unit to catch the old oil. Unscrew the drain plug on the underside of the crankcase and allow the oil to drain. Remove the large hexagon-headed plug which is located just below the left-hand engine casing. Remove the plug, followed by the spring and gauze element, and then wash all these components carefully in a suitable solvent. Wipe out any residual oil from the housing with a clean lint-free rag prior to reassembly. Refit the drain plug, tightening it to a torque setting of 2.0 - 3.5 kgf m (14.5 - 25 Ibf ft), and refill the engine with the correct quantity and grade of oil. Six-monthly, or every 3600 miles (6000 km) Repeat all service operations listed under previous headings, then carry out the following: / Clean the air filter Pull off the right-hand side panel and remove the two nuts which secure the air filter cover. Withdraw the cover, checking that the sealing gasket is in good condition, pull out the retaining spring and withdraw the element assembly. Peel off the inner and outer foam sleeves. Wash all components in white spirit (Stoddard solvent) or in warm water and detergent and dry them thoroughly. Soak the foam sleeves in the specified oil, then squeeze them gently (do not wring them out or they will be damaged) to expel all surplus oil. Refit the sleeves to the element frame. On reassembly ensure that all components are correctly fitted so that unfiltered air cannot bypass the element. 2 Check the spark plug Remove the spark plug cap, unscrew the plug and check its condition, comparing it with the photographs on page 65. If it is badly worn or fouled it must be renewed. If it is fit for further service check the gap and reset it if necessary, as described in Chapter 3.8. 3 Check the valve clearances It is important that the correct valve clearance is maintained. A small amount of free play is designed into the valve train to allow for expansion of the various components. If the setting deviates greatly from that specified, a marked drop in performance will be evident. In the case of the clearance becoming too great, it will be found that valve operation will be noisy, and performance will drop off as a result of the valves not opening fully. If on the other hand, the clearance is too small the valves may not close completely. This will not only cause loss of compression, but will also cause the valves to burn out very quickly. In extreme cases, a valve head may strike the piston crown, causing extensive damage to the engine. The clearances should be checked and adjusted with a cold engine. Place the machine on its centre stand and remove the rocker cover, taking care not to damage the 0 ring. Remove the gearchange pedal and the left-hand outer cover to expose the generator rotor. Remove plug and allow old oil to drain Remove the spark plug, then slowly rotate the engine anti- clockwise by way of the generator rotor, watching the inlet valve. When it has opened and closed again (sunk down and risen up to its original position), rotate the engine further until the T mark on the rotor periphery aligns exactly with the raised index mark which is positioned between 12 and 1 o'clock (from the crankshaft) on the generator stator. The engine will then be in the correct position for checking the valve clearances, namely at Top Dead Centre (TDC) on the compression stroke; check that there is free play at both rockers. Using a 0.08 mm (0.003 in) feeler gauge, check the clearance between the top of each valve stem and its cor- responding rocker. The feeler gauge must be a light sliding fit, with the rocker and valve stem just nipping it. If necessary, slacken the locknut, and turn the small square-headed adjuster to obtain the correct setting. Tighten the locknut, holding the adjuster at the same time to prevent it from moving. Finally, recheck the setting and then repeat the procedure on the other rocker. 4 Check the contact breaker points and ignition timing Note: since the generator stator plate is located by its countersunk retaining screws, the ignition timing can only be altered by opening or closing the contact breaker gap; therefore both operations are described as one. The full procedure is given here for ease of reference, but if the points are found to be in good condition and if the gap has not altered or is within the tolerance, then the ignition timing will be sufficiently accurate and there will be no need to carry out the full check. First remove the gearchange pedal, the left-hand outer cover, the spark plug and the left-hand side panel. Strainer is easily removed for cleaning Dismantle the element for cleaning -j- mark should align as shown and lubrication

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1976-1992 Honda CG125 Service & Repair Manual

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