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Professional Shop Manual
AC3 Series of 4-Cycle Engines
NOTE: These materials are for use by trained technicians who are experienced in the service and repair of outdoor power
equipment of the kind described in this publication, and are not intended for use by untrained or inexperienced individuals.
These materials are intended to provide supplemental information to assist the trained technician. Untrained or inexperi-
enced individuals should seek the assistance of an experienced and trained p
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Table of Contents Chapter 1: Introduction ............................................................................................1 Professional shop manual intent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Fasteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Description .
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Chapter 6: Starters .................................................................................................43 Recoil Starter Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 The starter rope, pulley and springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Electric starter system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Chapter 7: Clutch and Upper Drive Shaft .....
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Introduction CHAPTER 1: INTRODUCTION Professional Shop Manual intent This Manual is intended to provide service dealers with an introduction to the mechanical aspects of the AC3 series of 4-cycle engines. Disclaimer: The information contained in this manual is correct at the time of writing. Both the product and the infor- mation about the product are subject to change without notice. About the text format: NOTE: is used to point out information that is relevant to the procedure, but does not f
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AC3 Series of engines Assembly Torque specifications may be noted in the text that covers assembly, they may also be summarized in tables along with special instructions regarding locking or lubrication. Whichever method is more appropriate will be used. In many cases, both will be used so that the manual is handy as a quick-reference guide as well as a step-by-step procedure guide that does not require the user to hunt for information. The level of assembly instructions provided will be dete
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Introduction AC3 • 29cc’s of displacement. Engine cover splits front to • Engine covers split front and back. back •Metal sump Figure 1.3 AC4 • 32 cc’s of displacement. • Aluminum clutch housing. Aluminum clutch housing • Extended oil fill tube that is near the carburetor. • End mounted recoil starter. oil fill tube Figure 1.4 AC5 • 25 cc’s of displacement. Plastic clutch • Identical to the AC4 except for the plastic clutch housing housing. Figure 1.5 3
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AC3 Series of engines Model and Serial Numbers The model (item) and serial number are on a little white sticker with bar code. These are the numbers needed when ordering parts. This sticker can be found on the side of the engine. Serial number Model number Figure 1.6 The model number is 41ADT59C711. The break down of what the number mean is as follows: 41 ............................................................................................ Hand held product ........A.............
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Maintenance CHAPTER 2: MAINTENANCE MAINTENANCE The information in this manual applies to the AC3 series of engines. Some basic principles may apply to engines produced by other manufacturers. As the saying goes “an ounce of prevention is worth a pound of cure”. The same can be said about preventive maintenance on outdoor power equipment. By changing the spark plug, air filter, and oil at recommended intervals many failures can be avoided. Sometimes just clearing off yard debris that has colle
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AC3 Series of engines Spark plugs The spark plug used in the 32cc trimmer is a Cham- pion RDZ19H gapped to 0.025” (.655 mm). See Figure 2.3. Wear rate will vary with severity of use. If the edges of the center electrode are rounded-off, or any other appar- ent wear / damage occurs, replace the spark plug before operating failure (no start) occurs. Cleaning the spark plug: NOTE: We do not recommend cleaning spark plugs. • Use of a wire brush may leave metal deposits on t
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Maintenance Air filter A dirty air filter can reduce engine power, increase fuel consumption, increase CO emissions and make starting more difficult. The air filter should be cleaned every 10 hours of use (depending on area of use, dusty areas require more frequent cleanings). To clean/replace the air filter: Air filter cover 1. Remove the air filter cover by pressing in the tab on the bottom of the filter housing and lifting the cover off. See Figure 2.5. Press tab Figure 2.5 2. Pull t
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AC3 Series of engines Spark arrestor Engine cover The spark arrestor should be checked and/or cleaned every 25 hours of use. NOTE: The spark arrestor also serves to keep blockages out of the exhaust system. Typical block- ages include insect nests built during the dormant Screws season. NOTE: A spark arrestor is required by law when trimmer are used near “unimproved” land. To check/clean the spark arrestor: 1. To clean the spark arrestor remove the engine cover using a T-20 driver. See Figu
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Maintenance Fuel filer A dirty fuel filter can result in a lean run condition. The fuel filter should be replaced every 25 hours of use. NOTE: The weighted fuel filter (clunk) keeps the filter sub- merged in the fuel at any angle of operation. The filter removes dirt and air bubbles from the fuel. Running the trimmer without the filter may allow air into the fuel line creating a lean run condition at higher RPMs. This will cause a catastrophic failure of the engine. To replace the fue
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AC3 Series of engines Valve lash To adjust the valves: NOTE: Loose valve lash on these engines can mimic the symptoms of a lean fuel/air mix- ture. Valve cover 1. Remove the engine cover and spark plug, following the steps described in the previous sections of this chapter. 2. Remove the valve cover using a T-25 driver. See Figure 2.13. 3. Rotate the crankshaft to bring the piston to top dead center of the compression stroke (valves closed). NOTE: Use a probe in the spark plug hole t
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Troubleshooting CHAPTER 3: TROUBLESHOOTING Definitions Troubleshooting - The act of gathering information by preforming tests and direct observations. Diagnosis - A theory of what the problem is, based on the information gathered by troubleshooting. Introduction Diagnosing an engine is an art form that is built on several factors. First and most importantly is a good under- standing of how the engine works. The second is a skill set that has been honed by experience. Finally the use of visual o
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AC3 Series of Engines There are tools that the technician can use in order to define the problem, such as: 1. Interview the customer. • Get a good description of their complaint. • If it is an intermittent problem, verify what conditions aggravates the problem as best as possible. • Get an accurate service history of the equipment. • Find out how the customer uses and stores the equipment. 2. Direct observation: • Do not take it that the customer is correct with their description of the problem.
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Troubleshooting Identify factors that could cause the problem This is the second step in the troubleshooting process. 1. Crankshaft will not turn. • Hard to pull rope, steady pressure - This usually indicates a mechanical bind of some sort. the likely sus- pects are: II. A parasitic load from a jammed attachment or drive shaft. III. An internal drag from a scored or seized piston. • Rope jerks back - This usually indicates that the piston is stopping before top dead center on the com- pression s
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AC3 Series of Engines • Compression or ignition problem I. Check the engine stop and/or ignition switch. II. Test the ignition system using a proper tester. III. Replace the spark plug with a new one or a known good one. IV. Check compression. V. Check valve lash. VI. Check valve timing/actuation. VII. Check exhaust. 8. Starts, runs poorly • Starts, then dies I. Run the engine with a spark tester in-line between the spark plug wire and the spark plug or use an oscilloscope and see if the spark
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Troubleshooting II. The muffler itself my be blocked. III. The spark arrestor may be blocked. IV. The exhaust valve may not be opening fully, possibly because of extremely loose valve lash set- tings. V. The exhaust valve seat may have come loose in the cylinder head. This may cause a loss of com- pression, a flow blockage or it may randomly alternate between the two. NOTE: The cause of an exhaust valve seat coming loose is usually over-heating. VI. Intake blockage a. An intake blockage up-strea
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AC3 Series of Engines •Knock * Check for loose mounting of engine or driven implement * Rotate crankshaft back-and-forth to check for loose connecting rod. • Click * Half-engine speed clatter: loose valve lash. * Half-engine speed clatter, slightly heavier: wrist-pin. * Rhythmic heavy-light engine speed click: piston slap • Spark-knock * Advanced ignition timing * Low octane fuel * Over-heating engine (check for blocked cooling air flow) * Carbon build-up in cylinder: glowing carbon chunks pre-
