For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Professional Shop Manual 61/65/70 Series Horizontal Shaft 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.
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For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Table of Contents Chapter 1: Introduction ......................................................................................................... 1 Professional Shop Manual intent ........................................................................................ 1 Assembly ............................................................................................................................ 1 Maintenance .......................
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 4: The Fuel System and Governor .......................................................................26 Inspecting the fuel............................................................................................................. 26 Test fuel for alcohol .......................................................................................................... 26 Fuel tank vent ...................................................
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 7: Ignition System .................................................................................................. 50 Troubleshooting the ignition system................................................................................. 50 Stop switch ........................................................................................................................51 Remote (ignition) stop switch ..............................
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For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION CHAPTER 1: INTRODUCTION Professional Shop Manual intent Fasteners This manual is intended to provide service dealers with an introduction proven diagnostic and repair procedures for the MTD horizontal shaft engines. • Most of the fasteners used on the MTD engine are metric. Some are fractional inches. For this reason, wrench sizes are frequently identified in the text, and measurements are given in U.S. and metric scales.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 1: INTRODUCTION M T D H o riz o n ta l E n g in e M o d e l D e s ig n a to rs S ta rte r/A lte rn a to rs 1 6 1 - S H A 1 = R e c o il s ta rt 2 = E le c tric s ta rt 3 = E . s ta rt/a lt. 2 0 W /2 0 W 4 = E . s ta rt/a lt. 3 A D C /5 A M a jo r R e v is io n Change C o m p lia n c e U H C 0 (Z e ro ) G W B o re D ia . (m m ) U n ite d S ta te s (5 0 S ta te ) E u ro p e C a lifo rn ia 4 9 S ta te U .S .
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION MAINTENANCE 2. Wear rate will vary somewhat with severity of use. If the edges of the center electrode are rounded-off, or any other apparent wear / damage occurs, replace the spark plug before operating failure (no start) occurs. 3. Cleaning the spark plug: The information in this manual applies to the MTD engine. Some basic principles may apply to engines producted by other manufacturers.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 1: INTRODUCTION Air filters Generally air filters come in two different types, a pleated-paper element, or a foam plastic, sometimes a combination of the two will be used like the one on the MTD engine. See Figure 1.2. Pre-filter and filter together 3. The filter should be checked on a regular basis; possibly several times in a season. 4. Typically an air filter should be changed before every season. 5.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION • Oil type and capacity 1. To check the oil, twist and remove the dip-stick from the engine. Clean the oil off of the tip of the dipstick. Re-insert the dipstick without threading it in to get the oil level reading. See Figure 1.3. No oil additives or viscosity modifiers are recommended. The performance of a good oil meeting the API specifications will not be improved by oil additives.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 1: INTRODUCTION To replace the fuel filter: Fuel Gasolines currently on the market are not pure gas. Today’s fuels have alcohol and other additives in them to reduce emissions. The fuel make up can vary seasonally and geographically. NOTE: On snow blower engines, the engine shroud must be removed to reach the fuel line. Refer to Chapter 3: Air intake systems for directions on how to remove it.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION Valve lash 5. Valve lash is the clearance between the top of the valve stem and the rocker arm. The valve lash should be checked after the first 25 hours of use and every 100 hours after that. Valve lash can be checked and adjusted using the following steps: 1. NOTE: If care is taken not to damage the valve cover gasket, it can be re-used. If the engine has been run, allow it to cool thoroughly.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 1: INTRODUCTION 9. Intake valve lash (carburetor side) should be .003”-.005” (.10 + .02mm). See Figure 1.10. .004” feeler gauge 13. Double-check the clearance after tightening the jam nut, to confirm that it did not shift. Re-adjust if necessary. 14. Rotate the engine through several compression cycles: • Observe the movement of the valve gear.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION General torque specifications Grade 4.8 5.8 8.8 10.9 12.9 Noncritical Fasteners in Aluminum size in-lbs Nm in-lbs Nm in-lbs Nm in-lbs Nm in-lbs Nm in-lbs Nm M4 M5 M6 M8 11 22 38 93 1.2 2.5 4.3 10.5 15 28 50 120 1.7 3.2 5.7 13.6 26 51 88 216 2.9 5.8 9.9 24.4 36 72 124 300 4.1 8.1 14 33.9 44 86 146 360 5 9.7 16.5 40.7 18 35 60 150 2 4 6.8 17 size M10 M12 M14 ft-lbs 16 27 43 Nm 21.7 36.6 58 ft-lbs 20 35 55 Nm 27.1 47.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING CHAPTER 2: BASIC TROUBLESHOOTING Definitions Define the problem Troubleshooting - The act gathering information by preforming tests and direct observations. The first step in troubleshooting is to define the problem: 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 upon several factors.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING I. Cleanliness of the equipment will indicate the level of care the equipment has received. Identify factors that could cause the problem This is the second step in the troubleshooting process. 1. II. Make sure the engine and attachments are securely fastened. Crankshaft will not turn. a. III. The tune-up factors. NOTE: Most hard starting and poor running conditions can be solved by preforming a tune-up.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING IV. Bent crankshaft (unrepairable) 3. V. Internal binding, crankshaft, connecting rod or piston (unrepairable) 2. Starts, runs poorly 3a. Starts, then dies I. Crankshaft turns, no start. 2a. Most gasoline engine diagnosis involves isolating problems in the four critical factors an engine needs to run properly: I. II. Check choke operation.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING V. Low compression float valve stuck or metering / emulsion issues with the carburetor. a. Check valve lash b. Check compression b. White smoke, usually heavy c. • Oil in muffler, usually the result of improper tipping. the engine will “fog” for a minute or so, then clearup on its own. • Massive oil dilution with gasoline. It may be caused by improper tipping.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING engine run artificially lean. ing into play as the engine RPMs cross the activation threshold. This will have no ill effects on engine performance. c. Skip • Usually ignition related. • Half-engine speed clatter: loose valve lash. • • Half-engine speed clatter, slightly heavier: wrist-pin.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Repairing the problem Prime test The third step in the troubleshooting process is to repair the problem. This step consists of: To perform a prime test: 1. Form a diagnosis by using all of the information gathered from the troubleshooting that was performed. 2. Physically preform the repair. 1. NOTE: Inspect the air filter while priming the engine.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Leak-down test 3. Connect tester to compressed air. A leak-down test is the preferred method to test the engine’s ability to compress the charge. It will also show where pressure is leaking from. 4. Adjust the regulator knob until the needle on the gauge is in the yellow or set area of the gauge. 5. Connect the tester to the adapter.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Compression test 3. Interpreting compression readings. To perform a compression test: Table 2: NOTE: Compression should be in the range of 40-60 PSI (2.81-4.1 Bar). Readings in psi • Disconnect the high-tension lead from the spark plug and ground it well away from the spark plug hole. <20 (1.38 Bar) • Remove the spark plug using a 13/16” or 21mm wrench. A flexible coupling or “wobbly” extension may help.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING PCV testing 2. The PCV valve is located in the valve cover and allows the crankcase pressure to escape. Leakage and blockage are the two failure modes for a PCV system. Either mode will cause crankcase pressure to build-up, though the effects of a blocked PCV are generally more dramatic. Increased case pressure will result in oil entering the combustion chamber. 1.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS CHAPTER 3: AIR INTAKE SYSTEMS MTD builds horizontal crank engines for snow blowers and chore performers. The differences between snow engines and chore engines are the muffler and the air intake system. Therefore the air intake system for the snow and chore engines will be discussed separately, as will the mufflers in a later chapter. 4. Pull off the choke and throttle knobs. See Figure 3.2.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS 7. Remove the screw that fastens the engine shroud by the fuel tank using a #2 phillips screw driver. See Figure 3.4. 9. Work the engine shroud off of the carburetor studs. NOTE: Be careful to pop the primer line out of the notch that secures it while working the engine shroud off. See Figure 3.6. Remove this screw Pop primer line out of notch while working the shroud off Figure 3.4 8.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS 12. 13. Slide the carburetor off of the carburetor studs. Chore engines NOTE: The choke linkage will come off with the carburetor. Air filters Generally air filters come in two different types, a pleated-paper element or foam. A combination of the two are used on the MTD engine. See Figure 3.9. Unhook the spark plug wire from the clip in the carburetor insulator. Slide the insulator off of the carburetor studs.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS To service the air filter: Air filter base and intake elbow 1. To remove the air filter base: Press in on the tab in the air filter cover. See Figure 3.10. 1. Remove the air filter following the steps described in the previous section. 2. Remove the two screws that hold the air filter base to the intake elbow. See Figure 3.12. Press here Mounting screws Figure 3.10 Intake elbow 2.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS 6. Inspect the air intake gasket. Carburetor Insulator NOTE: The air intake gasket is a Vulcanized metal gasket. If the rubber is not ripped or deformed, it can be reused. See Figure 3.14. CAUTION: When working around the fuel system, do not bring any sources of heat, spark, or open flame near the work area. 1. Remove the intake elbow by following the previously described steps.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS 2b. Disconnect the throttle linkage and return spring. See Figure 3.16. 3. Unhook the spark plug wire from the clip molded into the insulator plate. See Figure 3.18. Spark plug wire Throttle linkage Clip Return spring Figure 3.16 Figure 3.18 NOTE: The carburetors are not inter-changeable from one engine model to another.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS NOTE: An insulator block separates the carburetor from the cylinder head. There is a gasket on each side of the insulator. See Figure 3.19. Insulator plate Gaskets Figure 3.19 NOTE: The gaskets are different, and there is an orientation to the insulator. • The gasket with the “D” shaped opening goes between the insulator and the cylinder head, matching the shape of the gasket to the shape of the intake port.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR CHAPTER 4: THE FUEL SYSTEM AND GOVERNOR The function of the fuel system is to store, mix the fuel with air and deliver it to the combustion chamber. The fuel system consists of the following components: • Fuel tank • Fuel lines • Fuel filter • Carburetor Test fuel for alcohol: Fuels currently on the market contain a wide array of additives. Some of these additives oxygenate the fuel.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR To test the cap vent Generally these kits involve mixing a measured amount of water and gas together and seeing were the boundary layer is. See Figure 4.2. 1. Clean off the vent. 2. Blow air into the vent hole. The air should blow throw the vent with little back pressure. 3. Suck air through the vent hole. Air should freely enter through the vent.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Inspect the fuel lines The fuel tank • Are they cracked? To remove the fuel tank: • Are they clogged? 1. Drain the tank. • Are they brittle? 2. Disconnect the fuel line from the tank by following the steps described in the fuel filter section of Chapter 1: Introduction. 3. Remove the dip stick 4. Remove the dip stick tube cover by removing the two screws. See Figure 4.5.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Choke NOTE: On snow engines with electric start, the starter switch mounting bracket is bolted to the fuel tank and will come off with the tank. If replacing the tank, make sure to remove the bracket from the old tank and mount it on the new one. See Figure 4.7. MTD engines are equipped with a choke, a primer or both. If equipped with a manual choke, it must be closed to start the engine.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Choke linkage Primers The rod connecting the choke knob to the choke plate on the carburetor can be bent slightly to facilitate adjustment. To access it: MTD engines use a dry bulb primer. This means that there is no fuel in the primer bulb. The primer works by pushing air into the float chamber of the carburetor when the primer bulb is depressed.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR To replace the primer: Carburetors 4. If the primer is bad, disconnect hose from the carburetor. 5. Remove the hose camp at the rear of the primer bulb. See Figure 4.13. If diagnosis indicates a fuel problem, inspect the carburetor. This is important even if problems are identified elsewhere in the fuel system..
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Disassembly and rebuilding the carburetor 1. 3. Clamp-off the fuel line to prevent fuel spillage, then disconnect the fuel line from the carburetor. Float bowl NOTE: If the carburetor is equipped with a primer, disconnect the primer hose. 2. Drain bolt Remove the carburetor by following the steps described in Chapter 3: Air Intake and Filter.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR 5. Remove the pin that the float hinges on to remove the float. 6. NOTE: The float is not adjustable. Spring tension against the float valve begins to build from the horizontal position, putting progressively more pressure between the tip of the valve and the seat. See Figure 4.17. Remove the main jet using a narrow-shank straight blade screwdriver. See Figure 4.18.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR 8. NOTE: The main jet secures the emulsion tube in the central column of the carburetor. See Figure 4.19. Carefully pry out the metering plug using a small screwdriver. See Figure 4.21. Emulsion air port: pilot jet Emulsion tube Main jet Bowl vent ports Figure 4.21 Emulsion air port: main jet 9. Figure 4.19 7. Examine the metering plug: See Figure 4.22.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR 14. NOTE: The pilot screw regulates how much of this pre-mixed fuel/air emulsion is allowed to enter the throat of the carburetor, to atomize down-stream of the throttle plate. On current production units it is set at the factory and the screw head is removed. See Figure 4.23. Transition ports Start engine and check the idle RPM using a tachometer.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Governor Governor arm The engine speed is controlled by a balance between the force applied by a spring (pulling the throttle open) and a flyweight mechanism within the engine applying force to the governor arm (pushing the throttle closed). See Figure 4.25. To remove the governor arm from the governor shaft: 1. Remove the fuel tank by following the steps described in the Fuel Tank section of this chapter.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Governor shaft 7. Check the movement of the fly-weights and cap on the governor gear. 8. Install the shaft by following the above steps in reverse order. 9. Install the engine on the equipment it powers. 10. Test run the engine and adjust the top no load engine rpms by following the steps described in the carburetor section of this chapter. To remove or replace the governor shaft: 1.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Governor cup and the governor gear 6. To remove or replace the governor gear and cup: 1. Remove the engine from the unit. 2. Remove the governor arm by following the previously described steps. 3. Remove the flywheel by following the steps described in Chapter 7: Ignition Systems. 4. Remove the sump and crankshaft by following the steps described in Chapter 10: Cam, Crankshaft and Piston. 5.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 LUBRICATION CHAPTER 5: LUBRICATION Oil type and quantity Oil dip stick Use a quality motor oil certified to meet or exceed American Petroleum Institute (A.P.I.) requirements for service classification SG/SF. Motor oils classified SG/ SF will show this designation on the container. To check the oil level: NOTE: Be sure to check the engine on a level surface with the engine stopped.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 LUBRICATION Dip stick tube removal 4. To remove/replace the dip stick tube: 1. Remove the dip stick. 2. Remove the two screws securing the dip stick cover in place using a #2 phillips screw driver. See Figure 5.4. Pull the dip stick tube out of the engine block and fuel tank. See Figure 5.6. Remove these screws Figure 5.6 Figure 5.4 3. 5. Inspect the O-rings on the dip stick and the dip stick tube. Replace if damaged. 6.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 LUBRICATION Lubrication system The second oil passage runs along the bottom side of the cylinder. This is the oil return passage. As the name implies, it allows the oil collecting in the cylinder head to return to the sump. The return passage is the tiny hole that is in between the two tappet passages. MTD uses a splash lube system for it’s horizontal shaft engines.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 LUBRICATION Positive crankcase ventilation valve The PCV valve is located inside the valve cover. The function and test procedures for the PCV valve is covered in Chapter 2: Basic Troubleshooting. NOTE: The PCV valve is not serviceable. If it is faulty, the valve cover must be replaced. 4. To remove the valve cover and PCV valve: 1. Disconnect and ground the spark plug wire. 2.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS CHAPTER 6: STARTER AND CHARGING SYSTEMS Recoil Starter Removal Starter Cup To remove recoil assembly from the engine: The starter cup is a steel cup that is bolted to the flywheel. 1. Remove the three nuts that secure the recoil assembly to the engine using a 8mm wrench. See Figure 6.1. 1. Inspect the inside of the starter cup. See Figure 6.2. Starter cup Inspect slots Remove these screws Figure 6.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS 3. Install a starter cup by placing it on the flywheel, with the dimple on the bottom of the starter cup in the dimple in the flywheel. See Figure 6.3. Starter Rope The most common failure mode for most recoil assemblies is a broken rope. NOTE: If the spring was not damaged when the recoil sprung back, It is possible to simply remove the remnants of the old rope and install a new rope.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS 7. Install the handle and handle insert on the loose end of the rope, again using a double half-hitch. See Figure 6.5. Starter pulley and recoil spring The recoil spring is nested within the starter pulley and both parts are sold as a single part number. CAUTION: Eye protection should be worn if the starter pulley is to be removed. Inset: knot If damage is suspected, the recoil may be disassembled by: 1.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS 4. Inspect the pawls and torsion springs for wear and damage. See Figure 6.8. NOTE: Evaluate the damage, including parts prices and local labor rates. In some parts of the country, it makes economic sense to replace the complete assembly, in other areas labor rates favor repair. Torsion springs 6.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Electric starter The electric starter is only available on the snow engine. It is powered by an extension cord that is plugged into household 120 volt AC current. The starter and switch assembly are one piece and are not serviceable. NOTE: Before condemning a starter make sure to bench test it. To bench test a starter: A. Remove the starter from the engine. B. Plug the extension cord into the switch housing.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Charging system Testing Description The charging system will produce AC and DC voltages. The rectifier for the DC voltage is inside of the stator and is not serviceable. To test the charging system: Some engines are equipped with a charging system. The charging system consists of: • • Alternator stator: copper field windings around an iron core.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS 8. Move the red (+) to the red wire of the charger harness. See Figure 6.15. Stator To remove/replace the stator: Red wire 1. Remove and ground the spark plug wire. 2. Remove the flywheel by following the steps described in Chapter 7: Ignition System. 3. Remove the baffle that covers the charger harness using a 10mm wrench. 4.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM CHAPTER 7: IGNITION SYSTEM Troubleshooting the ignition system The purpose of the ignition system is to provide a spark in the combustion chamber at the proper time to ignite the fuel/air mixture. The steps in troubleshooting the ignition system are: 1. CAUTION: Never remove the spark plug and hold it against the cylinder head to test for spark. The fuel/air mix coming out of the spark plug hole will catch on fire.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Stop switch • All MTD horizontal engines that are in use in North America have a stop switch built into the throttle lever assembly. MTD engines used on snow blowers have an additional stop (ignition) switch in the engine shroud. When the throttle is all the way to the right (stop), the multimeter should read at or near 0.0Ω, indicating continuity. See Figure 7.3.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Remote (ignition) stop switch • With the key removed, the meter should show continuity. See Figure 7.7. To test the remote stop switch: Continuity 1. Remove the muffler cover. 2. Disconnect the two wires from the remote switch. See Figure 7.5. Disconnect wires Key removed Remote switch Figure 7.7 5. Figure 7.5 3. Connect a digital multimeter to the two tabs on the back of the remote switch. 4.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM 8. Set the multimeter to the ohms (Ω) scale. The module • If the multimeter shows continuity, replace the module. The coil in this ignition system is an inductive discharge magneto, contained in a single module. • If the multimeter does not show continuity, check the wire for a break and check the ground connection. See Figure 7.9. • The inductive discharge magneto has a two leg design.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM • At operating speed, the ignition should produce voltage approaching 12,000. See Figure 7.11. Module removal 1 reticle = 4,000 Volts waveform is 3 reticles tall Unplug the spark plug. 2. Remove the Heatbox (snow engines) and intake elbow by following the steps described in Chapter 3: Air Intake Systems. 3. Unhook the spark plug wire from the clip in the carburetor insulator. See Figure 7.13.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Installing the module and setting the air gap Flywheel NOTE: If just setting the air gap, loosen the module mounting screws first then follow the same steps as described below. 1. The flywheel holds the magnets that induce a field in the module which in turn produces a spark. But it also controls the timing of the ignition system by controlling when the magnets are introduced to the module.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM 5. Inspect the key, keyway, and tapered mating surfaces of the flywheel and crankshaft. See Figure 7.16. About the spark plug Taper • The spark plug is a Torch model F6RTC, gapped to .024”-.032” (.60-.80 mm). • Champion RN14YC or NGK BPR4ES are physically similar but do not match the F6RTC in heat range. This difference in heat ranges will effect performance and emissions.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Spark plug removal 1. Disconnect and ground the spark plug wire. 2. Remove the spark plug using a 13/16” or 21mm wrench. A flexible coupling or “wobbly” extension may help. See Figure 7.17. 13/16” spark plug socket Muffler Valve cover High tension lead Figure 7.17 3. Gap a new spark plug to .024”-.032” (.60-.80 mm). 4. Install the new spark plug and tighten to a torque of 15 - 18 ft - lbs (20-25 Nm). 57 www.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 EXHAUST CHAPTER 8: EXHAUST The exhaust system is a frequently overlooked component of an engine. It is important to make sure the muffler is in good condition and free of debris and/or insects. If The spark arrestor needs to be cleaned or replaced: 1. NOTE: A blocked muffler will result in poor performance. If a muffler is completely blocked the engine may not start.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 EXHAUST 4. The spark arrestor can be: • Replaced • Cleaned by mechanical means • Solvent cleaned • Burned clean using a butane or propane torch. 5. Install the spark arrestor by following steps 1-3 in reverse order. NOTE: The MTD engine uses a graphite exhaust gasket. It is not reusable and must be replaced every time the muffler nuts are loosened.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 EXHAUST Snow engines 3. Unlike the summer engines, the snow engines are not equipped with spark arrestors. Remove the two muffler nuts using a 13mm wrench and lift the muffler off of the engine. See Figure 8.8. To remove/replace the muffler: 1. Remove the muffler shroud by taking off the six screws that hold the muffler cover in place using a 10 mm wrench. See Figure 3.6. Muffler nuts Muffler shroud Figure 8.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD CHAPTER 9: CYLINDER HEAD The Cylinder head of the MTD engine can be removed without removing the engine from the piece of equipment. 6. Remove the throttle lever by removing the two screws using a 8mm wrench. See Figure 9.2. To remove the cylinder head: 1. Disconnect and ground the spark plug high tension lead. 2. Remove the spark plug using a 13/16” or 21mm wrench. 3.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD 9. Remove the four screws securing the valve cover using a 10mm wrench. See Figure 9.4. 13. Remove the cylinder head bolts using a 12mm wrench. See Figure 9.6. Cylinder head bolts 4 1 2 3 Remove valve cover Figure 9.6 Figure 9.4 10. Loosen the jam nuts and fulcrum nuts that secure the rocker arms using a 10mm wrench and a 14mm wrench. See Figure 9.5. 14. Lift the cylinder head off of the engine. 15.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD To install a cylinder head: 19. Insert the push rods. 16. 20. Install the rocker arms. 21. Adjust the valve lash by following the steps described in Chapter 1: Introduction. 22. Install the carburetor and air cleaner, using new gaskets, by following the steps described in Chapter 3: Air Intake 23. Install the muffler by following the steps described in Chapter 8: Exhaust. 24.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD Valves Valves and valve parts, like springs and keepers, are not available as service parts. The valves and valve seats can be serviced by grinding and lapping or the head can be replaced. Depending on local machine and labor costs, it is probably more economical to replace the cylinder head versus servicing the valves. NOTE: The exhaust valve has a secondary keeper on it.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD 6. Inspect the valve seat. See Figure 9.13. 8. Inspect the valve springs. NOTE: Valve spring free length should be at least 1.22” (28.5mm). Original length is 1.44” (36.6mm). 9. Install the valves in the cylinder head by following steps 2 - 5 in reverse order. 10. Test the valves for leaks by: 10a. .043-.050” Place the cylinder head on a couple of wood blocks with the valves facing up. 10b.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD Push rod bushings 7. Remove the rocker studs. See Figure 9.15. The MTD engine has bushings for the push rods that need to be replaced from time to time. An indication that the bushings are worn is that the valve lash loosens up. This is because the push rods start moving side to side which opens up the valve lash. 8. Lift the push rod bushing plate out of the cylinder head. See Figure 9.16.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD CHAPTER 10: CRANKSHAFT, PISTON AND CONNECTING ROD There are a a few different paths that can be followed when disassembling an engine. This chapter will cover the removal of components in one order, but it is written so that the technician can jump around, the exact method depends on the type of repair that needs to be made. 10. Carefully slide the crank case cover off of the crank shaft. 11.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD 13. Remove the valve tappets. See Figure 10.3. 15. Push the piston out of the cylinder. 16. Remove the piston rings from the piston using a pair of piston ring pliers. See Figure 10.5. Piston ring pliers Valve tappets Figure 10.3 NOTE: Keep track of which tappet was originally riding on which lobe. Be sure there are reassembled that way. 14. Figure 10.5 17. Remove the crank shaft. See Figure 10.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD The internal components of the MTD engine are not available as service parts. The intent of this chapter is to provide the technician the procedures to examine an engine and to provide the specification to determine if an engine is worn out. All of the specifications are listed in a chart at the end of the chapter. 4. Measure the crankpin using a vernier caliper or a micrometer. See Figure 10.8.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Piston Inspection 1. Clean the piston and remove all carbon from the rings and ring groves. 2. Clean the cylinder bore and remove all carbon. 3. Insert one ring into the cylinder. Push it down about one inch from the top. See Figure 10.9. NOTE: Typically there is a top and bottom profile to compression rings, But the compression rings on the MTD are symmetrical. See Figure 10.10.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Connecting rod inspection Cylinder inspection 1. Inspect the connecting rod for cracks or any signs of damage. 1. 2. Install the rod cap and tighten to a torque of 106 -124 in-lbs (12 - 14Nm). 3. Measure the inside diameter of the connecting rod and compare the measurements to those listed in the chart at the end of this chapter. See Figure 10.12. Clean and inspect the cylinder, inside and out.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD 2. Compare the measurements to those that are listed in the chart at the end of the chapter. 3. Inspect the cylinder cross hatch. Bearings There are two bearings to inspect; a bearing in the crank case cover and one in the cylinder block. To inspect the bearings: NOTE: The cross hatch is important because it helps hold oil on the cylinder walls. 1.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Reassembly 1. Clean the cylinder NOTE: Use an old piece of microfiche or a seal protector to protect the oil seal lip while inserting the crank shaft. See Figure 10.17. 1a. Remove all gasket material from all mating surfaces. 1b. Clean the cylinder and crank case cover. 2. Oil seals 2a. Install a new oil seal in the cylinder block. 2b. Install a new seal in the crank case cover. See Figure 10.16.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD bolts to a torque of 106 -124 in-lbs (12 14Nm). See Figure 10.21. 4c. Slide the connecting rod and piston into the cylinder. NOTE: The arrow on the piston must point towards the push rod cavity. See Figure 10.19. arrow Install the connecting rod cap Figure 10.21 push rod cavity Figure 10.19 5. Install the valve tappets. 6. Install the cam shaft by: 4d.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD 9. Using a seal protector, slide the crankcase cover on to the crank shaft. See Figure 10.23. Seal protector Figure 10.23 10. Gently rock the crank case cover until it seats fully against the cylinder block. 11. Install the crank case cover bolts and tighten to a torque of 80 - 106 in-lbs (9 - 12 Nm). NOTE: Use a star torque pattern to tighten the cover bolts. 12.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Engine specifications chart Table 1: Specification 61 65 70 Bore (new) 2.4” (61mm) 2.6” (65mm) 2.76” (70mm) Displacement 7.5 in^3 (123 cc) 10.9 in^3 (179cc) 12.7 in^3 (208 cc) Bore maximum diameter 2.386” (61.17mm) 2.566” (65.168mm) 2.763” (70.180mm) Crank journal (flywheel end) Min. diameter 0.970” (24.879mm) 0.970” (24.879mm) 0.970” (24.879mm) Crank journal (PTO end) min.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Engine torque values chart Table 2: Fastener Torque 61 65 70 Blower housing 80 - 106 in-lbs (9-12 Nm) 80 - 106 in-lbs (9-12 Nm) 80 - 106 in-lbs (9-12 Nm) Carburetor drain bolt 80-106 in-lbs (9-12 Nm) 80-106 in-lbs (9-12 Nm) 80-106 in-lbs (9-12 Nm) Carburetor mounting nuts 80-106 in-lbs (9-12 Nm) 80-106 in-lbs (9-12 Nm) 80-106 in-lbs (9-12 Nm) Connecting rod cap bolts 106 -124 in-lbs.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS CHAPTER 11: FAILURE ANALYSIS 1. A properly maintained engine will provide years of service. Occasionally an engine will fail. An important part of working on engines is finding out why they failed. Was it something the customer did? Was it a manufacturing defect? Did the engine just wear out? All of these questions need to be answered when a failed engine is found.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS 3. Particles that enter the intake system travel at great speed and act like sand blasting media inside the engine. This causes wear to the parts affected. Other sources of abrasives that get into the engine includes carbon that builds up on the top side of the piston, metal shavings from the wear of engine parts or dirt entering through the oil fill port.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS 8. Because the oil absorbs the abrasive particles, the engine components that are immersed in oil will show definite signs of abrasive ingestion especially around the connecting rod and main bearing journals. See Figure 11.6. Insufficient lubrication The bearing surfaces in an engine are not smooth.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS The hall mark of a lubrication failure is the presence of discoloration and/or metal transfer on all friction surfaces within the engine. See Figure 11.8. Engine Overspeed The MTD engine is designed for a maximum speed of 3600 rpm. When the governor is unable to control the engine rpm the engine can accelerate past the safe maximum speed. Discoloration When an engine runs beyond its designed speed a few things happen: 1.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS Overheated This warping of the head allows the head gasket to leak. A leaking head gasket allows the compressed gases in the engine to escape, lowering the compression in the engine and hurting engine performance. As the cylinder head cools, it shrinks back down to its normal size, but there will still be some warpage of the head. See Figure 11.11. The MTD engines are air cooled engines.
For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS Mechanical Breakage/ Wear Detonation/preignition Sometimes an engine fails because a part breaks. There are generally three causes of a broken part, outside of the previously discussed engine failures. They are abuse, wear, and manufacturing defects. Detonation is the undesirable condition of the fuel spontaneously combusting the combustion chamber prior to the spark plug firing.
