MTD 61 Series Shop Manual
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MTD 61 Series Shop Manual

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See also: Professional Shop Manual
Professional Shop Manual
61, 65 and 70 Series Vertical 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. Untrained or inexperi-
enced individuals should seek the assistance of an experienced and trained professional. Read, understand, and follow all
instructions and use common sense when working on power equipment. This includes the contents of the product's Oper-
ators Manual, supplied with the equipment. No liability can be accepted for any inaccuracies or omission in this publication,
although care has been taken to make it as complete and accurate as possible at the time of publication. However, due to
the variety of outdoor power equipment and continuing product changes that occur over time, updates will be made to these
instructions from time to time. Therefore, it may be necessary to obtain the latest materials before servicing or repairing a
product. The company reserves the right to make changes at any time to this publication without prior notice and without
incurring an obligation to make such changes to previously published versions. Instructions, photographs and illustrations
used in this publication are for reference use only and may not depict actual model and component parts.
© Copyright 2013 MTD Products Inc. All Rights Reserved
MTD Products Inc. - Product Training and Education Department

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Summary of Contents for MTD 61 Series

  • Page 1 Instructions, photographs and illustrations used in this publication are for reference use only and may not depict actual model and component parts. © Copyright 2013 MTD Products Inc. All Rights Reserved MTD Products Inc. - Product Training and Education Department...

  • Page 3: Table Of Contents

    Table of Contents Chapter 1: Introduction Professional Service Manual Intent ..............1 Safety .........................1 Fasteners ......................3 Assembly instructions ..................3 Model and serial number ................... 5 Maintenance ......................5 Spark plugs ......................6 Air filter .......................7 Oil type and capacity ..................8 Changing the oil ....................10 Fuel system .....................11 Servicing the fuel system .................11 Fuel filter ......................12...
  • Page 4 Chapter 4: The Fuel System and Governor Fuel Lines ......................37 Inspect the fuel lines ..................37 Inspecting the fuel ....................37 Test fuel for alcohol ..................38 The fuel filter ....................38 Fuel tank vent ....................39 The fuel tank ....................40 Evaporative (EVAP) emissions system ............43 Troubleshooting the EVAP system ..............46 Roll over valve vent ..................47 Charcoal canister .....................49...
  • Page 5 Chapter 7: Ignition System Troubleshooting the ignition system ..............85 Troubleshooting the stop switch ..............85 About the spark plug ..................91 Cleaning the spark plug ...................91 Inspection of the spark plug ................91 Spark plug removal ..................91 Ignition module ....................92 Module removal ....................92 Installing the module and setting the air gap ...........

  • Page 7: Chapter 1: Introduction

    • Common sense in operation and safety is assumed. • In no event shall MTD be liable for poor text interpretation or poor execution of the procedures described in the text. • If the person using this manual is uncomfortable with any procedures they encounter, they should seek the help of a qualified technician or MTD Technical Support.
  • Page 8 61, 65 and 70 Series Vertical Shaft Engines • Be prepared in case of emergency: ! CAUTION ! CAUTION Keep a fire extinguisher nearby Keep a first aid kit nearby Keep emergency contact numbers handy • Replace any missing or damaged safety labels on shop equipment. •...

  • Page 9: Fasteners

    Introduction Fasteners • 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. • If a fastener has a locking feature that has worn, replace the fastener or apply a small amount of releas- able thread locking compound such as Loctite®...
  • Page 10 61, 65 and 70 Series Vertical Shaft Engines MTD Vertical Engine Model Designators 1 P 6 1 M U A Major Revision Starter/Alternators 1=Recoil start Change 2=Electric start (12V) 3=E. start/alt. 18W 4=E. start/alt. 3A/5A 5= AutoChoke/ Recoil Compliance 6= AutoChoke/Electric Start...

  • Page 11: Model And Serial Number

    Introduction Model and serial number The model and serial number can be found on a white sticker with a bar code. The sticker is usually located between the dipstick and the muffler. See Figure 1.1. Model /serial number Dipstick Muffler Figure 1.1 NOTE: The serial number will always start with the model number.

  • Page 12: Spark Plugs

    Cleaning the spark plug: NOTE: MTD does not recommend cleaning spark plugs. Use of a wire brush may leave metal deposits on the insulator that causes the spark plug to short out and fail to spark. Use of abrasive blast for cleaning may cause damage to ceramic insulator or leave blast media in the recesses of the spark plug.

  • Page 13: Air Filter

    The second is an oval foam filter. See Figure 1.3. • Air filters used on the MTD engine are designed to prevent particles larger than 3-5 micron from passing through into the engine.

  • Page 14: Oil Type And Capacity

    61, 65 and 70 Series Vertical Shaft Engines Oil type and capacity The recommended oil for MTD engines is an SAE 10W-30 oil with an SM API rating or better. The oil capacity is 17.0- 20.3 fl.oz (0.5-0.6 liters). •...
  • Page 15 Introduction NOTE: There are two types of dip sticks that can be found on MTD engines; a threaded dip stick that was used on older engines and a quarter turn dip stick that is used on engines currently being produced.

  • Page 16: Changing The Oil

    61, 65 and 70 Series Vertical Shaft Engines Changing the oil NOTE: If the engine has been running, allow the engine to cool before doing any mainte- Siphon nance work. NOTE: The oil should be changed after the first 5 hours of operation and every 25 hours there after.

  • Page 17: Fuel System

    Introduction Fuel system What you should know about fuel. Most of the fuel presently available in North America is oxygenated to some extent. This is commonly done through the addition of ethanol. Most engines offered for sale on outdoor power equipment in the North American markets are designed to tolerate no more than 10% ethanol by volume Ethanol is hygroscopic, meaning it absorbs water.

  • Page 18: Fuel Filter

    61, 65 and 70 Series Vertical Shaft Engines Fuel filter Some of the early engines were equipped with a Fuel Filter fuel filter placed between the fuel tank and the car- buretor. See Figure 1.10. Figure 1.10 New style Currently the engines are equipped with a fuel filter installed in the fuel tank where the fuel line con- nects.

  • Page 19: Valve Lash

    Introduction Valve lash 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:.
  • Page 20 61, 65 and 70 Series Vertical Shaft Engines 0.004” feeler gauge Check valve lash between each valve stem and rocker arm using a feeler gauge. Intake valve lash (top valve) should be: See Figure 1.14. • “P70” series = 0.003” - 0.005” (0.08 - 0.12mm). •...

  • Page 21: Exhaust System

    Introduction Exhaust system 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 blockage. NOTE: A blocked muffler will result in poor performance. If a muffler is completely blocked, the engine may not start.
  • Page 22 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 23: Definitions

    Also check attachments for damage and make sure they are firmly mounted. Steps to troubleshooting NOTE: The steps and the order of the steps that follow are a suggested approach to troubleshooting the MTD engine. The technician does not necessarily have to follow them as described in this chapter.
  • Page 24 61, 65 and 70 Series Vertical Shaft Engines IV. Unusual exhaust tone There are tools that the technician can use in order to define the problem, such as: Interview the customer. 1a. Get a good description of their complaint. 1b. If it is an intermittent problem, verify what conditions aggravate the problem as best as possible. 1c.

  • Page 25: Identify Factors That Could Cause The Problem

    ASIC ROUBLESHOOTING Identify factors that could cause the problem This is the second step in the troubleshooting process. Crankshaft will not turn. A. Starter not working. This can be an electrical failure or a mechanical failure. The likely suspects are: A dead battery.
  • Page 26 61, 65 and 70 Series Vertical Shaft Engines 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 goes away at the same time the engine dies. II.
  • Page 27 ASIC ROUBLESHOOTING V. Makes unusual smoke when running a. Black smoke, usually heavy, usually indicates a rich air fuel mixture • Not enough air: air flow blockage or a partially closed choke. • Too much fuel: carburetor float or float valve stuck or metering / emulsion issues with the car- buretor.
  • Page 28 61, 65 and 70 Series Vertical Shaft Engines chirping noise. • Confirm with a compression test and leak-down test. e. Unusual exhaust tone Splashy or blatty • Splashy idle usually indicates a slight rich condition. • May indicate an exhaust blockage, usually slightly muffled. Backfire •...

  • Page 29: Repairing The Problem

    ASIC ROUBLESHOOTING Repairing the problem The third step in the troubleshooting process is to repair the problem. This step consists of: A. Form a diagnosis by using all of the information gathered from the troubleshooting that was performed. B. Physically perform the repair. The fourth, and hopefully final, step in the troubleshooting process is the follow through.

  • Page 30: Prime Test

    61, 65 and 70 Series Vertical Shaft Engines Prime test To perform a prime test: Prime the engine through the carburetor throat using a squirt bottle, filled with clean fresh gasoline. Make sure the throttle is in the run position. Attempt to start the engine.
  • Page 31 ASIC ROUBLESHOOTING Compare the results to the following chart. Leak-down Testing Results Symptom Possible cause Air escaping from Worn cylinder or piston rings. the breather Possible blown head gasket Air escaping from Leaking exhaust valve the exhaust Air escaping from Leaking intake valve the carburetor Gauge reading...

  • Page 32: Compression Test

    61, 65 and 70 Series Vertical Shaft Engines Compression test To perform a compression test: NOTE: Compression should be in the range of 55 - 85 PSI (3.8 - 5.9 Bar). • Disconnect the high-tension lead from the spark plug and ground it well away from the spark plug hole. •...

  • Page 33: Pcv Testing

    2.4. NOTE: Less than (between zero and -1”) (-2.54cm) of water is a typical reading. NOTE: Experimentation by MTD’s Training and Education Department has revealed the following character- istics of MTD engines: • A leaky PCV system will not build-up substantial case pressure.
  • Page 34 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 35: Chapter 3: Air Intake System

    YSTEM CHAPTER 3: AIR INTAKE SYSTEM Air filter MTD vertical shaft engines are equipped with one of Paper-pleated element two different air filters. The first is a rectangular paper pleated filter that may or may not have a foam pre-cleaner.

  • Page 36: Paper Air Filter Housings

    61, 65 and 70 Series Vertical Shaft Engines Paper filter with a snap fit door To access the air filter: Press down on both tabs See Figure 3.3.. Swing down the filter door. Tabs Remove the air filter. Install the filter by following the previous steps in reverse order.

  • Page 37: Foam Air Filter

    NTAKE YSTEM Foam air filter To access the air filter: Press in the tab on the air filter cover. See Figure 3.6. Press tab Figure 3.6 Swing open the filter cover. See Figure 3.7. Remove the air filter. Install by following the above steps in reverse order. Figure 3.7 Foam air filter housing To remove the air filter housing:...
  • Page 38 61, 65 and 70 Series Vertical Shaft Engines Disconnect the crankcase vent tube. See Figure 3.9. Disconnect the primer line. See Figure 3.9. Primer line Lift away the filter housing. crankcase vent tube Figure 3.9 The primer can be removed from the air filter hous- ing by squeezing together the two sets of barbs while pushing the primer out of the housing.

  • Page 39: Carburetor Insulator

    NTAKE YSTEM Carburetor Insulator To avoid personal injury or property damage, use extreme care in handling gasoline. Gaso- ! WARNING ! WARNING line is extremely flammable and the vapors are explosive. Serious personal injury can occur when gasoline is spilled on yourself and/or your clothes which can ignite. Wash your skin and change clothes immediately To remove/replace the carburetor insulator: Remove the air filter housing by following the previ-...
  • Page 40 61, 65 and 70 Series Vertical Shaft Engines 2d. Rotate the throttle arm until it meets the idle Governor rod speed screw, then pivot the carburetor slightly to disengage the 90 degree bend at the end of the governor rod. See Figure 3.14. Throttle arm Figure 3.14 2e.
  • Page 41 NTAKE YSTEM Insulator The insulator is sandwiched between two gaskets Bowl vent channel which are located between the carburetor and the cylinder head. See Figure 3.17. NOTE: The gaskets are different, and there is an orienta- tion to the insulator. Gasket: Insulator to carburetor Gasket: insulator...
  • Page 42 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 43: Chapter 4: The Fuel System And Governor

    NOTE: When working on the fuel systems, look at the whole system. A problem will rarely be isolated to one component. Fuel Line The fuel line used by MTD is GREENBAR . This is NBR intermediate layer NBR inner liner a multi-layer fuel line that meets the current EPA guide- lines.

  • Page 44: Inspecting The Fuel

    This results in less power for the engine. A 10% ethanol (E10) mix is acceptable for MTD engines. Anything higher than that will result in perfor- Figure 4.2 mance issues.

  • Page 45: The Fuel Filter

    YSTEM AND OVERNOR The fuel filter The fuel filter is located in the fuel tank. It can be removed New style and cleaned with a can of carb cleaner or replaced. See Figure 4.4. Old style Figure 4.4 NOTE: On some early production engines, an in-line filter was used.

  • Page 46: Fuel Tank Vent

    61, 65 and 70 Series Vertical Shaft Engines Fuel tank vent The fuel tank vent performs the important task of allow- Tank ing air into the fuel tank. As fuel is being used by the engine, the fuel level in the tank drops. The dropping fuel Cap liner / gasket level then creates a vacuum in the tank.

  • Page 47: The Fuel Tank

    YSTEM AND OVERNOR The fuel tank There are three fuel tanks available for the 61, 65 and 70 series engines: • The original bolt through the center tank. • The charcoal canister tank. • The slanted neck tank. When working around the fuel system, do not bring any sources of heat, spark, or open flame ! WARNING ! WARNING near the work area.
  • Page 48 61, 65 and 70 Series Vertical Shaft Engines Remove the bottom screw using a 10mm wrench. See Figure 4.10. Remove this screw Figure 4.10 Remove the top two screws and remove the tank. See Figure 4.11. Install the tank by following the previous steps in reverse order.

  • Page 49: Evaporative (Evap) Emissions System

    To reduce or eliminate the release of fuel vapors into the atmosphere, an evaporative (EVAP) emis- sions system is used. Starting with the 2008 season, an EVAP system has been offered in areas that require it. MTD has three systems that can be used: •...
  • Page 50 61, 65 and 70 Series Vertical Shaft Engines Charcoal canister system with the canister snapped into the tank This charcoal canister system consists of: • A charcoal canister Roll over valve • The fuel tank and cap Charcoal canister • A roll over valve vent •...
  • Page 51 YSTEM AND OVERNOR When the engine is running, the vacuum inside the carburetor insulator is used to draw the vapors out of the charcoal canister, temporarily enriching the fuel/ air mixture, and is used in the combustion process. See Figure 4.18. Charcoal canister Figure 4.18 Charcoal canister system with the canister snapped into the shroud...

  • Page 52: Troubleshooting The Evap System

    61, 65 and 70 Series Vertical Shaft Engines Troubleshooting the EVAP system NOTE: Troubleshooting a charcoal canister fuel cap is the same as troubleshooting a non-EVAP system. Symptom Cause Fuel leaking from the A blockage in the charcoal carburetor throat or canister or between the vents canister and the tank.

  • Page 53: Roll Over Valve Vent

    YSTEM AND OVERNOR Roll over valve vent To remove/replace the roll over valve: Disconnect the vacuum line. See Figure 4.21. Disconnect the vacuum line Figure 4.21 Gently pry the roll over valve out of the fuel tank. See Figure 4.22. Inspect the rubber grommet, replace if damaged.
  • Page 54 61, 65 and 70 Series Vertical Shaft Engines Testing the roll over valve The roll over valve vent has two functions. The first function is to vent the tank and the second function is to close off the vent if the tank is inverted. Test the roll over valve by: Remove the roll over valve by following the steps described above.

  • Page 55: Charcoal Canister

    YSTEM AND OVERNOR Charcoal canister To remove/replace the charcoal canister snapped into the tank: Remove the fuel tank by following the steps described in the Charcoal canister fuel tank section of this chap- ter. Remove the vacuum line that runs from the roll over valve to the charcoal canister.

  • Page 56: Manual Choke

    4.29. Figure 4.29 Autochoke The MTD engine uses a simple autochoke system that is similar to the old style air vane governors. When the engine is at rest a spring holds the choke in the closed position. See Figure 4.30.

  • Page 57: 1P61/1P65 Autochoke

    YSTEM AND OVERNOR When the engine starts, the air flow from the flywheel fan pushes on an air vane. the air vane in turn moves the Air flow choke lever, opening the choke. See Figure 4.31. Choke open Figure 4.31 1P61/1P65 Autochoke To remove/replace the air vane: NOTE: The choke linkage can be slightly bent to make...

  • Page 58: 1P70 Autochoke

    61, 65 and 70 Series Vertical Shaft Engines 1P70 Autochoke The 1P70 autochoke uses an air door that functions the same way as the air vane described earlier. NOTE: There is no choke linkage in this system, therefore there is no way to make adjustments for choke travel.

  • Page 59: Temperature Compensating Auto Choke

    YSTEM AND OVERNOR To install the air door, turn the blower housing upside down. Hold the air door in place while sliding in the rod. NOTE: Make sure the rod goes through all of the rod channels. See Figure 4.37. Rod channels Figure 4.37 Temperature compensating auto choke...

  • Page 60: Primer

    61, 65 and 70 Series Vertical Shaft Engines Primer Another way to enrichen the fuel air mixture for start- up is the primer. The primer is a simple pump that pressur- Primer Carburetor izes the float chamber, forcing fuel out the main nozzle. Primer See Figure 4.39.

  • Page 61: Carburetors

    YSTEM AND OVERNOR Squeeze the two sets of tabs together and push the primer out of the housing. See Figure 4.42. Install the primer by following the above steps in reverse order. Test run the engine before returning to service. Squeeze the barbs together, then push Figure 4.42...

  • Page 62: Disassembly And Rebuilding The Carburetor

    61, 65 and 70 Series Vertical Shaft Engines Disassembly and rebuilding the carburetor Bowl vent port Clamp off the fuel line to prevent fuel spillage and remove it. Remove the carburetor by following the steps described in Chapter 3: Air Intake and Filter. NOTE: There is a corresponding passage recessed into the mating surface where the throttle end of the Bowl vent...
  • Page 63 YSTEM AND OVERNOR NOTE: The float is not adjustable. Spring tension against Float the float valve begins to build from the horizontal position, putting progressively more pressure Compression between the tip of the valve and the seat. See Fig- spring ure 4.46.
  • Page 64 61, 65 and 70 Series Vertical Shaft Engines Emulsion air port: main jet NOTE: Fuel enters the central column through a Emulsion tube port about 1/2” (1cm) from the bottom, to help prevent the ingress of any residue in Main jet the bottom of the bowl.
  • Page 65 YSTEM AND OVERNOR Air passage End view Examine the metering plug: See Figure 4.52. • Fuel, drawn from the central column via the long fuel feed leg, is metered by the brass orifice in the tip of the metering plug. •...
  • Page 66 61, 65 and 70 Series Vertical Shaft Engines Clean the carburetor body in an ultrasonic cleaner. NOTE: Traditional dips are not recommended. Rinse thoroughly. Dry the carburetor body using compressed air. Pre-installation adjustment: 13a. Tighten the idle speed screw until 1/8” (3 mm) of the screw is visible on the throttle arm side of the housing.

  • Page 67: Governor

    YSTEM AND OVERNOR Governor 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 Governor action the governor arm (pushing the throttle closed). See Figure 4.58.
  • Page 68 61, 65 and 70 Series Vertical Shaft Engines Governor shaft To remove or replace the governor shaft: Remove the engine from the unit. Remove the governor arm by following the previ- ously described steps. Remove the sump by following the steps described in Chapter 10: Disassembly.
  • Page 69 YSTEM AND OVERNOR Slide the governor shaft into the engine block from the inside of the engine. Carefully slide a new seal over the governor shaft and seat using a 1/4” deep well socket. See Figure Seal 4.63. Install the hair pin clip. Figure 4.63 10.

  • Page 70: Governor Cup And The Governor Gear

    61, 65 and 70 Series Vertical Shaft Engines Governor cup and the governor gear Remove these screws Remove the engine from the unit. Remove the sump by following the steps described in Chapter 10: Disassembly. Remove the two screws that hold the governor gear plate to the sump using a 10mm wrench.

  • Page 71: Chapter 5: Lubrication

    Lubrication CHAPTER 5: LUBRICATION Oil type and quantity The recommended oil for MTD engines is an SAE 10W-30 oil with an SM API rating or better. The oil capacity is 17.0- 20.3 fl.oz (0.5-0.6 liters). 14°F 32°F 50°F 68°F 86°F 104°F...

  • Page 72: Oil Dipstick

    Oil dipstick NOTE: There are two types of dip sticks that can be found on MTD engines; a threaded dip stick that was used on older engines and a quar- ter turn dip stick that is used on engines cur- rently being produced.

  • Page 73: Dip Stick Tube Removal

    Lubrication Dip stick tube removal Some MTD engines come with a dip stick tube, depending on the application. See Figure 5.4. To remove/replace the dip stick tube: Remove the dip stick. Remove the screw at the top of the dip stick tube.

  • Page 74: Lubrication System

    61, 65 and 70 Series Vertical Shaft Engines Lubrication system MTD uses a splash lube system for it’s vertical shaft engines. The governor gear has paddles on it that “splashes” oil around the inside of the engine. See Figure Governor 5.6.

  • Page 75: Pcv

    Lubrication The PCV valve is located under the flywheel and allows Dimple the crankcase pressure to escape. The function and test procedures for the PCV is covered in Chapter 2: Basic chamber Troubleshooting. cover To service the PCV: Remove the flywheel by following the steps described in the Chapter 7: Ignition System.
  • Page 76 61, 65 and 70 Series Vertical Shaft Engines Inspect the disc for any signs of dirt, damage or Disc leaking. Port to Inspect the folded wire mesh in the chamber. See crankcase Figure 5.12. Port to PCV hose Folded wire mesh Figure 5.12 Inspect the oil drain-back port.
  • Page 77 Lubrication NOTE: The new breather valve is a rubber umbrella valve, Umbrella valve that is pressed into an aluminum disk. See Figure 5.15. NOTE: The valve is not serviceable. Trying to remove the rubber valve will cause the bottom of the valve to break off.
  • Page 78 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 79: Chapter 6: Starter And Charging Systems

    Starters CHAPTER 6: STARTER AND CHARGING SYSTEMS Recoil Starter Removal To remove recoil assembly from the engine: Engine shroud NOTE: Some engines are not equipped with an engine shroud, depending on the application. If the engine Mounting screws does not have an engine shroud, skip to step 5. If the engine is installed on a mower, loosen the wing- nut, that secures the starter rope eyelet to the han- dlebars, enough to provide clearance for the starter...

  • Page 80: Starter Cup

    61, 65 and 70 Series Vertical Shaft Engines Starter Cup The starter cup can either be cast into the flywheel or Starter cup be a steel cup that is bolted to the flywheel depending on (cast into flywheel) the application. Inspect the inside of the starter cup.

  • Page 81: Starter Rope

    Starters Starter Rope The most common failure mode for most recoil assem- Recoil assembly, blies is a broken rope. See Figure 6.5. removed from mower NOTE: If the spring was not damaged when the recoil Starter cord sprung back, It is possible to simply remove the Knot remnants of the old rope.
  • Page 82 61, 65 and 70 Series Vertical Shaft Engines Rope-return tension may NOTE: If starter rope tension needs to be adjusted, be increased by winding there is room between the recoil housing and the the rope and pulley pulley to wind-on more tension. See Figure 6.8. counter clockwise.

  • Page 83: Starter Pulley And Recoil Spring

    Starters Starter pulley and recoil spring The recoil spring is nested within the starter pulley and both parts are assembled as a single part number. Pressure plate Eye protection should be worn if Shoulder screw ! CAUTION ! CAUTION the starter pulley is to be removed. If damage is suspected, the recoil may be disassem- bled by: Remove the starter by following the steps described...
  • Page 84 61, 65 and 70 Series Vertical Shaft Engines NOTE: If the spring is undamaged, but has been removed from the pulley, the spring may be re-wound. Engage the hook in the end of the spring with the slot in the outer lip of the recess that the spring fits in, and wind the spring into the recess in a counter-clockwise direction.

  • Page 85: Electric Starter Relay

    Starters Electric starter relay The electric starter on the MTD engine uses a relay that acts as a remote switch instead of a solenoid, which would also move the bendix gear out to engage the fly- wheel. The bendix gear on this starter will move to engage Mounting bolt the flywheel by centrifugal force.

  • Page 86: Testing The Starter Relay

    61, 65 and 70 Series Vertical Shaft Engines Testing the starter relay To test the starter relay: Unplug the starter harness. Unbolt the relay from the engine. Starter relay Disconnect the two 12 AWG wires from the bottom ground lead of the relay.
  • Page 87 Starters Connect the positive side of the power source to the terminal that has the piggy back wire on it. See Fig- ure 6.18. Piggy back wire Figure 6.18 Reconnect the DMM with it still on the Ohms () scale. See Figure 6.19. NOTE: The DMM should read less than 0.2 Ohms ().

  • Page 88: Electric Starter

    61, 65 and 70 Series Vertical Shaft Engines Electric starter To remove/replace the electric starter: Disconnect the engine harness. Remove the screw that secures the starter relay and oil dip stick tube to the engine block using a 10mm wrench. See Figure 6.20. Remove this screw Figure 6.20...

  • Page 89: Schematic

    Starters Schematic...
  • Page 90 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 91: Chapter 7: Ignition System

    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 efficiently ignite the fuel/air mixture. The steps in troubleshooting the ignition system are: Examine the spark plug(s) by following the steps described in the spark plug section of this chapter.

  • Page 92: Troubleshooting The Stop Switch

    61, 65 and 70 Series Vertical Shaft Engines Troubleshooting the stop switch NOTE: the stop switch could be mounted near the carburetor or if the engine is equipped with an engine brake, the stop switch will be located on the engine brake. The switch is designed to ground out the module.
  • Page 93 Ignition System 7e. If further investigation is required, remove the recoil assembly by following the steps described in Chapter 6: Starter. Visually trace the wire from the stop switch to the connector on the module, and inspect the wire for any damaged insulation or potential contact with ground.
  • Page 94 61, 65 and 70 Series Vertical Shaft Engines 9c. Simple spark-testers are readily available and inexpensive. Thexton Part # 404 is available Instructions on from a variety of retailers, and similar units are back of package available form other manufacturers. See Figure 7.8.
  • Page 95 Ignition System 10. Resistance in the primary windings of the ignition module, measured between the spade terminal and the laminations, was observed to be in the 550-650  range. See Figure 7.11. Probe to laminations Probe to stop switch spade terminal Figure 7.11 10a.
  • Page 96 61, 65 and 70 Series Vertical Shaft Engines NOTE: Intermittent failure requires tests for voltage and resistance to be made when the engine is cold, and again when it is hot. Typical cus- tomer complaint: “It stops after I mow for 10 minutes and I can’t get it to re-start”.

  • Page 97: About The Spark Plug

    Ignition System About the spark plug • The spark plug is a F6RTC, part #951-10292, gapped to 0.024” - 0.031” (0.6 - 0.8 mm). NOTE: The X65 engine uses a F5RTC, part #951-14437, gapped to 0.024” - 0.031” (0.6 - 0.8 mm). •...

  • Page 98: Ignition Module

    61, 65 and 70 Series Vertical Shaft Engines Ignition module The ignition system is either a capacitive discharge or a inductive discharge magneto, depending on the application, contained in a single module. • The capacitive discharge has a three leg design. •...

  • Page 99: Installing The Module And Setting The Air Gap

    Ignition System Installing the module and setting the air gap NOTE: If just setting the air gap, loosen the module mounting screws first then follow the same steps as described below. Rotate the flywheel so that the magnets are away from where the module is mounted.

  • Page 100: Engine Brake And Stop Switch (If Equipped)

    61, 65 and 70 Series Vertical Shaft Engines Engine brake and stop switch (if equipped) The stop switch and brake (for lawn mower applications) must be able to stop the blade from rotating within 3.0 sec- onds after the release of the safety bail, per ANSI B71.1-2003 standard. NOTE: The brake should be replaced when the thickness of the pad is less than .25”...

  • Page 101: Adjusting The Brake Assembly (If Equipped)

    Ignition System Adjusting the brake assembly (if equipped) Disconnect and ground the spark plug wire. Remove the recoil assembly and blower housing by following the steps described in Chapter 6: Starter. Slightly loosen the two bolts that holds the brake Screw: pivot point assembly in place using a 10mm wrench.

  • Page 102: Flywheel

    61, 65 and 70 Series Vertical Shaft Engines Flywheel There are two types of flywheels available for the MTD engine. An aluminum flywheel and a 3-piece cast iron fly- Cast iron flywheel wheel. See Figure 7.22. NOTE: The procedure for removing the flywheel is the same for both aluminum and cast iron flywheels.
  • Page 103 Ignition System NOTE: If equipped with an engine brake, clamp off the brake using a spring clamp. See Figure 7.25. Figure 7.25 Remove the flywheel by applying a sharp blow to the crankshaft using a brass drift punch and a hammer while gently prying with a prybar.
  • Page 104 61, 65 and 70 Series Vertical Shaft Engines Starter cup protrusion IMPORTANT: The taper in flywheel and the on the crankshaft must be clean and dry. The flywheel is held in place by the friction fit between the flywheel and the crankshaft, not the key. The key is only to guide the flywheel to the proper position until it is torqued down.

  • Page 105: Chapter 8: Exhaust

    NOTE: A blocked muffler will result in poor performance. If a muffler is completely blocked the engine may not start. The MTD engine uses one of two different mufflers; a standard muffler covered here or a catalytic converter muf- fler that will be covered later in this chapter.
  • Page 106 61, 65 and 70 Series Vertical Shaft Engines Slide the muffler off of the studs. See Figure 8.3. Figure 8.3 NOTE: The muffler gasket extends well beyond the port, to act as a heat shield and guides cool- ing air between the muffler and the cylinder. See Figure 8.4.

  • Page 107: Catalytic Converter Muffler

    Exhaust Catalytic converter muffler The CARB (California) compliant engines use a cata- lytic converter muffler. This muffler also has an air injector to help with the catalytic reaction in the muffler. The Cata- lytic muffler can be identified by the presence of this air injector.
  • Page 108 61, 65 and 70 Series Vertical Shaft Engines To service/replace the air injector: Remove the two screws that secure the air injector using an 8mm wrench. See Figure 8.7. Remove these screws Figure 8.7 Remove the two screws that secure the screen Screen cover cover using a #2 Phillips screw driver.

  • Page 109: Chapter 9: Cylinder Head

    Cylinder head CHAPTER 9: CYLINDER HEAD The Cylinder head of the MTD engine can be removed without removing the engine from the application. To remove the cylinder head: NOTE: If possible, It is recommended that the machine be positioned on the bench so that the cylinder head is vertical for removal.
  • Page 110 61, 65 and 70 Series Vertical Shaft Engines Jam nut Loosen the jam nuts and fulcrum nuts that secure the rocker arms using a 10mm wrench and a 14mm Head bolts wrench. See Figure 9.3. Pivot the rocker arms aside, or remove them com- pletely, and remove the push rods.
  • Page 111 Cylinder head NOTE: Current production has the dowels on a diagonal. See Figure 9.6. 12. Carefully clean all sealing surfaces of all gasket resi- due. Do not scratch the sealing surfaces. NOTE: Make a visual inspection of the valves and cylinder bore to confirm the initial diagnosis.

  • Page 112: Valves

    61, 65 and 70 Series Vertical Shaft Engines 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.
  • Page 113 Cylinder head Inspect the valve seat. See Figure 9.10. • Valve seats are 45 degrees, with a 15 degree top- ping cut and a 75 degree narrowing cut. • Seat width should be 0.043” - 0.050” (1.1 - 1.3 mm) with a margin of 0.024”...
  • Page 114 61, 65 and 70 Series Vertical Shaft Engines...

  • Page 115: Chapter 10: Crankshaft, Piston And Connecting Rod

    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 to the component being removed.
  • Page 116 61, 65 and 70 Series Vertical Shaft Engines NOTE: The thrust washer should be removed when the sump is removed. Cam shaft Remove the camshaft. See Figure 10.2. NOTE: Align the timing marks to allow easier removal of the cam shaft and to help protect the Compression compression relief from damage.
  • Page 117 Crankshaft, piston and connecting rod Place a match mark here 13. Remove the connecting rod cap using a 10mm wrench. See Figure 10.5. NOTE: Match mark the connecting rod cap and the con- necting rod so that they can be reassembled in the proper orientation.

  • Page 118: Crank Shaft Inspection

    61, 65 and 70 Series Vertical Shaft Engines Remove the crank shaft. See Figure 10.8. Lift up on crank shaft Figure 10.8 Crank shaft inspection Inspect the crank shaft journals for galling, scoring, pitting or any other form of damage. Measure the journals at the bearing contact points using a vernier caliper or a micrometer.

  • Page 119: Piston Inspection

    Crankshaft, piston and connecting rod Piston Inspection Clean the piston and remove all carbon from the rings and ring groves. Insert one ring into the cylinder. Push it down about Piston ring one inch from the top. See Figure 10.11. Measure the end gap with a feeler gauge and com- pare to the chart at the end of this chapter.

  • Page 120: Connecting Rod Inspection

    61, 65 and 70 Series Vertical Shaft Engines Measure the distance between the ring and the ring land using a feeler gauge and compare the mea- surement to the chart at the end of this chapter. See Feeler gauge Figure 10.14. Figure 10.14 Connecting rod inspection Inspect the connecting rod for cracks or any signs of...

  • Page 121: Cylinder Inspection

    Crankshaft, piston and connecting rod Cylinder inspection Measure the cylinder bore Clean and inspect the cylinder, inside and out. NOTE: If there is any sign of damage, especially cracked cooling fins, short block the engine. NOTE: Take two measurements of the cylinder bore 90 degrees apart at the top, bottom and middle of the cylinder.

  • Page 122: Bearings

    61, 65 and 70 Series Vertical Shaft Engines NOTE: On the X65 series of engines, the cylinder is manufactured using a special machining process. This process does not leave a cross hatch that is normally seen in most engines. As the engine breaks in, the cylin- der will develop a smooth, dull finish.

  • Page 123: Reassembly

    Crankshaft, piston and connecting rod Reassembly Clean the cylinder 1a. Remove all gasket material from all mating sur- faces. 1b. Clean the cylinder and sump. Oil seals Troy-Bilt seal driver 2a. Install a new oil seal in the cylinder block. NOTE: A piece of 1”...
  • Page 124 61, 65 and 70 Series Vertical Shaft Engines 4d. Tap the piston through the ring compressor into the cylinder using a wooden hammer handle. See Figure 10.25. Tap piston with hammer NOTE: Make sure the crankshaft journal is at BDC handle (bottom dead center) to prevent damage from the connecting rod.
  • Page 125 Crankshaft, piston and connecting rod Install the cam shaft by: 6a. Pre-lube the cam shaft with clean 10W-30 motor oil or engine assembly lube. 6b. Rotate the crank shaft until the timing mark points to the tappets. Insert the cam shaft while aligning the timing marks.
  • Page 126 61, 65 and 70 Series Vertical Shaft Engines Install the sump by: 10a. If removed, install the governor gear and cup by following the steps described in Chapter 4: Fuel system and Governor. 10b. Place a new gasket on the sump, let the align- Governor ment dowels hold it in place.

  • Page 127: Engine Specifications Chart

    Crankshaft, piston and connecting rod Engine specifications chart New Min New Max Service Limit Inch Metric Inch Metric Inch Metric Displacement 122.7 cc (7.5^3) 139.4 cc(8.5^3) 159.3 cc (9.7^3) 173.2 cc (10.6^ 3) Bore (new) 2.402 61.015 2.403 61.025 2.409 61.182 2.559 65.005...
  • Page 128 61, 65 and 70 Series Vertical Shaft Engines New Min New Max Service Limit Inch Metric Inch Metric Inch Metric 0.983 24.970 0.984 24.985 0.979 24.864 0.999 25.370 0.999 25.385 0.995 25.262 0.983 24.970 0.984 24.985 0.979 24.864 Crank pin diameter 1.023 25.984 1.023...
  • Page 129 Crankshaft, piston and connecting rod New Min New Max Service Limit Inch Metric Inch Metric Inch Metric Connecting rod to crank pin running clearance 0.001 0.017 0.001 0.036 0.002 0.057 0.001 0.017 0.001 0.036 0.002 0.057 0.001 0.017 0.001 0.036 0.002 0.057 0.001...
  • Page 130 61, 65 and 70 Series Vertical Shaft Engines New Min New Max Service Limit Inch Metric Inch Metric Inch Metric 0.551 14.000 0.552 14.018 0.553 14.048 0.551 14.000 0.552 14.018 0.553 14.048 0.551 14.000 0.552 14.018 0.553 14.048 Intake lobe height 1.085 27.550 1.093...
  • Page 131 Crankshaft, piston and connecting rod New Min New Max Service Limit Inch Metric Inch Metric Inch Metric Intake valve lash 0.004 0.100 0.006 0.150 0.004 0.100 0.006 0.150 0.004 0.100 0.006 0.150 0.003 0.080 0.005 0.120 Exhaust valve lash 0.006 0.150 0.008 0.200...

  • Page 132: Engine Torque Values Chart

    61, 65 and 70 Series Vertical Shaft Engines Engine torque values chart Fastener Torque Blower housing studs 89 in lbs (10 Nm) 89 in lbs (10 Nm) 89 in lbs (10 Nm) 89 in lbs (10 Nm) Breather cover 27 - 35 in lbs 27 - 35 in lbs 27 - 35 in lbs 27 - 35 in lbs...

  • Page 133: Chapter 11: Failure Analysis

    Failure Analysis CHAPTER 11: FAILURE ANALYSIS A properly maintained engine will provide years of service. Occasionally an engine will fail. An important part of working on engines is being able to recognize the root cause of engine failures. 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.
  • Page 134 61, 65 and 70 Series Vertical Shaft Engines When particles enter the combustion chamber, the Cross hatch polished off up and down motion of the piston grinds the parti- cles into the side of the cylinder walls and damages the cylinder wall, piston and piston rings. This can be identified by the scoring along the verti- cal axis of the piston and cylinder wall or the cross hatch on the cylinder wall being worn off.
  • Page 135 Failure Analysis Because the oil suspends the particles, the engine components that are immersed in oil will show defi- nite signs of abrasive ingestion especially around the connecting rod and main bearing journals. See Figure 11.5. NOTE: Abrasives that are trapped in the oil will cause the lower portion of the combustion chamber to wear- ing more than the upper portion.
  • Page 136 61, 65 and 70 Series Vertical Shaft Engines Insufficient lubrication The bearing surfaces in an engine are not smooth. The machining processes used to make the engine parts, leave little peaks and valleys that are only visible under a microscope. These peaks are called asperities. As the engine breaks in, the asperities break off leaving plateaus that become the bearing surface.
  • Page 137 This phenomenon is unique to MTD vertical shaft engines. If there is a claim shell pattern, similar to the one circled in Figure 11.9, The engine experi- enced a lack of lubrication failure.
  • Page 138 61, 65 and 70 Series Vertical Shaft Engines Engine Overspeed The MTD engine is designed for a maximum speed of 3300 rpm. When the governor is unable to control the engine rpm, the engine can accelerate past the safe maximum speed.
  • Page 139 Overheated The MTD engines are air cooled engines. Because of this, cleanliness of the engine is very important to the life of the engine. Dirt, grass and sludge all form an insulating layer on the engine. This will trap the heat in the engine and cause it to over heat.

  • Page 140: Detonation/Pre-Ignition

    61, 65 and 70 Series Vertical Shaft Engines Mechanical Breakage/ Wear 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. Bent blade A very common sign of an abused engine is a bent crank shaft.
  • Page 142 MTD Products Inc - Product Training and Education Department FORM NUMBER - 769-03354-02 12/2013...

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