MTD 61Series Professional Shop Manual
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MTD 61Series Professional Shop Manual

Horizontal shaft engines
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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. 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 2007 MTD Products Inc. All Rights Reserved
MTD Products Inc - Product Training and Education Department
FORM NUMBER - 769-04015
04/2008
www.mymowerparts.com

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Summary of Contents for MTD 61Series

  • 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 2007 MTD Products Inc. All Rights Reserved MTD Products Inc - Product Training and Education Department...
  • Page 2 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 www.mymowerparts.com...

  • Page 3: Table Of Contents

    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 ........................3 Spark plugs .........................3 Air filters..........................4 Oil type and capacity ......................5 Changing the oil........................
  • Page 4 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 ........................27 To test the cap vent ......................27 The fuel filter ........................27 Inspect the fuel lines: ......................28 The fuel tank ........................
  • Page 5 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 ...................52 The module ........................53 Module removal ........................54 Installing the module and setting the air gap ..............55 Flywheel ..........................55 About the spark plug ......................56 Cleaning the spark plug ....................56...
  • Page 6 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 www.mymowerparts.com...

  • Page 7: Chapter 1: Introduction

    In many cases, both will be • In no event shall MTD or Cub Cadet be liable for used so that the manual is handy as a quick-reference for poor text interpretation, or poor execution of guide as well as a step-by-step procedure guide that the procedures described in the text.
  • Page 8 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 1 6 1 - S H A S ta rte r/A lte rn a to rs M a jo r R e v is io n...

  • Page 9: Maintenance

    Spark plugs and non-warrantable engine damage may result. The spark plug used in the MTD engine is a Inspection of the spark plug can provide indica- Torch model F6RTC gapped to .024”-.032” (.60- tions of the operating condition of the engine.

  • Page 10: Air Filters

    Air filters used on the MTD engine are designed to prevent particles larger than 5 microns from passing through into the engine.

  • Page 11: Oil Type And Capacity

    159 in-lbs (14-18 Nm) on installation. • Synthetic oil is a suitable alternative, but it does not extend service intervals. NOTE: MTD recommends the use of petroleum oil during the break in period to ensure the piston rings correctly break in. •...

  • Page 12: Fuel

    Dirty fuel can clog the carburetor and introduce abra- sive materials into the engine. To help prevent that, MTD engines are equipped with a fuel filter. The fuel fil- 12 mm wrench ter is part of the fuel tank nipple. See Figure 1.5.

  • Page 13: Valve Lash

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION Valve lash Remove the four bolts that secure the valve cover using a 10mm wrench, and remove the Valve lash is the clearance between the top of the valve cover from the engine. valve stem and the rocker arm.

  • Page 14: Spark Arrestor

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 Chapter 1: INTRODUCTION Intake valve lash (carburetor side) should be Double-check the clearance after tightening the .003”-.005” (.10 + .02mm). See Figure 1.10. jam nut, to confirm that it did not shift. Re-adjust if necessary.

  • Page 15: General Torque Specifications

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 INTRODUCTION General torque specifications size size Grade in-lbs ft-lbs Nm 1.2 10.5 21.7 36.6 in-lbs ft-lbs Nm 1.7 13.6 27.1 47.5 in-lbs ft-lbs Nm 2.9 24.4 47.5 82.7 10.9 in-lbs ft-lbs Nm 4.1 33.9 66.4...

  • Page 16: Chapter 2: Basic Troubleshooting

    NOTE: The steps and the order of the steps that follow are a suggested approach to trouble- There are tools that the technician can use in order to shooting the MTD engine. The technician does define the problem, such as: not necessarily have to follow them as described Interview the customer.

  • Page 17: Identify Factors That Could Cause The Problem

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Cleanliness of the equipment will indi- Identify factors that could cause the problem cate the level of care the equipment This is the second step in the troubleshooting process. has received.
  • Page 18 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING IV. Bent crankshaft (unrepairable) Starts, runs poorly V. Internal binding, crankshaft, connect- 3a. Starts, then dies ing rod or piston (unrepairable) Run the engine with a spark tester in- Crankshaft turns, no start.
  • Page 19 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 carbure- a. Check valve lash tor. b. Check compression b. White smoke, usually heavy c. Check leak down to identify the •...
  • Page 20 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING ing into play as the engine RPMs engine run artificially lean. cross the activation threshold. c. Skip This will have no ill effects on engine performance. • Usually ignition related. •...

  • Page 21: Repairing The Problem

    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 To perform a prime test: repair the problem. This step consists of: Prime the engine through the carburetor throat Form a diagnosis by using all of the information using a squirt bottle, filled with clean fresh gaso- gathered from the troubleshooting that was per-...

  • Page 22: Leak Down Test

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Leak-down test Connect tester to compressed air. A leak-down test is the preferred method to test the Adjust the regulator knob until the needle on the engine’s ability to compress the charge. It will also gauge is in the yellow or set area of the gauge.

  • Page 23: Compression Test

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 BASIC TROUBLESHOOTING Compression test 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 Possible causes •...

  • Page 24: Pcv Testing

    The cause of this oil burning can be mistaken for a worn-out engine, if proper diagnosis (compres- sion, leak-down, and case pressure) is not per- formed. Experimentation by MTD’s Training and Educa- tion Department has revealed the following char- acteristics of MTD engines: •...

  • Page 25: Chapter 3: Air Intake Systems

    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 Pull off the choke and throttle knobs. See Figure and chore performers. The differences between snow 3.2.
  • Page 26 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS Remove the screw that fastens the engine Work the engine shroud off of the carburetor shroud by the fuel tank using a #2 phillips screw studs. driver. See Figure 3.4. NOTE: Be careful to pop the primer line out of the notch that secures it while working the engine shroud off.

  • Page 27: Chore Engines

    Unhook the spark plug wire from the clip in the pleated-paper element or foam. A combination of the carburetor insulator. Slide the insulator off of the two are used on the MTD engine. See Figure 3.9. carburetor studs. See Figure 3.8. Both filters...

  • Page 28: Air Filter Base And Intake Elbow

    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 Press in on the tab in the air filter cover. See To remove the air filter base: Figure 3.10.

  • Page 29: Carburetor Insulator

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS Inspect the air intake gasket. Carburetor Insulator NOTE: The air intake gasket is a Vulcanized CAUTION: When working around the fuel sys- metal gasket. If the rubber is not ripped or tem, do not bring any sources of heat, spark, or deformed, it can be reused.
  • Page 30 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS 2b. Disconnect the throttle linkage and return Unhook the spark plug wire from the clip molded spring. See Figure 3.16. into the insulator plate. See Figure 3.18. Spark plug wire Throttle linkage Clip Return spring...
  • Page 31 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 AIR INTAKE SYSTEMS NOTE: An insulator block separates the carbu- retor 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.

  • Page 32: Chapter 4: The Fuel System And Governor

    This results in less power for the engine. NOTE: Fuel is the maintenance item most often A 10% ethanol (E10) mix is acceptable for MTD overlooked by consumers. A lot of fuel systems engines. Anything higher than that will result in perfor- problems are caused by bad gas or too much mance issues.

  • Page 33: Fuel Tank Vent

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Generally these kits involve mixing a measured amount To test the cap vent of water and gas together and seeing were the bound- Clean off the vent. ary layer is.

  • Page 34: Inspect The Fuel Lines

    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? Drain the tank. • Are they brittle? Disconnect the fuel line from the tank by follow- ing the steps described in the fuel filter section of NOTE: If the answer to any of the above is yes,...

  • Page 35: Choke

    THE FUEL SYSTEM AND GOVERNOR Choke NOTE: On snow engines with electric start, the MTD engines are equipped with a choke, a primer or starter switch mounting bracket is bolted to the both. If equipped with a manual choke, it must be fuel tank and will come off with the tank.

  • Page 36: Choke Linkage

    Primers The rod connecting the choke knob to the choke plate MTD engines use a dry bulb primer. This means that on the carburetor can be bent slightly to facilitate there is no fuel in the primer bulb. The primer works by adjustment.

  • Page 37: Carburetors

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR To replace the primer: Carburetors If the primer is bad, disconnect hose from the If diagnosis indicates a fuel problem, inspect the carbu- carburetor. retor. This is important even if problems are identified elsewhere in the fuel system..

  • Page 38: Disassembly And Rebuilding The Carburetor

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Disassembly and rebuilding the carburetor Remove the bowl bolt using a 10mm wrench. See Figure 4.15. 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.
  • Page 39 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Remove the pin that the float hinges on to Remove the main jet using a narrow-shank remove the float. straight blade screwdriver. See Figure 4.18. NOTE: The float is not adjustable. Spring ten- Main jet sion against the float valve begins to build from Bowl gasket...
  • Page 40 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Carefully pry out the metering plug using a small screwdriver. See Figure 4.21. NOTE: The main jet secures the emulsion tube in the central column of the carburetor. See Figure 4.19.
  • Page 41 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Start engine and check the idle RPM using a tachometer. NOTE: The pilot screw regulates how much of this pre-mixed fuel/air emulsion is allowed to NOTE: Idle speed: If applicable, is 1,800 RPM + enter the throat of the carburetor, to atomize 160 RPM, set using throttle stop screw.

  • Page 42: Governor

    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 To remove the governor arm from the governor shaft: the force applied by a spring (pulling the throttle open) Remove the fuel tank by following the steps and a flyweight mechanism within the engine applying described in the Fuel Tank section of this chap-...

  • Page 43: Governor Shaft

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Governor shaft Check the movement of the fly-weights and cap on the governor gear. To remove or replace the governor shaft: Install the shaft by following the above steps in Remove the engine from the equipment that it reverse order.

  • Page 44: Governor Cup And The Governor Gear

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 THE FUEL SYSTEM AND GOVERNOR Governor cup and the governor gear Slide the shaft out of the gear and cup. Figure 4.31. To remove or replace the governor gear and cup: Remove the engine from the unit.

  • Page 45: Chapter 5: Lubrication

    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 To check the oil level: American Petroleum Institute (A.P.I.) requirements for NOTE: Be sure to check the engine on a level service classification SG/SF.

  • Page 46: Dip Stick Tube Removal

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 LUBRICATION Dip stick tube removal Pull the dip stick tube out of the engine block and fuel tank. See Figure 5.6. To remove/replace the dip stick tube: Remove the dip stick. Remove the two screws securing the dip stick cover in place using a #2 phillips screw driver.

  • Page 47: Lubrication System

    The second oil passage runs along the bottom side of the cylinder. This is the oil return passage. As the name MTD uses a splash lube system for it’s horizontal shaft implies, it allows the oil collecting in the cylinder head engines.

  • Page 48: Positive Crankcase Ventilation Valve

    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 NOTE: The PCV valve is not serviceable. If it is function and test procedures for the PCV valve is cov- faulty, the valve cover must be replaced.

  • Page 49: Chapter 6: Starter And Charging Systems

    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 fly- wheel.

  • Page 50: Starter Rope

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Install a starter cup by placing it on the flywheel, Starter Rope with the dimple on the bottom of the starter cup The most common failure mode for most recoil assem- in the dimple in the flywheel.

  • Page 51: Starter Pulley And Recoil Spring

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Install the handle and handle insert on the loose Starter pulley and recoil spring end of the rope, again using a double half-hitch. The recoil spring is nested within the starter pulley and See Figure 6.5.
  • Page 52 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS 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 Torsion springs country, it makes economic sense to replace the complete assembly, in other areas labor rates...

  • Page 53: Electric Starter

    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 NOTE: Before condemning a starter make sure engine. It is powered by an extension cord that is to bench test it.

  • Page 54: Charging System

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Testing Charging system Description The charging system will produce AC and DC voltages. The rectifier for the DC voltage is inside of the stator Some engines are equipped with a charging system. and is not serviceable.

  • Page 55: Stator

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 STARTER AND CHARGING SYSTEMS Move the red (+) to the red wire of the charger Stator harness. See Figure 6.15. To remove/replace the stator: Remove and ground the spark plug wire. Remove the flywheel by following the steps Red wire described in Chapter 7: Ignition System.

  • Page 56: Chapter 7: Ignition System

    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 CAUTION: Never remove the spark plug and in the combustion chamber at the proper time to ignite hold it against the cylinder head to test for spark.

  • Page 57: Stop Switch

    When the throttle is all the way to the right (stop), the multimeter should read at or near All MTD horizontal engines that are in use in North 0.0Ω, indicating continuity. See Figure 7.3. America have a stop switch built into the throttle lever assembly.

  • Page 58: Remote (Ignition) Stop Switch

    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 Remove the muffler cover. Disconnect the two wires from the remote switch.

  • Page 59: The Module

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Set the multimeter to the ohms (Ω) scale. The module • If the multimeter shows continuity, replace the The coil in this ignition system is an inductive discharge module. magneto, contained in a single module.

  • Page 60: Module Removal

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM • At operating speed, the ignition should produce Module removal voltage approaching 12,000. See Figure 7.11. Unplug the spark plug. Remove the Heatbox (snow engines) and intake 1 reticle = 4,000 Volts waveform is elbow by following the steps described in Chap- 3 reticles tall...

  • Page 61: Installing The Module And Setting The Air Gap

    A sheared flywheel key will throw off the ignition timing. They are uncommon on the MTD engine. If one is Install the module. Do not tighten the module found, check for a bent crankshaft. To Remove and/or down.

  • Page 62: About The Spark Plug

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Inspect the key, keyway, and tapered mating sur- About the spark plug faces of the flywheel and crankshaft. See Figure • The spark plug is a Torch model F6RTC, gapped 7.16.

  • Page 63: Spark Plug Removal

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 IGNITION SYSTEM Spark plug removal Disconnect and ground the spark plug wire. Remove the spark plug using a 13/16” or 21mm wrench. A flexible coupling or “wobbly” exten- sion may help. See Figure 7.17. 13/16”...

  • Page 64: Chapter 8: Exhaust

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 EXHAUST CHAPTER 8: EXHAUST The exhaust system is a frequently overlooked compo- If The spark arrestor needs to be cleaned or replaced: nent of an engine. It is important to make sure the muf- Remove the four screws that retain the muffler fler is in good condition and free of debris and/or shield using a 8mm wrench and lift it off of the...

  • Page 65: To Remove/Replace The Muffler

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 EXHAUST The spark arrestor can be: • Replaced NOTE: The MTD engine uses a graphite exhaust gasket. It is not reusable and must be • Cleaned by mechanical means replaced every time the muffler nuts are loos- •...

  • Page 66: Snow Engines

    Clean all of the gasket material off of the cylinder screws head and the muffler (if reusing the muffler) NOTE: The MTD engine uses a graphite exhaust gasket. It is not reusable and must be Figure 3.6 replaced every time the muffler nuts are loos- ened.

  • Page 67: Chapter 9: Cylinder Head

    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 Remove the throttle lever by removing the two without removing the engine from the piece of equip- screws using a 8mm wrench.
  • Page 68 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD Remove the four screws securing the valve Remove the cylinder head bolts using a 12mm cover using a 10mm wrench. See Figure 9.4. wrench. See Figure 9.6. Cylinder head bolts Remove valve cover Figure 9.6...
  • Page 69 Figure 9.8. described in Chapter 1: Introduction. NOTE: MTD uses graphite head gaskets that Install the carburetor and air cleaner, using new have a bead of silicon on them. They are not gaskets, by following the steps described in reusable.

  • Page 70: Valves

    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 NOTE: The exhaust valve has a secondary not available as service parts. The valves and valve keeper on it. Press down on the valve keeper seats can be serviced by grinding and lapping or the and the secondary keeper will pop off, Then head can be replaced.
  • Page 71 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CYLINDER HEAD Inspect the valve seat. See Figure 9.13. Inspect the valve springs. NOTE: Valve spring free length should be at least 1.22” (28.5mm). Original length is 1.44” (36.6mm). Install the valves in the cylinder head by follow- ing steps 2 - 5 in reverse order.

  • Page 72: Push Rod Bushings

    Push rod bushings Remove the rocker studs. See Figure 9.15. The MTD engine has bushings for the push rods that Lift the push rod bushing plate out of the cylinder need to be replaced from time to time. An indication head.

  • Page 73: Chapter 10: Crankshaft, Piston And Connecting Rod

    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 Carefully slide the crank case cover off of the when disassembling an engine.
  • Page 74 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Remove the valve tappets. See Figure 10.3. Push the piston out of the cylinder. 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...

  • Page 75: Crank Shaft Inspection

    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 Measure the crankpin using a vernier caliper or available as service parts. The intent of this chapter is a micrometer.

  • Page 76: Piston Inspection

    NOTE: Typically there is a top and bottom profile rings and ring groves. to compression rings, But the compression rings on the MTD are symmetrical. See Figure 10.10. Clean the cylinder bore and remove all carbon. Insert one ring into the cylinder. Push it down about one inch from the top.

  • Page 77: Connecting Rod Inspection

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Connecting rod inspection Cylinder inspection Inspect the connecting rod for cracks or any Clean and inspect the cylinder, inside and out. signs of damage. NOTE: If there is any sign of damage, especially Install the rod cap and tighten to a torque of 106 cracked cooling fins, short block the engine.

  • Page 78: Bearings

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Compare the measurements to those that are Bearings listed in the chart at the end of the chapter. There are two bearings to inspect; a bearing in the Inspect the cylinder cross hatch.

  • Page 79: Reassembly

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Reassembly Clean the cylinder NOTE: Use an old piece of microfiche or a seal protector to protect the oil seal lip while inserting 1a. Remove all gasket material from all mating the crank shaft.
  • Page 80 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD 4c. Slide the connecting rod and piston into the bolts to a torque of 106 -124 in-lbs (12 - cylinder. 14Nm). See Figure 10.21. NOTE: The arrow on the piston must point towards the push rod cavity.
  • Page 81 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Using a seal protector, slide the crankcase cover on to the crank shaft. See Figure 10.23. Seal protector Figure 10.23 Gently rock the crank case cover until it seats fully against the cylinder block.

  • Page 82: Engine Specifications Chart

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 CRANKSHAFT, PISTON AND CONNECTING ROD Engine specifications chart Table 1: Specification 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) Service limits Bore maximum diameter 2.386”...

  • Page 83: Engine Torque Values Chart

    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 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)

  • Page 84: Chapter 11: Failure Analysis

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS CHAPTER 11: FAILURE ANALYSIS A properly maintained engine will provide years of ser- Abrasive particles that enter the engine through vice. Occasionally an engine will fail. An important part the intake system can be sand or dirt.
  • Page 85 For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS Particles that enter the intake system travel at Other sources of abrasives that get into the engine great speed and act like sand blasting media includes carbon that builds up on the top side of the inside the engine.

  • Page 86: Insufficient Lubrication

    For Discount White Outdoor Parts Call 606-678-9623 or 606-561-4983 FAILURE ANALYSIS Because the oil absorbs the abrasive particles, Insufficient lubrication the engine components that are immersed in oil The bearing surfaces in an engine are not smooth. As will show definite signs of abrasive ingestion a result of the machining processes to make the engine especially around the connecting rod and main parts, there are little peaks and valleys that are only...

  • Page 87: Engine Overspeed

    On most engine that would be about an inch below the wrist pin, but on the MTD engine it is at the wrist pin. The force on the connecting rod is greatest when the piston transitions from the upward Figure 11.8...

  • Page 88: Overheated

    This warping of the head allows the head gasket to leak. A leaking head gasket allows the compressed The MTD engines are air cooled engines. Because of gases in the engine to escape, lowering the compres- this, cleanliness of the engine is very important to the sion in the engine and hurting engine performance.

  • Page 89: Mechanical Breakage/ Wear

    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. Detonation is the undesirable condition of the fuel There are generally three causes of a broken part, out- spontaneously combusting the combustion chamber side of the previously discussed engine failures.

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