MTD 70 Series Especificações

Professional Shop Manual61/65/70 Series Horizontal Shaft Engines MTD Products Inc - Product Training and Education DepartmentFORM NUMBER - 769-0401504

Chapter 1: INTRODUCTION4Air filtersGenerally air filters come in two different types, a pleated-paper element, or a foam plastic, sometimes a combinat

INTRODUCTION5Oil type and capacity1. To check the oil, twist and remove the dip-stick from the engine. Clean the oil off of the tip of the dipstick. R

Chapter 1: INTRODUCTION6FuelGasolines currently on the market are not pure gas. Today’s fuels have alcohol and other additives in them to reduce emiss

INTRODUCTION7Valve lashValve lash is the clearance between the top of the valve stem and the rocker arm. The valve lash should be checked after the fi

Chapter 1: INTRODUCTION89. Intake valve lash (carburetor side) should be .003”-.005” (.10 + .02mm). See Figure 1.10.10. Exhaust valve lash (muffler si

INTRODUCTION9General torque specifications Maintenance Chartsize M4 M5 M6 M8 size M10 M12 M14 Grade 4.8 in-lbs 11 22 38 93 ft-lbs 16 27 43Nm

BASIC TROUBLESHOOTING10DefinitionsTroubleshooting - The act gathering information by pre-forming tests and direct observations.Diagnosis - A theory of

BASIC TROUBLESHOOTING11I. Cleanliness of the equipment will indi-cate the level of care the equipment has received.II. Make sure the engine and attach

BASIC TROUBLESHOOTING12IV. Bent crankshaft (unrepairable)V. Internal binding, crankshaft, connect-ing rod or piston (unrepairable)2. Crankshaft turns,

BASIC TROUBLESHOOTING13V. Low compressiona. Check valve lashb. Check compressionc. Check leak down to identify the source of the compression loss.VI

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BASIC TROUBLESHOOTING14ing into play as the engine RPMs cross the activation threshold. This will have no ill effects on engine performance.• Half-eng

BASIC TROUBLESHOOTING15Repairing the problemThe third step in the troubleshooting process is to repair the problem. This step consists of:1. Form a di

BASIC TROUBLESHOOTING16Leak-down testA leak-down test is the preferred method to test the engine’s ability to compress the charge. It will also show w

BASIC TROUBLESHOOTING17Compression testTo perform a compression test:NOTE: Compression should be in the range of 40-60 PSI (2.81-4.1 Bar).• Disconnect

BASIC TROUBLESHOOTING18PCV testingThe PCV valve is located in the valve cover and allows the crankcase pressure to escape.Leakage and blockage are the

AIR INTAKE SYSTEMS19MTD builds horizontal crank engines for snow blowers and chore performers. The differences between snow engines and chore engines

AIR INTAKE SYSTEMS207. Remove the screw that fastens the engine shroud by the fuel tank using a #2 phillips screw driver. See Figure 3.4.8. Remove the

AIR INTAKE SYSTEMS2112. Slide the carburetor off of the carburetor studs.NOTE: The choke linkage will come off with the carburetor.13. Unhook the spar

AIR INTAKE SYSTEMS22To service the air filter:1. Press in on the tab in the air filter cover. See Figure 3.10.2. Swing open the cover and lift it off

AIR INTAKE SYSTEMS236. Inspect the air intake gasket.NOTE: The air intake gasket is a Vulcanized metal gasket. If the rubber is not ripped or deforme

Chapter 1: Introduction ... 1Professional Shop M

AIR INTAKE SYSTEMS242b. Disconnect the throttle linkage and return spring. See Figure 3.16.NOTE: The carburetors are not inter-changeable from one en

AIR INTAKE SYSTEMS25NOTE: An insulator block separates the carbu-retor from the cylinder head. There is a gasket on each side of the insulator. See Fi

THE FUEL SYSTEM AND GOVERNOR26The function of the fuel system is to store, mix the fuel with air and deliver it to the combustion chamber. The fuel sy

THE FUEL SYSTEM AND GOVERNOR27Generally these kits involve mixing a measured amount of water and gas together and seeing were the bound-ary layer is.

THE FUEL SYSTEM AND GOVERNOR28Inspect the fuel lines• Are they cracked?• Are they clogged?• Are they brittle?NOTE: If the answer to any of the above i

THE FUEL SYSTEM AND GOVERNOR29NOTE: On snow engines with electric start, the starter switch mounting bracket is bolted to the fuel tank and will come

THE FUEL SYSTEM AND GOVERNOR30Choke linkageThe rod connecting the choke knob to the choke plate on the carburetor can be bent slightly to facilitate a

THE FUEL SYSTEM AND GOVERNOR31To replace the primer:4. If the primer is bad, disconnect hose from the carburetor.5. Remove the hose camp at the rear o

THE FUEL SYSTEM AND GOVERNOR32Disassembly and rebuilding the carburetor1. Clamp-off the fuel line to prevent fuel spillage, then disconnect the fuel l

THE FUEL SYSTEM AND GOVERNOR335. Remove the pin that the float hinges on to remove the float.NOTE: The float is not adjustable. Spring ten-sion again

Chapter 4: The Fuel System and Governor ...26Inspecting the fuel...

THE FUEL SYSTEM AND GOVERNOR34NOTE: The main jet secures the emulsion tube in the central column of the carburetor. See Figure 4.19.7. The throttle st

THE FUEL SYSTEM AND GOVERNOR35NOTE: The pilot screw regulates how much of this pre-mixed fuel/air emulsion is allowed to enter the throat of the carbu

THE FUEL SYSTEM AND GOVERNOR36GovernorThe engine speed is controlled by a balance between the force applied by a spring (pulling the throttle open) an

THE FUEL SYSTEM AND GOVERNOR37Governor shaftTo remove or replace the governor shaft:1. Remove the engine from the equipment that it powers.2. Remove t

THE FUEL SYSTEM AND GOVERNOR38Governor cup and the governor gearTo remove or replace the governor gear and cup:1. Remove the engine from the unit.2. R

LUBRICATION 39Oil type and quantityUse a quality motor oil certified to meet or exceed American Petroleum Institute (A.P.I.) requirements for service

LUBRICATION 40Dip stick tube removalTo remove/replace the dip stick tube:1. Remove the dip stick.2. Remove the two screws securing the dip stick cover

LUBRICATION 41Lubrication systemMTD uses a splash lube system for it’s horizontal shaft engines. The connecting rod has a dipper on it that “splashes”

LUBRICATION 42Positive crankcase ventilation valve The PCV valve is located inside the valve cover. The function and test procedures for the PCV valve

STARTER AND CHARGING SYSTEMS43Recoil Starter Removal To remove recoil assembly from the engine:1. Remove the three nuts that secure the recoil assembl

Chapter 7: Ignition System ... 50Troubleshooting the ig

STARTER AND CHARGING SYSTEMS443. Install a starter cup by placing it on the flywheel, with the dimple on the bottom of the starter cup in the dimple i

STARTER AND CHARGING SYSTEMS457. Install the handle and handle insert on the loose end of the rope, again using a double half-hitch.See Figure 6.5.8.

STARTER AND CHARGING SYSTEMS464. Inspect the pawls and torsion springs for wear and damage. See Figure 6.8.5. Carefully lift the spring and pulley out

STARTER AND CHARGING SYSTEMS47Electric starterThe electric starter is only available on the snow engine. It is powered by an extension cord that is pl

STARTER AND CHARGING SYSTEMS48Charging systemDescriptionSome engines are equipped with a charging system. The charging system consists of:• Alternator

STARTER AND CHARGING SYSTEMS498. Move the red (+) to the red wire of the charger harness. See Figure 6.15.9. The multimeter should read 17 - 26Vdc.10.

IGNITION SYSTEM50Troubleshooting the ignition systemThe purpose of the ignition system is to provide a spark in the combustion chamber at the proper t

IGNITION SYSTEM51Stop switchAll MTD horizontal engines that are in use in North America have a stop switch built into the throttle lever assembly. MTD

IGNITION SYSTEM52Remote (ignition) stop switchTo test the remote stop switch:1. Remove the muffler cover.2. Disconnect the two wires from the remote s

IGNITION SYSTEM538. Set the multimeter to the ohms (Ω) scale.• If the multimeter shows continuity, replace the module.• If the multimeter does not sho

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IGNITION SYSTEM54• At operating speed, the ignition should produce voltage approaching 12,000. See Figure 7.11.• At pull-over speed (~ 600 RPM), volta

IGNITION SYSTEM55Installing the module and setting the air gapNOTE: If just setting the air gap, loosen the module mounting screws first then follow

IGNITION SYSTEM565. Inspect the key, keyway, and tapered mating sur-faces of the flywheel and crankshaft. See Figure 7.16.NOTE: If the key is damaged

IGNITION SYSTEM57Spark plug removal1. Disconnect and ground the spark plug wire.2. Remove the spark plug using a 13/16” or 21mm wrench. A flexible cou

EXHAUST58The exhaust system is a frequently overlooked compo-nent of an engine. It is important to make sure the muf-fler is in good condition and fre

EXHAUST594. The spark arrestor can be:• Replaced• Cleaned by mechanical means• Solvent cleaned• Burned clean using a butane or propane torch.5. Insta

EXHAUST60Snow enginesUnlike the summer engines, the snow engines are not equipped with spark arrestors. To remove/replace the muffler:1. Remove the mu

CYLINDER HEAD61The Cylinder head of the MTD engine can be removed without removing the engine from the piece of equip-ment.To remove the cylinder head

CYLINDER HEAD629. Remove the four screws securing the valve cover using a 10mm wrench. See Figure 9.4.10. Loosen the jam nuts and fulcrum nuts that se

CYLINDER HEAD63To install a cylinder head:16. Place a new head gasket on the cylinder, allow-ing the alignment dowels to hold it in place. See Figure

INTRODUCTION1Professional Shop Manual intentThis manual is intended to provide service dealers with an introduction proven diagnostic and repair proce

CYLINDER HEAD64ValvesValves and valve parts, like springs and keepers, are not available as service parts. The valves and valve seats can be serviced

CYLINDER HEAD656. Inspect the valve seat. See Figure 9.13.• Valve seats are 45 degrees, with a 15 degree topping cut and a 75 degree narrowing cut.•

CYLINDER HEAD66Push rod bushingsThe MTD engine has bushings for the push rods that need to be replaced from time to time. An indication that the bushi

CRANKSHAFT, PISTON AND CONNECTING ROD67There are a a few different paths that can be followed when disassembling an engine. This chapter will cover th

CRANKSHAFT, PISTON AND CONNECTING ROD6813. Remove the valve tappets. See Figure 10.3.NOTE: Keep track of which tappet was originally riding on which l

CRANKSHAFT, PISTON AND CONNECTING ROD69The internal components of the MTD engine are not available as service parts. The intent of this chapter is to

CRANKSHAFT, PISTON AND CONNECTING ROD70Piston Inspection1. Clean the piston and remove all carbon from the rings and ring groves.2. Clean the cylinder

CRANKSHAFT, PISTON AND CONNECTING ROD71Connecting rod inspection1. Inspect the connecting rod for cracks or any signs of damage.2. Install the rod cap

CRANKSHAFT, PISTON AND CONNECTING ROD722. Compare the measurements to those that are listed in the chart at the end of the chapter.3. Inspect the cyli

CRANKSHAFT, PISTON AND CONNECTING ROD73Reassembly1. Clean the cylinder1a. Remove all gasket material from all mating surfaces.1b. Clean the cylinder

Chapter 1: INTRODUCTION2MTD Horizontal Engine Model Designators1 6 1 - S H ABore Dia. (mm)Starter/Alternators1=Recoil start2=Electric start3=E. start/

CRANKSHAFT, PISTON AND CONNECTING ROD744c. Slide the connecting rod and piston into the cylinder.NOTE: The arrow on the piston must point towards th

CRANKSHAFT, PISTON AND CONNECTING ROD759. Using a seal protector, slide the crankcase cover on to the crank shaft. See Figure 10.23.10. Gently rock th

CRANKSHAFT, PISTON AND CONNECTING ROD76Engine specifications chartTable 1: Specification 61 65 70Bore (new) 2.4” (61mm) 2.6” (65mm) 2.76” (70mm)Displa

CRANKSHAFT, PISTON AND CONNECTING ROD77Engine torque values chartNOTE: * - apply a small amount of releasable thread locking compound such as Loctite®

FAILURE ANALYSIS78A properly maintained engine will provide years of ser-vice. Occasionally an engine will fail. An important part of working on engin

FAILURE ANALYSIS793. Particles that enter the intake system travel at great speed and act like sand blasting media inside the engine. This causes wear

FAILURE ANALYSIS808. Because the oil absorbs the abrasive particles, the engine components that are immersed in oil will show definite signs of abrasi

FAILURE ANALYSIS81The hall mark of a lubrication failure is the pres-ence of discoloration and/or metal transfer on all friction surfaces within the e

FAILURE ANALYSIS82OverheatedThe MTD engines are air cooled engines. Because of this, cleanliness of the engine is very important to the life of the en

FAILURE ANALYSIS83Mechanical Breakage/ WearSometimes an engine fails because a part breaks. There are generally three causes of a broken part, out-sid

INTRODUCTION3MAINTENANCEThe information in this manual applies to the MTD engine. Some basic principles may apply to engines producted by other manufa