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IGNITION SYSTEM

Testing

Check the ignition system in the following order:

Spark plug (connection & wire, condition).

CD Pack (air gap, connections or spark).

Flywheel (key and magnets).

Use the table above to aid in diagnosing the problem.

Spark Plug Operation

The spark plug ignites the oil-fuel mixture by producing
a spark just before the piston reaches top dead center
(TDC). A spark plug is typically constructed as shown.
(See Figure 46.)

Figure 46

3297-014

Troubleshooting

Problem

Possible Cause

Suggested Remedy

Misfiring, no firing, engine surges,
engine dies (Note: these
symptoms may also be caused by
fuel system problems)

Spark plug or lead wire loose

Tighten plug

Spark plug in poor condition

Replace plug

CD Pack air gap wrong

Adjust

CD Pack high tension lead loose

Secure with GE silicon sealant

CD Pack leads loose, dirty, or
grounding

Clean and tighten leads/replace

CD Pack defective

Replace CD Pack

Flywheel key damaged or sheared

Replace key and check keyway
(see Servicing the Flywheel in this
section)

Flywheel magnets demagnetized
or weak

Replace flywheel

Engine will not stop

Broken ground wire

Check the ground wire between the
mag and kill switch. Look for
breaks or loose connections.

A. Metal Shell
B. Center Electrode
C. Ground Electrode

D. Head Insulator
E. Copper core
F.

Leg Insulator

G. Gap

Summary of Contents for DuraForce

Page 1: ...e of Contents Page 1 of 1 PREFACE SAFETY SPECIFICATIONS SPECIAL TOOLS TROUBLESHOOTING MAINTENANCE CARBURETOR FUEL SYSTEM IGNITION SYSTEM REWIND STARTER ENGINE PIVOTING ZONE START BRAKE ELECTRIC START SYSTEM 120 VOLT ELECTRIC START SYSTEM 12 VOLT ...

Page 2: ......

Page 3: ...two versions a heading will state which engine is being discussed We have made every effort to make this information complete and correct We hope that you find this manual a valuable addition to your service shop If you have questions or comments regarding this manual please contact us at the following address The Toro Company Consumer Service Department 8111 Lyndale Ave So Minneapolis MN 55420 11...

Page 4: ...Low Compression 7 Engine Lacks Power 8 Engine Surges 8 Engine Backfires 8 Engine Overheats 9 Engine Vibrates Excessively 9 Engine Crankshaft Will Not Turn 9 Engine Produces Mechanical Knocking Sound 9 Engine Pre Ignites 10 Engine Smokes Excessively Smoke is light colored engine runs well 10 Engine Smokes Excessively Smoke is dark engine runs poorly 10 Engine Stalls 11 Spark Plug Fouled 11 MAINTENA...

Page 5: ... Engine DuraForce Engines Only 26 Piston Ported Engine R tek Engines Only 26 Presetting the Governor DuraForce Engines Only 26 Servicing the Air Filter DuraForce Engines Only 27 FUEL SYSTEM 29 Operation 29 Fuel Cap Service 29 Cleaning 29 IGNITION SYSTEM 31 Troubleshooting 31 Testing 31 Spark Plug Operation 31 Spark Plug Service 32 CD Pack Operation 32 CD Pack Air Gap Adjustment 33 CD Pack Removal ...

Page 6: ...ngines 40 Service Tips 41 Disassembly 41 Inspection and Repair 42 Reed Valve Service DuraForce Engines Only 43 Reassembly 44 PIVOTING ZONE START BRAKE 47 Introduction 47 Operation 47 Disassembly 48 Assembly 49 ELECTRIC START SYSTEM 120 VOLT 51 Troubleshooting 51 Introduction 51 Starter Removal 51 Starter Disassembly 52 Starter Assembly 52 Starter Installation 52 Reinstalling External Components 45...

Page 7: ...ing 53 Introduction 53 Starter Removal 53 Starter Testing 54 Starter Disassembly 54 Starter Assembly 55 Starter Installation 55 Alternator Introduction 56 Alternator Output Testing 57 Alternator Air Gap Adjustment 57 Alternator Resistance Check 57 Cup Assembly Test 57 ...

Page 8: ...ning or has the potential to start Avoid burns Do not touch the engine while it is running or shortly after it has been running Avoid Falls Do not operate the powered product on slippery surfaces or if footing is questionable Avoid fires Wipe up any spilled fuel or oil immediately Avoid asphyxiation Never operate an engine in a confined area without proper ventilation Avoid fires and explosions Us...

Page 9: ... Toro 2 cycle oil or NMMA TCW3 Fuel tank capacity Ignition type CD Pack air gap Spark plug air gap Start system Rope rewind or 12 VDC Rope rewind or 120 VAC Governor Governed Engine Speed 2900 300 rpm 4HP runs at 3700 300 CCR 2400 3700 5HP runs at 3800 300 rpm CCR 2450 2500 3800 rpm CCR 3600 3900 rpm CCR 3650 4000 rpm Snow Commander 4000 rpm All snow engines are 300 rpm Idle Speed 2200 2800 rpm N ...

Page 10: ... 2 3 4 Nm Screw CD Ignition Pack 90 110 in lbs 10 12 Nm 90 110 in lbs 10 12 Nm Screw Cylinder to Crankcase 55 90 in lbs 6 2 10 0 Nm 55 90 in lbs 6 2 10 0 Nm Screws Engine Mounting 170 220 in lbs 19 25 Nm 170 220 in lbs 19 25 Nm Screw Float Bowl 10 13 in lbs 1 1 1 5 Nm 10 13 in lbs 1 1 1 5 Nm Screw Muffler 611228 55 90 in lbs 6 2 10 0 Nm 55 90 in lbs 6 2 10 0 Nm Screw Muffler Cover 55 90 in lbs 6 2...

Page 11: ... 2 11 Nm Size US Metric 10 24 20 30 in lbs 5 1 6 21 Nm 1 4 20 55 90 in lbs 6 2 10 0 Nm 5 16 18 140 200 in lbs 16 22 Nm Item DuraForce R tek Type Lawn Boy float type dual circuit with primer and choke Body Material Minlon Seat material Brass with Viton tipped needle Both are replaceable Inlet Needle Pop Off Pressure 5 psi 7 kg cm2 Wet Main Jet 77 5 73 8 Main Nozzle Brass Pilot Jet 37 5 42 5 High Al...

Page 12: ...gap between flywheel and coil Piston Ring Compressor OTC TOR 4089 Compresses piston rings to allow installation into the cylinder Wrist Pin Knockout Tool Toro 602884 Used to drive wrist pin out of piston OTC Tool Equipment Division SPX Corporation Industrial Park 2013 4th Street NW Owatonna MN 55060 Telephone 800 533 0492 Fax 507 455 7011 ...

Page 13: ...Spark table Insufficient momentum Check for loose blade mower only Incorrect ignition timing Check for sheared flywheel key Low compression See Engine Has Low Compression table Engine flooded with fuel See Engine Flooded With Fuel table Reed valves not closed Replace reed valves DuraForce only Reed valves stuck closed Free up and run engine to clean DuraForce only Primer or choke not operating Fix...

Page 14: ...ets weak Replace flywheel Possible Causes Remedies Overuse of choke position Take throttle off choke Throttle cable misadjusted Adjust throttle cable if present Air cleaner plugged Wash and re oil air cleaner element DuraForce only Fouled spark plug Replace spark plug Carburetor inlet needle stuck open or leaking Clean carburetor replace failed parts and pressure test Carburetor Air Vent Clean Air...

Page 15: ... compression See Engine Has Low Compression table Possible Causes Remedies Fouled idle circuit Clean idle circuit Air leak Check sealing surfaces oil seals gaskets and port plugs Restricted fuel flow Check filters and fuel line Engine RPM low Adjust to proper specification Note A slight surge at no load is normal Governor link misadjusted R tek Adjust Air vane sticking Clean or replace Possible Ca...

Page 16: ...ighten engine mounting screws engine to plate plate to mower housing Bent crankshaft Replace crankshaft Flywheel out of balance damaged Replace flywheel Possible Causes Remedies Engine brake incorrectly engaged Disengage brake and inspect and repair as necessary mower only Blade jammed in housing Inspect and repair or replace mower only Piston seized in its cylinder Inspect and repair or replace S...

Page 17: ...xcessive alcohol in fuel Replace with fresh unleaded fuel having no more than 10 ethanol Sheared flywheel key Inspect and repair Possible Causes Remedies Slight oil accumulation in crankcase None normal on start up Air cleaner element clogged Clean and re oil or replace air cleaner element mower only Fuel oil mixture too rich Drain fuel tank and fill with fuel of correct mixture Choke is in On pos...

Page 18: ...per lubrication Tear down and inspect for damage Possible Causes Remedies Incorrect spark plug Use correct spark plug Carburetor running too rich Clean rebuild carburetor Clogged air cleaner element Clean and re oil element or replace mower only Overuse of choke position Move control off choke position and check throttle cable adjustment Weak ignition system Replace CD ignition pack Worn rings and...

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Page 20: ...very 50 hours more frequently if operating conditions are dusty Blade Blade Brake Mower only Sharpen or replace maintain more frequently if edge is dulled quickly in rough or sandy conditions Check stopping time every 50 hours or at start of each mowing season Blade must stop within 3 seconds of releasing bail If not repair or replace Lubrication Self propelled mowers only Grease rear height adjus...

Page 21: ...006 3 Apply one tablespoon SAE 30 or similar oil to the air filter see Figure 3 Lightly squeeze filter until oil is distributed evenly throughout the filter Blot lightly with paper towel to remove excess oil Replace filter with cleanest side facing carburetor Note Be sure filter is properly seated in air box and is not puckered allowing direct passage of air and dirt to carburetor Figure 3 3297 00...

Page 22: ...cover and the exhaust pipe under the cover See Figure 7 Figure 7 1657 010 Figure 8 1657 001 3 With the cover and exhaust pipe removed you can see into the passage leading to the exhaust port of the engine A and passage to the muffler B If the exhaust requires cleaning remove the engine and separate the engine and base for access to the exhaust ports If the muffler requires cleaning it can be remov...

Page 23: ...11 0893 035 3 Install the muffler and torque the bolts per specifications Reassembling Exhaust System Mower Only 1 Install the exhaust pipe into the engine base see Figure 12 Figure 12 16547 006 2 The cover on the exhaust portion of the engine base uses a high temperature silicone to seal the joint Apply a coat of Loctite 598 or equivalent to the sealing surfaces before assembly Torque the four sc...

Page 24: ...e in the crankcase The carburetor throat is formed into a venturi large at each end but with a smaller center passage When air rushes through the venturi air pressure at the center of the passage is lowered By inserting a tube from the carburetor float bowl into the venturi see Figure 14 the lower air pressure at the venturi causes the normal air pressure in the bowl to push fuel up the tube Figur...

Page 25: ... pinched Inspect and correct problem Dirt in primer vent Clean and or replace as necessary Choke not opening fully Adjust choke or throttle choke cable Engine Runs Lean Possible Causes Remedies Carburetor bolts not tight Tighten bolts to specifications Crankcase gaskets or seals leaking Replace or reseal Main jet partially clogged Clean jet Pilot jet or circuit clogged Clean pilot jet and passages...

Page 26: ...he exterior of the carburetor before removal from the machine This reduces the chance that dirt can get into the carburetor and will extend the life of the solvent in your cleaning tank 2 Remove fuel line and drain remove the fuel tank On snowthrowers it will be necessary to remove the lower shroud to access the carburetor and fuel line 3 Open and remove air cleaner cover and air filter element mo...

Page 27: ...roud to access the carburetor and fuel line 3 The carburetor is attached to the intake pipe by two screws which are screwed into two captured nuts The nuts are held in their pockets by a rubber band during the manufacturing process If the rubber band is no longer in place smear some general purpose grease on the nuts to prevent them from falling out of the pockets Remove the two screws and discard...

Page 28: ...gure 21 Figure 21 0893 005 3 Turn the carburetor over Remove the four bowl retaining screws the bowl gasket and the bowl See Figure 22 Discard the bowl gasket Figure 22 0893 002 4 The pilot jet is located under the decal on the side of the carburetor Remove the decal and the pilot jet Note The threads have Loctite on them See Figure 23 Figure 23 0893 30 5 Remove the fuel filter from the fuel nozzl...

Page 29: ... 28 Note There are two white nylon plugs in each carburetor Do not attempt to remove them or the carburetor will be damaged Figure 28 0893 037 Cleaning and Inspection 1 With the carburetor completely disassembled thoroughly clean all parts in a parts cleaning solution Do not soak the carburetor Leave it in the solvent only long enough to clean it Inspect for wear or deterioration Use a spray can o...

Page 30: ... Figure 30 0893 030 4 Apply one drop of Loctite 242 or equivalent to the seat threads and install a new brass inlet fuel valve seat see Figure 31 Figure 31 0893 041 5 Install a new inlet valve needle and clip on the float 6 Install the float assembly with a new float hinge pin in the bottom of the carburetor Ensure that the hinge pin is positioned properly to keep the float level The float should ...

Page 31: ...not hold wet the needle and seat and repeat the test Figure 33 0893 026 9 Install the fuel filter over the fuel nozzle Pressure check before proceeding see Figure 34 Figure 34 0893 22 10 Install a new fuel bowl gasket and the fuel bowl with the four bowl retaining screws see Figure 35 Figure 35 0893 002 11 Hook the governor spring into the bottom of the governor collar DuraForce engines See Figure...

Page 32: ...e throttle plate is in the full open position The cable is adjusted at the cable clamp on top of the air filter box R tek engines Connect the governor spring to the throttle plate and the tab on the block Connect the governor rod adjusting loop A up to the air vane and connect the choke cable Assure the throttle is in the full open position See Figure 38 and Figure 40 Figure 38 724 004 4 Install t...

Page 33: ... engine RPMs or counterclockwise to decrease spring tension and RPMs See Figure 39 Preset the governor collar 3 or 4 clicks clockwise 2 Use a tachometer to check engine speed 2900 300 RPM for DuraForce engines on mowers For R tek piston ported engines refer to the specification pages Should the governor link A be bent or replaced adjustment will be necessary See Figure 41 Figure 41 0893 039 A good...

Page 34: ...3 Figure 43 0893 017 2 Clean and re oil the air filter element according to the procedure in Maintenance section CAUTION Do not operate the engine without a filter element or with a dry element engine life will be shortened Note Snowthrower engines do not have an air filter for two reasons a The snow prevents dirt from getting into the air b In colder weather the snow will blow around Fine particl...

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Page 36: ... into the tank from an opening in the cap to allow gravity to feed fuel to the carburetor If an individual part of the cap fails the entire assembly must be replaced Figure 44 0720 022 Fuel Cap Service 1 The fuel cap may not be disassembled however the vent opening on the cap and inner sealing disc should be kept free of debris 2 The venting ability of the cap may be tested by filling the cap with...

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Page 38: ...ne dies Note these symptoms may also be caused by fuel system problems Spark plug or lead wire loose Tighten plug Spark plug in poor condition Replace plug CD Pack air gap wrong Adjust CD Pack high tension lead loose Secure with GE silicon sealant CD Pack leads loose dirty or grounding Clean and tighten leads replace CD Pack defective Replace CD Pack Flywheel key damaged or sheared Replace key and...

Page 39: ...k an AC voltage is induced into the charge coil This AC voltage is converted by a rectifier into a DC signal which is then stored in a capacitor See Figure 48 Figure 48 3297 016 When the SCR is triggered or fires up to 200 volts DC stored in the capacitor travels to the spark coil Here it is stepped up to as much as 25 000 volts and is discharged across the electrodes of the spark plug See Figure ...

Page 40: ...r Gap Adjustment 1 Rotate the flywheel until the magnets are directly adjacent to the CD Pack as shown See Figure 52 Figure 52 lbv0040a 2 Adjust gap by loosening screws inserting Lawn Boy gauge P N 604659 or a piece of 010 25 mm shim stock and tightening screws Remove the shim stock or gauge CD Pack Removal Installation 1 Disconnect leads and remove mounting screws 2 Replace CD Pack and set gap as...

Page 41: ...with the torque of the bolt or nut actually holds the parts together The surfaces of both tapers must be good to obtain a good friction fit The key is designed as a light duty part so that if the engine stops rapidly due to blade impact the key will shear If the key were too hard and the impact occurred the more expensive flywheel could crack Flywheel Removal 1 Remove shroud and fuel hoses 2 Remov...

Page 42: ... See Figure 57 Figure 57 0893 013 Flywheel Installation 1 Make sure flywheel taper crankshaft taper and keyway is absolutely clean and dry 2 Make sure key is installed correctly see Figure 58 3 Locate keyway cutout in flywheel over key and shaft Figure 58 3297 020 4 Torque flywheel nut to specifications see Figure 59 Figure 59 0893 025 ...

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Page 44: ... the shroud to the base Also there are 2 studs B on the cylinder head that are used to attach the shroud Remove the nuts and washers from the studs The shroud can then be rotated towards the cylinder head until there is enough clearance to slide the shroud off the studs See Figure 60 Figure 60 720 002 3 Drill out the rivets connecting the recoil and the shroud Note the orientation of the starter 4...

Page 45: ...is installed Figure 62 lbv0043d bmp 3 Reassemble the starter and shroud with the four screws and nuts Remember the orientation of the rope outlet 4 The shroud must be assembled by slipping the shroud over the two studs on the cylinder head then rotating the shroud down until the holes on the engine block and shroud align Install the nuts on the studs and two screws on the side opposite the head No...

Page 46: ...tation and the piston begins its travel toward the spark plug As it moves the piston seals off the transfer port first then the exhaust port When both ports are sealed the remaining travel compresses the air fuel mixture to prepare it for ignition The travel of piston towards the spark plug is called the compression stroke See Figure 65 The movement of the piston towards the spark plug also has an...

Page 47: ...3297 002 When the piston opens the exhaust port high pressure exhaust gases exit the exhaust port See Figure 68 Further movement of the piston towards the crankcase uncovers the transfer port which allows a fresh charge of oil fuel mixture to enter the combustion chamber As the exhaust gases continue to exit the exhaust port the engine is readied for another cycle See Figure 69 Figure 68 3297 003 ...

Page 48: ...inspected and cleaned as necessary see page 15 5 Carburetor Gaskets Carburetor gaskets on either side of the carburetor shield may be leaking or damaged causing air leaks into the engine may cause power fluctuations Ensure that air cleaner carburetor mounting screws are properly tightened see Specifications Disassembly Removal of the shroud recoil starter flywheel ignition coil and carburetor are ...

Page 49: ...s for sticking Remove and check rings for wear or damage replace rings if questionable Clean any carbon buildup from the ring grooves before installing new rings It is best to use a piece of hardwood to scrape carbon loose Should you use a metal tool you might damage the piston 3 Check all parts for wear or damage and replace if questionable 4 Clean crankcase surfaces with Gel Seal and Gasket Remo...

Page 50: ...tion Without the necessary lubrication friction increases and overheats the piston Often in an engine that failed due to improper lubrication the piston is discolored the rings may be stuck yet the lower rod and crankshaft bearings might appear usable As the piston is the source of the friction and heat the bearings further from the heat source may not appear damaged However we would not recommend...

Page 51: ... pins 3 Assemble ball bearings to crankshaft and install crankshaft 4 Note One side of the paper is sticky remove paper carefully while installing needle bearings There should be 32 needle bearings on the lower connecting rod When reinstalling original needle bearings use a little 2 bearing grease to stick the needles to the rod 5 Install rod cap A Ensure that mating marks are aligned Clean old sc...

Page 52: ...ews to specifications tightening only 20 in lbs 2 26 Nm increments at a time while tightening modified X pattern See Figure 83 Figure 83 0891 005 Reinstalling External Components 10 Reattach the flywheel brake system 11 Clean the crankshaft and flywheel hub with alcohol and install flywheel 12 Install carburetor and governor assembly 13 Install starter and shroud assembly and starter handle 14 Rec...

Page 53: ...d after assembly These seals should be recessed between 040 and 060 1 016 1 524mm Check the depth in about 3 places to ensure Figure 85 0893 016 A Separate the crankcase from the cyclinder to replace the seals Slide the seals off the crankshaft and clean the case mating surfaces as previously indicated Clean the block where the seal goes and the outside of the crankcase installed after the six cap...

Page 54: ... Operation The pivoting style zone brake system has two main functions The first function of the system is to stop the production of spark and the second is to stop the engine and the blade Stopping spark production is controlled by a switch The switch is closed when the blade control bail is in the at rest vertical position See Figure 86 Lowering the bail to the main mower handle opens the switch...

Page 55: ...he brake pad and the brake plate are replaceable only as an assembly 2 To reduce the pressure of the spring between brake mounting plate 10 and brake plate 8 squeeze tabs of brake cable that hold it in place at the brake mounting plate Push cable through the hole in brake mounting plate 3 Slide cable out through horizontal slot in brake mounting plate Also slide the ball end of the cable up throug...

Page 56: ...ble into the narrow slot on the brake mounting plate and then push the cable into the hole making sure the tabs lock into the bracket 4 One end of the compression spring has a hook shape to it that end hooks over an indentation in the brake plate Squeeze the compression spring A and slip it over the cable between the brake mounting plate and brake plate See Figure 90 Figure 90 0893 051a 5 Insert t...

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Page 58: ...holding the wire clip and the two bolts which mount the starter to the engine See Figure 93 Figure 93 1657 017 Starter Motor Fails to Turn Possible Cause Correction Power not reaching product Plug another appliance into extension cord to ensure cord is OK Starter switch malfunction Check switch using a volt ohmmeter set for resistance Ensure that there is continuity when the switch is depressed En...

Page 59: ...t 3 Remove the two housing bolts and separate the ends from the body Pay close attention as things come apart easily when disassembling 4 The serviceable items are shown See Figure 94 Figure 94 1657 022 5 The starter switch is also serviceable See Figure 95 Note The wires can be removed by inserting a small diameter drill bit into the holes to release the jaws Figure 95 1657 021 Starter Assembly A...

Page 60: ...he starter pin with a 1 4 Allen wrench See Figure 96 It may be necessary to remove the carburetor bolts and lower the carburetor to gain access the needed clearance for the Allen wrench Figure 96 1657 005 Starter Motor Fail to Turn Possible Cause Correction Starter motor has failed Check by disconnecting the spark plug wire and starter wiring connector Apply 12 volts directly to the starter motor ...

Page 61: ...n 10 ohms If high resistance or open circuit infinite resistance is shown replace the starter motor Starter Disassembly 1 Slide the pinion clutch assembly A off the pinion shaft Remove the retaining ring from the pinion clutch assembly and disassemble completely Inspect all parts for wear or damage and replace as needed See Figure 98 Figure 98 1657 020 2 Remove the two screws and drag spring stud ...

Page 62: ...sembly and secure with two screws and drag spring stud Make sure you replace the drag spring stud in its original position Torque screws and stud to 20 in lbs 5 Reassemble pinion clutch assembly Apply a small amount of Lawn Boy AX grease to the pin Slide the assembly on to the pin with the drag spring A over the stud See Figure 102 Figure 102 1657 020 Starter Installation 1 Install the starter lea...

Page 63: ...arge rate of this alternator is 500 milliamps Due to the low charge rate it is important to use the 120 volt charger to fully charge the battery before initial use and at the start of each season Frequent starts or hard starting may require using the 120 volt charger to recharge the battery See Figure 103 Figure 103 12v tif Note Fuse 5 amp 2 blade automotive ...

Page 64: ... gap is incorrect loosen the alternator mounting bolts slightly allowing the flywheel magnets to pull alternator against the gauge Tighten the bolts to 75 in lbs and recheck the air gap See Figure 104 Figure 104 6 tif Alternator Resistance Check 1 Disconnect the electronic cup assembly from the wiring harness Connect one ohmmeter RX 1 scale lead to the green wire of the wiring harness and the othe...

Page 65: ...nce Reverse leads and measure resistance again The specification is to have different resistance between the two measurements high one way and low the opposite way If specification is not met replace the cup assembly See Figure 106 Figure 106 0891 003 ...

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