2-CYCLE GTS 120 ENGINE SERVICE MANUAL Table of Contents – Page 1 of 1 PREFACE I. GENERAL INFORMATION SAFETY INSTRUCTIONS MAINTENANCE MODEL AND SERIAL NUMBERS TWO-CYCLE ENGINE THEORY AND OPERATION CARBURETOR THEORY AND OPERATION SPECIAL TOOLS LIST II.
PREFACE This service manual was written expressly forTORO Two-Cycle Rotary Mowers. All units with the model number 47P22,47PD3,47PE4, and 47PF5 engines have been taken into consideration. effort to make this service manual a useful The Toro Company has made every tool for the service and maintenance of your TORO Rotary Mower Engine. To assure proper and effective performance, you areurged to read this manual carefully.
TABLE OF CONTENTS TOPIC PAGEE 1 GENERAL INFORMATION .................................................................... 1-1 Safety Instructions ................................................................................ 1-1 Maintenance ....................................................................................... 1-2 Model and Serial Numbers ................................... .,.................................... 1-2 Two-cycle Engine Theory and Operation ....................................
SAFETY INSTRUCTIONS Your rotary mower at the time of its manufacture, meets the blade safety requirements of the Consumer Product Safety Commissions Safety Standard for Walk Behind Power Lawn Mowers. A representative sample was testedand verified by an independent laboratory for compliance with the B71.1-1980 Specifications of the American National Standards Institute. However, improper use or maintenance by the operator or owner can still result in injury.
rocks are not thrown. 17. Before leaving the operator’s position behind the handle, stop the engine and wait for all moving parts to stop. Do not walk in front of the mower while the engine is running. Disconnect the high tension wire from the spark plug if the mower will be unattended. 18. Do not touch any part ofthe engine while it is running or shortly after it is stopped because the engine will be hot enough to cause a burn. Muffler is extremely hot.Keep children and pets away. I MAINTENANCE 19.
the exhaust ports. The third port design engine has the carburetor mounted on the side of the cylinder. The passage from the carburetor into the crankcase is called the third port. All ports within the engine areopened and closed by the piston skirt as the piston moves up and down within the cylinder. gases begin to beexpelled from the combustion chamber (Figure 1-3).
Air passing through the pilot jet from the pilotair carburetor causes atmospheric pressure to push fitting draws fuel out of the pilot jet orificefrom rawfuelfrom thefloat bowl into theairstream,where the float bowl. This fuel pre-mixes with the it breaks up into a fine spray, or becomes atomized, incoming air, then is discharged into the carandmixes withthe air stream (Figure 1-5). buretor bore where the fuel becomes atomized (Figure 1-7).
ENGINE SPECIFICATIONS ~ - - Model 47P22 Type cycle, 2 single cylinder piston ported, aircooled Rotation (viewed from output end) Counter-clockwise Displacement cc121in) cu. (7.38 Bore 58 (2.28 mm in) Stroke in) (1.81 46 mm Crankshaft (.98in) mm24.9 forged steel Rated Output 3.5 Hp @ 3600 RPM (5.28 kg-mTorque .73 ft-lb) @ 3000 RPM Compression Ratio 6: 1 Compression 8.4kps/cm2 20 psi) to 10.5 kps/cm (1 50 psi) 50:1 Gas-Oil Ratio Gasoline Unleaded Regular T Oil T O 2 cycle oil Fuel Tank Capacity 1.
SPECIAL TOOLS LIST ITEM 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 DESCRIPTION Flywheel Puller.. .................................. Starter Cup Wrench ................................ Timing Tester.. .................................... SparkTester ...................................... Continuity Light ................................... Tachometer.. .. ................................. Ohmmeter (Multimeter). ........................... . Feeler Gauges....................................
SPARK PLUG Many times an inspectionof the spark plug can determinewhethertheengine isfunctioning properly. A spark plugwhichisfunctioning normallywill show slightelectrode wear with brown or greyish tan deposits. Oil fouled and black carbon fouled plugs are caused by a rich carburetor mixture, weak spark, or improper gasoline to oil mixture. Excessively worn electrodes ora blisteredinsulator indicate spark plug overheating.
remove the muffler from the engine by removing the tworetaining nuts and the throughbolt (Figure 2-3). the loose carbon from the muffler using compressed air.Install the muffler using a new gasket and attach it with proper fasteners tightened to the correct torque. See page 1-5. DECARBONING CYLINDER HEAD If the exhaust ports andmuffler show signs ofexcessive carbon buildup, it may be necessary to de-carbonthecylinderhead.
IGNITION TIMING(DIAL INDICATOR) The ignition timing may be more accurately checked using a dial indicator. Removethe spark plug wire and spark plug and insert the dial indicator into the spark plug hole. Rotate the engine crankshaft until the dial indicator registers the piston at top dead center and “zero” the dial. Connect one lead of a timing tester to the engine frame. (A timing tester must be used. An Ohmmeter or continuity light will not indicate the position of thecontact points.
GOVERNOR The ignition coil contains two separate windings The governor linkage is factory preset to reguinside the coil casing (Figure 2-9). Use an Ohmat 3000 150 RPM. meter to check the resistance levels of each wind- latetheenginespeed Check the adjustment of the governor if the ing. Tocheck theprimary winding,disconnect the engine is suspectedof improper speed.
GOVERNOR OPERATION (Refer to Figure 2-13.) As load on the engine increases the enginespeed will start todecrease.As the engine slows downthe centrifugal force of the flyweights (1) will decrease. The governor return spring (4)will cause the governor collar (2)to move in direction (A).The governorarm (3) will also move in direction (A)causingthe throttle toopen until the centrifugal force of the flyweights are in balance with the governor return spring.
CARBURETOR The non-adjustable carburetor has a number of small orifices which control the flow of fuel and air to obtain the proper combustable mixtures. If stale or dirty fuel enters the carburetor, deposits canformcausing adverse changestothis cornbustable mixture. To clean the carburetor it must first be removed and disassembled. (See Disassembly Instructions.) Soak all metal parts in carburetor cleaner to remove deposits.
111. TROUBLESHOOTING AND TEST PROCEDURES Generally all gasoline-powered products require some form of service or repair during their plug. lifetime. The amount of time and expense involved in repairing a product can be greatly impacted by the amount of time required toinitially determine the cause of the difficulty. Therefore, it is recommended to make thesepreliminary checks before proceeding tosecondary troubleshooting procedures. PRELIMINARY TROUBLESHOOTING Ignition System 1.
3. Disconnect the wire leading to the ignition switch and connect acontinuity testerto the switch wire and engine frame(Figure3-2) with the control bar in the “STOP” position there should becontinuity through the switch. With the controlbar in the“START” position, there should be NO continuity through the switch. 4. Adjust the cable or replace the switch whichever is necessary to assure that the switch and brake assembly are functioning properly.
2. Pull the starter rope rapidly several times until the compression reading on the gauge stabilizes. 3. If thecompression readingis below 6.5 kps-cm2 (92 psi),cylinder, piston or ring damage should be suspected. A new engine should have 8.4 kps-cm2(1 20 psi) 1 0.5 kps-cm2(1 50 psi). An engine with low compression must be disassembled and inspected for damage of the internal components. (See Disassembly Instructions.
ENGINE TROUBLESHOOTING CHART The following troubleshooting chart lists the symptoms,causes and remedies of common engine malfunctions. Once the symptom beendetermined, systematically eliminate the possible causes until the actual cause is found. The possible causes have been arranged with the most easily inspected items to be checked listed first.
IV. ENGINE REMOVAL, DISASSEMBLY REPAIR INSTRUCTIONS ASSEMBLY AND iS ENGINE REMOVAL To remove the engine from the mower the air cleaner housing, recoil assembly and fuel tank must first be removed to disconnect the control cables.Remove the retaining capscrew, lockwasher,blade, blade adapter and self-propel componentsbelow the mower deck fromthe engine crankshaft. Remove the four capscrews that retain the engine to the mower chassis and remove the engine from the mower.
flywheel by hand and remove the three remaining capscrews retaining the starter cup to the flywheel. (Itmay be necessary to insert a screwdriver through the starter cup to hold the flywheel should the capscrews be extremely tight.) IMPORTANT: DO NOT DEFORM THE STARTER CUP OR STARTER ENGAGEMENT DIFFICULTY MAY RESULT. 9. Use the flywheel Duller listed in the Special Tools Section to pull the flywheel from the crankshaft. IMPORTANT:DONOT PRY ONTHEFLYWHEEL CASTING OR STRIKE THE CRANKSHAFT OR DAMAGE WILL RESULT.
the crankcase. Usea seal pick toremove the governor shaft seal. NOTE: The cylinder contains a cast iron sleeve, however, this sleeve is not replaceable. The purpose of the sleeve retainer ring is to assist the manufacturing process and hold the cast iron sleeve in place to limit engine damage should the sleeve loosen during operation.
adapter plate with the dimple facing the spark plug end. Install the four retaining capscrews and torque to the proper specification. 7. Install the ignition cam and locating pin to the flywheel end of the crankshaft. Install the condenser andpointsin position. Rotate thecrankshaft until thecam followeris on the high point of the cam. Adjustthe point gap using a feeler gauge of the appropriate size to set the air gap at .35mm (.014 in). (47PZ2engine only.) 8.
Cylinder bore The cylinder bore is checked by measuring the cylinderliner at a total ofsix places using a cylinder gauge. Two measurements, apart, must be taken at the approximate A, 6 and C elevations as shown. Readings larger than the listedspecificationsindicatean excessively worn bore and the cylinder block must be replaced. The cylinder liner is not a serviceable part of the engine.
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