Alsoaddedunderthedeck operator releases thebail. The engine continues is a crankshaftsupportlocated to run with this system. Silverplated bearing liner at the big end of the connecting rod. Ib safety standards for rotary-type Displacement is increased mowers. We proudly display from 6. Rotary mowers are generally designed with On the rotary mower, heightof cut is changed four wheels to support a housing on top of by changing the wheelheight. The cutting which is mounted the engine,andwith the blade is usually attached directly to the en- cuttingblade mounted horizontallyinside gineshaft,and is generallymade of tem- and beneath the housing.
Length of the cutting blade is determined by the size of Theblade is designed to "lift" the grass as the mower housing. This insures even cutting. Rotary mowers are capable of cutting level, The housing covers the blade, channeling thecleanlawns, as well as roughlawns. They flow of g r a s s out a dischargechute. Ridding are limitedintheircuttingabilityinheight thehousing of cut g r a s s e s is a necessity, of grass or weeds ,only by theamount of in ordereliminate to power loss.
There are four main Differences in the operation of 4-cycle and 2-cycle engines: POWER - Number of power strokes per crankshaft revolution. Piston movement creates vacuum in crankcase. Fuel Entry Reed valve opens. Fuel air vapor enters crankcase. As piston reaches top of cylinder, fuel vapor in cylinder is compressed. Explosion forces piston down, delivering power. Downward movement of piston creates pressure in crankcase. Intake ports openas piston moves by - Crank- case pressure forces fuel vapor to rush into cylinder.
Incoming fuel vapor clearscylinder of all burnedgases. Valve Closed. Fuel vapor is being compressed Fuel enters compression chamber for igniting. Burned vapors are forced out of cylinder. The 4-cycle engine requires a separate sys- The 2-cycle engine is always lubricatedas long as tem of lubrication, with anoilsump that there is a fuel mixture in the fuel tank.
No atten- must be kept full and operated on a fairly tion to oil level is required, as the oil is pre-mixed level surface to prevent lack of lubrication with the fuel. The engine is kept lubricated re- to internal moving parts. The 4-cycle sys- gardless of angle of operation. The oil, suspended temincludes an oilreservoir,slinger or in the fuel vapor, adheres to the surfaces of all oil pump which are ineffective if the mower the moving parts, keeping them continually engine is run with a low oil supply or tilted coated witha film of oil.
These can be repaired All are additional parts required for 4-cycle o r replaced with the simplest of working engines. These create morefriction,more tools. No valves to grind, cam shafts, push wear, and requiremoreequipment,extra rods,timinggears,valvesprings,etc. This manual applies directly to Lawn-Boy products produced between and It is also used for servicing the F Series engine used on select Lawn-Boy walk mowers through This manual, form , is several hundred pages long.
For ease of use in electronic form, this manual has been broken down into numerous smaller files. Please ensure the file you are viewing is the correct one for the machine being serviced. Did he say "hello," then rush you right into the operating room and remove your appendix?
If he did, he would probably soon lose most of h i s patients, in one way o r another. What he probably did first was to set youdown and ask you some questions.
Thenheprobably made a few tests, such as temperature, blood pressure, etc. With the re- sults, he could make more specific tests and arrive at an accuratediagnosisbeforetreating you.
Because of your doctor's training and careful diagnosis, you haveconfidence in him. You, as a service repairman, can instill confidence in your customers by a careful diagnosis of their mower troubles.
Diagnosis is a talent, a talent which must be learned and continually practiced. A service repairman must also follow a set procedure in trouble diagnosis to make fast and accurate repairs. Fill out a brief report with the-customers help. Put this informa- tion on the repair ticket which will be attached to the mower.
Un- less the failure is obvious, this may help the mechanic later on, es- pecially if work is delayed for several days. Have thecustomer look overthe mower with you. Note obvioH damage, removal or alteration of safety equipment such as trailing shield, toeguard,interlockcable etc. This may protect you if any questions arise later as to the responsibility for damage. Was it used in a small or large yard, at home only o r often lent out? Was it used on level, clean lawns, rough ground, vacant lots, heavy weeds, etc?
Findout what kind of gasolineandoil is used. Pull the engine through with starter rope, and if it binds o r is dry internally indi- cating lack of oil show the customer. Normally,diagnosis takes very little time in the beginning, and will probably save a great deal of time in eliminating unnecessary repair work.
Be sure there is clean fuel in tank. Be sure gas cap vent and fuel shut-off valve are open. Feel for compression as you pullenginethrough. If engine spins very easily, it has little if any compression. With little compression, there will be little o r no power.
If engine resists pull of starter rope, it has compres- sion. If you spin an engine with good compression fast enough, you can hear the carburetor sucking air--and kick- back noise. While checking for compression, also listen for any scraping or squeaking internal noises. These noises indicate piston and cylinder scoring. If you hear such noises, do not t r y to start the engine, but turn to Section 8, Engine Repair Procedure,. Take out the spark plug and examine it. Be sure that theelectrodesareclean and the gap is.
Check theporcelain, If it is cracked,the plug won't fire. If the end of the plug i s wet, at least youknow fuel is gettingthrough.
As a further check toseethat fuel is gettingthrough,placeyourthumboverthe spark plug hole, and pullthe starter cord several times. Your thumb should be wet with fuel, b. Check spark plugusing specialtoolpart no. The spark should be hot blue and snapping. A weak spark is orange, and makes little, if any, noise. It only takes a few minutes,andthese few minutes could save you hours. If the new plug won't fire, remove the plug from the lead wire and place a bolt in the rub- ber hood, 'making contact with the spring terminal.
A good spark should jump the gap. If you don't get a spark at this point then you have ignition problems. Refer to Section 6 for detailed service information. If you have a spark at the plug even though a weak spark , check to see that the fuel mixture is getting into the combusion chamber. Remove spark plug from cylinder. If fuel mixture is entering cylinder your finger will be wet.
If fuel is not entering cylin- der refer to Section 4 for complete carburetor repair. Always check fuel tank - make sure it is clean and contains no water. Air filter element must be clean. Check for dirt or obstructions in carburetor throat. D Series - Turn carburetor adjusting knob counterclockwise two turns from seat to make sure needle is open. This restriction, results from a build-up of carbondeposits. Therefore, the muffler Tocleanexhaustports,tip mower on its plate should be removed every 50 hours of side and secureinthis position.
Remove operation o r at the end of the mowing sea- nuts securing muffler cover to muffler plate son and the exhaust ports checked for carbon and remove muffler cover. On some models accumulation. This routine maintenance the blade, blade stiffener, and adapter plate check is not only of vitalimportanceto must be removed prior to removing muffler eliminate loss of engine power, but to elimi- plate.
Pull starter rope slowly until piston covers theexhaustports. Place mower in upright posi- NOTE tion and pull starter rope several times to blow out carbon. If it wasnecessary to re- build-up. Most oilis not made for burning move blade, torque blade nut to 50 ft.
Replace tion of carbon. Upper armatureplate sealon. Thisprovidesmorepositiveseal- ing to prevent oil leaking past and foul- ing breaker point. The results are the sameas leaky seals.
Loose screws or bolts can alsopermit air to enter or leave, impairing the com- pression and vacuum cycle. Majorcastings - Check forporosityin the carburetor, crankcase, cylinder, and magneto plate. Porosityresultsfrom a defect in the casting process, and is indi- cated by tiny a i r holes i n thecasting.
This condition also results in air leaks. In some cases, the use of a penetrating ink will reveal hidden holes. A poor seal results in air and oil leakage, impairing the com- pression and vacuum cycle. Referto Sec- tion 8 for correct installation of crankcase halves. Check 4 intakeplugs forpossible leaks. Use special tool part no. Check f o r worn o r damaged upper and lower main seals.
Worn seals may develop leaks, which permit air to enter or leave crank- case, impairing the compression and vacuum cycle. Check power take-off shaft seal for damage or wear.
A worn or damaged sealresults in oil leakage and lower crankcase pressures. Approximately every 50 hours and at theclose of the mowing season check for excessive carbon accumu- lationinexhaust ports and muffler baffle. This routinemaintenancecheck is not only of vital importance to eliminate loss of en- ginepower,but toeliminateparticles of carbonfromenteringthecylinder,causing piston scoring.
Most oil is not made for burning and there- fore,resultsin heavy accumulation of carbon. To cleanmufflerbaffleandexhaustports, tip moweron its side. The hub is taperedto fit thetaper of thecrankshaft. Tap the hub with a fiber hammer to loosen it from the crankshaft. Remove three bolts securing crankshaft support and muffler to mufflerplate. Remove crankshaftsupport and muffler baffle. Reinstall adapter hub, bladestiffener washer on 21" models ,blade and blade nut.
Torque blade nut to 50 ft. Replace spark plug and reconnect high-tension lead. Pull starter handle slowly until piston covers the exhaust ports.
Place mowerin operating po- sition and pull starter handle several times to blow out carbon deposits. Reinstall mufflerandcrankshaftsupporttomower. Use special tool partno. Gasolinein a liquid f o r m i s not explosive.
The crankshaft rotates when the starter rope is pulled. The rotatingcrankshaftmoves the piston up and down in the cyl- inder. Thevacuum created by move- ment of the piston upward in the cylinderopens a reed valve - then air rushes through the throat of the carburetor.
The carburetor throat is a Venturi. When air rushes through this tube, the air pressure at the center is less. By inserting a tube from the carburetor float bowl into this AIR PRESSURE center area, the dif- ference in air pres- sure will forcefuel up through this tube, where it is picked up by,andmixedwith, the air.
A s fuel and air mixture enters the crankcase through the reed valves, it is near a gaseous state. Theengine, when cold, will not vaporizethemixturecompletely. As theengine warms up, the mixture is heated in the crankcase and becomes a consistently even gas. Start yourinspection with the fuelusedinthe2-cycle engine. Make sure yourcustomer knows the why and howof fuel mix preparation. The supply can, from which fuel is poured into the enginetank,shouldhave a water and dirt retardomg screen.
Later D Series Deluxemodels a r e equipped with aplastic gas tank assembly eliminating condensation, rust and a r e not affected by fuel mixture. Duringstorage,the tank should be empty, and the mower stored in an area not subject to extreme temperature change. Tank caps have a plainvent hole. A closed - vent will create a vacuum in the tank a s fuel is used the engine will run a few minutes and stop.
In a few minutes the vacuum will decrease and the engine can be started again, but it will stop again in a few minutes. The vent hole can become clogged with dirt. This can be checked easily by removing the fuelhose, opening the valve and observing for fuel flow through the valve. Replace the valve and screen assembly if gummed up, rusted, or if packing is damaged. NOTE Shut-off valve should be open and packing nut loose before screw- ing assembly into tank. Secure assembly to tank, then close valve and tighten packing nut.
Wing should turn easily, but snugly. As filter becomes saturated, incoming air picks up more fuel, causing greater flooding. A puckered filter will allow air and dirt to bypass filter. Make certain that filter covers cup area. If oiled, properly,filter is very efficient. First wash out with hot, soapy water. Wring out and dry completely, then apply 10 to 15 drops of oil.
Squeeze several times to distribute oil. Later D Seriesmodels have a plastic air cleaner. To remove grasp the cover lip and pull back o r fold down as required. A thorough visualinspec- The float valve consists of a needle and seat tion will determinethefuelsystem assembly, activated with a float in the float used on the engine. Theneedle is steel with rubbertip andthe seat brass, materials which will not readilyadheretogether.
Theneedle rests on the float arm, held in place by a spring clip on later models. Operation is automatic. When the float bowl is empty,thefloat rests on the bottom of the bowl. As fuel enters bowl of carburetor, the float rises, moving needle into seat and shutting off fuel.
As the engine usesfuel, the float drops slightly, allowing more fuel toenter bowl, maintaining a constantfuel level in bowl. The needle and seat must be replaced as an assembly. The cork float is coated with an epoxy sealer. If the solventremovesthe epoxy, thefloat will absorb gasoline and its floating characteristics will change.
Then open needle two turns. Start engine. If engine beginstodie, open carburetoradjusting knob by turningcounterclockwise. If engine runs roughly, close knob by turning clockwise until engine smooths out. Let engine run for about 5 minutes to warm up.
Carburetors on earlier "D" modelen- On later "D" modelengines the low gines also contain a slow speed adjustment. This jet is pressed turn open. Invert car- buretor. To adjust; bend metal a r m with needle nose pliers.
DO NOT attempt to bend by applying pressure to cork float. Carburetorservicingconsists of inspection,clean- ing, adjustment, and replacement of faultyparts. Toremovecarburetorfromengine,carburetor and reedplatemustberemoved as an assembly,. Carburetor service assemblies include 2 thread forming screws. The reed plate mounting flange on the carburetor is drilled but not tapped.
These screws form a very tight fit eliminating the possibil- ity of screws vibrating loose during engine operation. A solvent will remove the varnish from the float. Inoperative floats should be replaced. Inspect valve needlesfor grooves or other defects. If grooved or otherwise defective, replace. Use a magnifying glass in the inspection.
Tiny scratches or worn surfaces affect the operation. Be careful in handling reeds, so as not to distort them. Bent or otherwise damaged reeds cannot be repaired. Check the reed plate for warpage. Maximum clearance allowed between reed tip and reed plate is.
If clearanceexceeds this, reeds must be replaced. Prior to installing nozzle filter clean car- buretor, high speednozzle,fuel tank, fuel shut-off valve and filter assembly. DO NOT slideneopreneringover fuel passage hole. A burr on the throttle shaft arm which 2. Replace drag.
Thiscan contribute to surging. Repair - clean off burr, check governor rod for wear. Improper adjustment. If not read- ily available, use a good grade of two cycleoil from a reputable oil company. Mix thoroughly. DO NOT mix fuel directly in mower fuel tank. M i x one full can with 2 gallons U. Follow instructions on can. NOTE Fuel tanks must be vented to prevent vac- Some later model D engines are uum forming and stopping flow of fuel.
Tank equipped with the D series fuel caps will have a vent hole. A closedvent system. Athorough visualinspec- will create a vacuum in the tank as fuel is tion will determine the fuelsystem - used andeventuallycausetheengineto used on the engine.
Thecarburetorused on Solid State C. No fuel ad- justments are necessary,toregulatefuel intake. Asingle,meteredjetallows the correct amount of fuel to mix with the in- coming air which is regulated by a single adjustingneedle that is explained on page of this section. Adjustmentmustbe U.
The fuel tank screen assembly or the shut- off valvecanbecome clogged. Replace the fuel shut-off assembly if damaged. If engine is flooded, fuel can drain back into filter. A s filterbecomessaturated, in- coming air picks up morefuel,causing greater flooding. A puckered filter will allow air and dirt tobypass filter.
If oiled properly, filter is veryefficient. First NOTE wash out with fuel, then apply 10 to 15 drops of oil. Squeeze severaltimestodistributeReinstall filter inthesameposition oil. Install air filter case correctly. Hinge on To removegraspthecover,loosensnap andbottom. If installedupside down the fold cover down. Examine the primersystem. Instead of into the float bowl chamber which forces lifting fuel up in the carburetor throat as fuel ininto the carburetor venturi.
The carburetor is completely automatic. There are no adjustmentsto be madeto 6. There is anatmospheric R. Observe engine operation. All D series andmodular carburetors 7. After carburetor adjustment is com- require a finaladjustment of the altitude pleted,shut off engine. It should start service. Start engineandallow to run for 3 to 5 minutes to warm up. NOTE 4. Turnaltitudeneedleclockwiseuntilen- gine starts to "hunt," ''surge" or slow The governor will control the amount down. The pur- pose of the atmospheric pressuread- 5.
Slowly turn altitude needle counterclock- justingneedle is tomix the right wise until engine is runningsmoothly. In the closed position no air is en- tering the carburetor ventpassage. Therefore, the float bowl pressure has been eliminated and the fuel supply tothe carburetorventuri is cut off. Should be glossy because of epoxy sealer. If dull in appear- ance, o r portions of epoxy has chipped away - replace. Do not cleanfloat with any type of Operation is automatic. When float bowl is solvent or carburetor cleaner.
Clean empty,float rests on bottom of bowl, As with standard fuel mix. As engine uses fuel, float drops assembly,activated by a floatinthe car- slightly, allowing more fuel to enter bowl, buretor bowl. The steel needle is rubber maintaining a constantfuellevelin bowl. This combina- tioneliminatespossiblesticking and pro- Needle and seat must be replaced as an as- vides a perfect seal.
Theneedle rests on sembly. They are matchedtoform a per- float arm, held inplace by a spring clip. NOTE: Check dump valve and gasket for distortion o r damage.
To adjust; bend float arm with long nosepliers. DO NOT bend by applying pressure to cork float. Bend arm only by grasping with pliers. Later production models include bronze shaft, disc 1. Remove reed plate assembly. Usingneedlenose pliersgraspthrottle disc and remove disc from throttle shaft. Inspect disc for wear or burrs.
Replace if necessary with shaft, disc and screw assembly part no. Remove '"E" ring and slide throttle shaft fromcarburetor body. Inspect plastic throttle shaft forwear and replace if required with shaft, disc and screw as- sembly part no. Reassemble in reverse order making suresmall holeinthrottle disc is in- stalled facing reed plate assembly. NOTE Alwaysplace correct tension on throttle shaft spring when installing. Reed plate assembly may be cleaned with samesolventusedtocleancarburetor.
Exercisecarein handling reeds, so as not todistort them. Bent ordistorted reeds must be replaced. Check forexcessiveclearance between reedtip and reedplate as illustrated. Maximum allowed clearance. Reeds must be installed with rough edge away from plate as shown. This new carburetor is constructed of a special injection molded plastic material. An O- ringinstalled between thecarburetor and reedplateinsurespositivesealing.
The float and fuel valve is also a one-piece as- sembly. As fuel enters a single metered jet it is mixed with incoming air to form the cor- rect combustiblemixture. Theamount of fuel flow through the metering jet is regu- lated by the altitude needle.
Adjustment The governor will control the amount procedure is same as earlier D series of fuel entering the engine. The pur- carburetors. Refer to page for adjust- pose of theatmosphericpressure ment procedure.
An O-ring seals between theouter surface of the carburetor barrel and the inside di- ameter of the reed plate opening. The cor- rect procedure to install the carburetor is to lubricate the O-ring in groove of the reed plate and "plug" in the carburetor. When installingorremovingcarbu- retor from engine, the governor rod must be removedfromthethrottle arm.
The carburetorassembly is injection molded Check gasket forcracks or wear. Always plastic. DO NOT cleanusing a standarduse new gasketduringreassembly. Disassemblecarbure- tor components,washand cleanusing a goodNOTE grease solvent, dry andclean parts with compressed air - DO NOT dryusing a If any partappears worn o r damaged, cloth, lint may block passages impeding replace it.
To ensure properfloat proper carburetor operation. After cleaning, inspect all parts. Check After assembling float chamber to floatandfuelvalvesfor cracks or damage. Check float chamber for ment. If no sound movement is cracksor damage. Check dump valve and heard remove float chamber and re- gasket for distortion or damage. Check install correctly. It providesverticalpressuretothefloat and fuel valve forcing the fuel valve into the fuel inlet to stop the flow of fuel when the bowl hasfilled.
Each end of the spring is located in a recessedarea. The walls of these recesses provide guidance for vertical movement of the float and fuel valve. With- out these walled recesses the float and fuel valve would move laterallypreventingthe fuel valve from entering the fuel inlet seat squarely.
Mowing at an anglesuch as a terrace could result in a carburetor flooding without these recesses. As filter becomes saturated,in- coming air picks up more fuel,causing greater flooding. A puckered filter will allow air and dirt tobypassfilter. If oiled properly, filter is very efficient. First wash out with fuel, then apply 10 to 15 drops of oil. Squeeze several times todistribute oil. To removegrasp the detachable cover, loosen snap and fold cover down.
Reinstall filter in the same position which it was removedtoprevent imbedded particlesin intake side from entering carburetor. A pneumatic primerforcescompressedair intothefloat bowl chamber which forces fuelintothe carburetor venturi. This will preventthe starter pulley fromdam- agingthe hoses. Exercisecare when in- stalling hoses. Leavesufficient slack in hoses to prevent contact with starter pulley. Properhoseroutingrequiresthehosesto be parallel with eachother as shown.
If twisted, it is possible for hoses to be dam- aged by starter pulley. Exercise care when installing hoses. Examine vent hole in gas cap. Make sure it is not restricted. Remove air filter element. Watch nozzle in barrel of carburetor and push primer bulb down rapidly. If spurting of fuel is not visible. Remove fuel line from carburetor to determine if fuel is flowing from tank thru tank filter, valve and hose.
If not, remove hose from tank valve. Turn valve on to determine if fuel is flowing from tank. If so, restriction is in fuel hose. Wash out in sol- vent and blow with compressed air. Check function of primer bulb A. Place finger over lower end of primer hose and and hose. Resistance should be noted in bulb depression. Remove finger, there should be no resistance present when bulb is depressed.
Depress primer bulb and place finger over end of hose. The bulb should remain collapsed. If not, replace primer bulb and hose assembly. If fuel is spurting from nozzle, A. Check float valve and seat assembly. Check float level adjustment.
Re- move float chamber. Check to make sure movement of float and float arm is free. Check the throttle valve and shaft for freedom of movement. Remove metering nozzle and check for re- striction.
Blow out altitude air vent passage. Check setting and condition of reed valves. The new modular carburetor was introduced in the Ifengineis flooded,fuelcandrainback into filter. As filter becomes saturated, incoming air picks up This new carburetor is constructed of a special in- morefuel,causinggreaterflooding. A puckered jection molded plastic material.
The body and air filter will allow air and dirt to bypass filter. Make filter chamber is a one-piece plastic assembly which certain that filter covers cup area. First wash out withfuel, single screw. An O-ring installed between the car- then apply 10 to 15 drops of oil.
Squeeze several buretor and reed plate insures positive sealing. The times to distribute oil. A hinged type float of special cork material is sealed with an epoxy. During inspection, if. The float in this new modular carbu- and fold cover down. As fuelentersasinglemetered jet it ismixedwith a incomingair to form the correctcombustible mixture. Theamount of fuelflowthrough the metering jet isregulatedby the altitude needle.
The governor will control the amount of fuelentering the engine. Thepurposeof the atmospheric pressure adjusting needle is to mix the right amount of fuel with the correct amount of incoming air. Thisnewmodularcarburetor is also a Service replacement componentfor all pre- vious D-Seriesmodularcarburetors. A Quickvisualinspectionwillshowyou which modular carburetor ison the engine.
The modular carburetor is attached to the reed plate assembly by a single screw. Pull carburetor fromreed plate assembly. The carburetor assembly is injection molded plastic. DO NOTclean using a standard carburetor cleaner Disassemble carburetor components, wash and cleanusing a goodgreasesolvent,dryandclean parts with compressed air - DONOT dry using a cloth, lint mayblockpassagesimpedingproper carburetor operation.
Checkfloatand fuel valves forcracks or damage. Check throttle shaft, valveand spring for smoothoperation. Check float chamber for cracks or damage. Check 3. Check O-ring in reed plate assemblyfor damage. Checkair We recommend replacing O-ring every mowing ventpassagewhichallows air to flow intothe season and during all tune-up operations. Checkgasketforcracksor wear. An O-ringsealsbetween the outer surfaceof the carburetorbarreland the insidediameterof the reed plate opening.
If any part appears worn or damaged, re- place it. Use needlenose pliers to secure hinge on float arm to pin. The float valveconsistsofaneedleandseat as- sembly,activatedby a float in the carburetor bowl. Thesteelneedle is rubbertippedand the seatbrass. Thiscombinationeliminatespossible stickingandprovides a perfect seal. Theneedle rests on float arm, held in place by a spring clip. When float bowl is empty, float rests on bottom of bowl. As fuel enters bowl of carburetor, float rises, moving needle valve into seat and shutting off fuel.
As engine uses fuel,float dropsslightly,allowingmorefuel to enter bowl, maintaining a constant fuel level in bowl. Needle, seat and spring clip must be replacedas an assembly. They are matchedto form a perfect seal. Remove float bowl and examine float appearance. Float should be glossy because of epoxy sealer. If dullinappearance, or portions of epoxy have chipped away - replace float. Do not clean float with any type of sol- vent or carburetor cleaner.
Some of the problems you may encounter withthe float valve are as follows:. Remove float bowl and gasket. Invert carburetor. Obtain measurementsat two points at right angles to each other. If adjustment is required; using needle nose pliers bend float arm as shown. DO NOT bend float arm byapplyingpressure to float, this willdamage rubber tip on inlet needle. The float valve and seat must be replaced as an assembly. They are matched to form a perfect seal.
Remove hinge pin and remove float and valve. Remove spring clip securing valveto float arm. Check hinge on float arm to be sure it is secured to pin.
The hinge should be clamped tight enough so that the pin will swivel in the carburetor instead of the arm turning on the pin.
Tightening hinge to pivot pin will prevent inletneedlefrom not seatingcorrectly whenmowercrossesuneventerrain. Check pin clip on float arm by rotating carburetor sideways. If clipfallsoff float arm -- replace it. When reinstalling SEAT. Use caution when installing this needle as the seat, tighten securely. Exercise care when damagemayoccur to the carburetorbody orthe tightening seat to prevent damaging the seat. The altitude needle has a rubber O-ring around it to seal the threadsandpreventairfromleaking through.
It also serves as a locking feature to pre- vent the altitude needle from vibrating out of car- buretor body. The carburetor starts its action and op- 1. The crankshaftrotates when the starter erates as follows: rope is pulled or electric starter motor - engaged electric start models.
The rotating crankshaft moves the piston up and down in the cylinder. This creates pressure andvacuum alternatelyinthe crankcase. The vacuum created by movement of the pistonupwardin the cylinderopens a reed valve - then air rushes through the throat of the carburetor.
By inserting a tube from the carburetor float bowl into this center area, the dif- ference in air pressure will forcefuel up through this tube, where it is picked up by, and mixed with, the air. A pneumaticprimer forces compressed air into the float bowl chamber 7. A s fuel and air mixture enters the crank- which forces fuel into the carburetor venturi for case through the reed valves, it is near cold enginestarting.
Theengine, when cold, will not vaporize the mixture completely. A s the engine warms up, themixture is heatedinthecrankcaseandbecomes a consistently even gas. Float The float valve consistsof a needle and seat assem- bly activated by a cork float in the float bowl.
The needle rests on the float arm and is held in place by so a spring clip. The needle is rubber-tipped it will Thecarburetor is completelyautomatic. A s fuel enters a singlemeteredjet it is If the float bowl is empty, the cork float rests on mixed with incoming air to from the correct the bottom of the bowl.
As fuel enters the float combustiblemixture. Theamount of fuel bowl, the float rises, moving the needle into the flow throughthemetering jet is regulated seat, shutting off the fuel supply. As the engine by the altitude needle. All carburetorsrequire a finaladjustment of thealtitudeneedlepriortoputtingthe mower into service. To adjust, proceed a s follows: 1. CLIP 2. The 3. Observe adjustingneedle is to mix the right engine operation.
If not running smoothly,turn amount of fuel with the correct altitude needle counterclockwise approximately amount of incoming air. In the position no is the operation. Therefore, the float bowl pressure has been eliminated and the fuel 4. Slowly turn altitude needlecounterclockwise supply to the carburetor venturi is cut off, stop- until engine is running smoothly.
Allow engine ping the engine. After carburetoradjustment is com- pleted,shut off engine. It should start within 2 pullson starter handle. Fuel tanks must be vented to prevent vac- uum forming and stopping flow of fuel.
Tank caps will have a vent hole. A closed vent will create a vacuum in the tank as fuel is used - and eventuallycausethe engine to stop.
In a few minutes the vacuum will de- crease and the engine can be started again, but it will stopagainin a short period of BAFFLE time, The ventholecanbecome clogged with dirt, Check venthole beforeeach op- eration and clean if necessary. Replacethefuel shut-off assembly if damaged. The carburetor used on the early model F series engines is automatic. No fuel adjustments are nec- essary to regulate fuel intake. A single, meteredjet allows the correct amount of fuel to mix with the Shut-off valve is secured to fuel tank incoming air which is regulated by a single adjust- with a spring clip; exercise care ing needle.
Adjustment must be changed when a when re-installing to fuel tank. Two plastic plugsare available and recommended for installation inthe screw holes located in the back wall of the air filter box. Dirt then is prevented from enter- ing the air box. The part number is First wash out with fuel, o r solvent, blow dry with compressed air, then apply 10 to 15 drops of oil, Squeeze severaltimestodistribute oil.
If engine "smokes"for no apparent reason, filter may be saturated with fuel mix o r may need cleaning. On later production models the air filter cover was retained with a clipor bail. A dirty aircleaner element will create anoticeablepower loss, and may reduce engine life.
Operating engine without filterele- ment, or filter element without suf- ficientoil will shorten engine life. Reinstall filter in the same position which it was removedtoprevent imbedded particlesinintakeside from entering carburetor. On early models the air filter element MUST BE installed so the smalladdi- tional piece faces the venturi opening as illustrated. Also make sure it is positioned Squarely between both screw holes. If in- correctlyinstalled, the corner of the secondary filter will be drawn into carbu- retor throat thereby restricting air flow, resulting in a rich fuel mixture entering the engine.
Later production, this small square piece filter was eliminated. Thecarburetor is completely automatic. Slowly turn altitude needlecounterclockwise combustiblemixture.
Theamount of fuel until engine is running smoothly. Allow engine flow through themetering jet is regulated to run for one or two minutes to make sure by the altitude needle. Thereare no adjustmentstobemadeto 5. There is anatmos- operation. After carburetor adjustment is com- tobemade if theengine is operatingin pleted,shut off engine.
It should start of thealtitudeneedlepriortoputting the within 2 pullson s t a r t e r handle. Check mower into service. If not running smoothly, turn amount of fuel with the correct altitude needle counterclockwise approxi- amount of incoming air.
A pneumatic primer forces compressed air into the float bowl chamber which forces fuel into the carburetor venturi. NOTE A leaking primer will cause hard starting and a surging operation. Always adjust the governor to operate engine be- tween R. This w i l l seats lightly. After each movement of needle valve, wait for the engine to respond to the adjustment. Do not force it against the seat as it can become damaged.
Observe engineoperation. If not runningsmoothly, readjust needleslightly. Recheckhigh speed 2. After seating, turn counterclockwise 2 full operation again. Start and run engine to warm it up to normal 5. After carburetor adjustment is completed, shut operating temperature. It R. If difficult to restart, turn alti- and even.
Examine the primer assembly. A vent hole is lo- cated in the primer bulb of this fuel system. When the bulb is depressed, the vent hole will close and forces air through the primer hose into the carbu- retor for priming which forces fuel into up the ven- turi. Obtain measurements at two points at rightanglestoeachother. If adjustment is required; using needle nose pliers bend float a r m a s shown.
DO NOT bend float a r m by applying pressure 'to float, this will damagerubber tip on inlet needle. Checkpin cliponfloat arm by rotating carburetor sideways.
If clip falls off float arm -- replace it. The Nozzle Filter will provide a secondary filtering device to minimize the possibility of "fuzz" o r other minute particles getting into the carburetor area, which causes engine stalling, including hard restarting after shut down. Makesure the nozzle is free from dirt prevent inlet needle from not seating - and "fuzz" then install filter on the nozzle. Hold correctly when mowercrosses un- float upand lift bowl carefully in place. For easier even terrain.
This condition is installation,takecarburetor off andturnupside called "fluttering. The steel needle is rubber tippedandthe seatbrass. This combina- tioneliminatespossiblesticking and pro- vides a perfectseal.
Theneedle rests on float arm, held inplace by aspring clip. When float bowl is empty, floatrests onbottom ofbowl. As fuel enters bowl of carburetor, float rises, moving needle valveinto seat andshutting off fuel. Oss inherenl in a turbocharged engin a is s ubslantialiy less than lhe ncurred by dri vin g a supcrchm'gcr with tI. Quantity of offers presently founded - two. This is a image galleries about Lawn Boy can also find other images like wiring diagram, parts diagram, replacement parts, electrical diagram, repair manuals, engine diagram, engine scheme, wiring harness, fuse box, vacuum diagram, timing belt, timing chain, brakes diagram, transmission diagram, and engine problems.
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