
(2)Next,intheconditionof(1),fullyopenthethrottlevalve,turnbackthemainneedletomaketheair-fuelmixtureveryrichin
therangewheretheenginedoesnotstall(about4,000rpm).Operateinthisconditionwith2(ormore)tanks.(Conductthis
stepcheckingthedensityoftheexhaustandthebreatherʼswasteoil(inky-blackwasteoil)).
(3)Next,afterfillingupthetank,re-starttheengine.Withthethrottlevalvefullyopened,throttlethemainneedleandoperate
theengineforonetankat7500‒8,000rpm.
(4)Next,afterfillingupthetank,re-starttheengine.Withthethrottlevalvefullyopened,turnthemainneedlefromtherichto
thepeaksseveraltimes.Whenthepeakbecomestable,openthethrottlevalvefromlowspeedtohighspeedseveraltimes
tochecktheresponse.Andgraduallyelongatethetimeofhigh-speedoperation.Conductthisoperationforonetank.
(5)Whentherevolutionisstabilizedatpeak,theground-levelbreak-iniscompleted.Afteradjustingthetappetgapinthe
mannerofsection“14”,adjustthecarburetoraccordingtothefollowingsection.Therunning-iniscompletedbyperforming
some20flightsinalittlerichcondition.Subsequently,theflightshouldbeperformedinsucharichconditionasfarasnotto
influencetheflight.
13.Adjustmentofcarburetor
Theprincipalmethodofadjustmentisthesameasthatforourglowengine.
Inprinciple,acarburetorisadjustedbyfirstachievingpeak(thehighestrevolution)withthemainneedleandthensetidling
(lowspeedrevolution)withthethrottlevalveandtheslowneedle.(Unlessthepeakiscertainlyachieved,idlingadjustmentwill
bedifficultandnotstabilized.)
(1)Afterfillingupthefueltank,starttheengineinthemannerofSection“11”andthenfullyopenthethrottlevalvewiththe
throttlestick.
(2)Byturningthemainneedledependingonthetachometerandtheexhaustsound,achievepeakcarefully.
*Asforadjustingthemainneedleinthecaseofactualflight,settingthepeakintheperpendicularattitudewithapropeller
intheupwarddirectionisrecommendedifitʼspossible.Inthatadjusting,itʼllberichenoughinthehorizontalattitudeso
itʼsmoresimilartotheconditionduringtheactualflight.
(3)Next,closethethrottlevalveuntiltheengineoperatesstablywithanidlingrotationofaround2000-2500rpm,adjusting
theslowneedlewiththe(-)screwdriverandthethrottlevalvecarefully.
*Sincetherichnessleveloftheair-fuelmixturevariescorrespondingtothenatureoftheairframe,pleaseadjustitdepending
ontheuserʼsskill.
Generally,inascaleflightinwhichthestabilityofalow-speedzoneisconsideredasimportantandtheengineisoperated
slowly,adjusttheair-fuelmixturetoberelativelylean.Inanacrobaticflightinwhichtheearlystand-upfromalowspeedis
consideredasimportant,adjusttheair-fuelmixturetobeslightlyrich.
(4)Aftertheidlingisset,getthethrottlevalveslowlyfullyopened.Iftherevolutionbecomessloworgoesupsuddenly,adjust
carefullyuntilitchangeslinearlyfromidlingtopeak,byfine-tuningwiththeslowneedle.
(5)Aftertheaboveadjustmentiscompleted,openthethrottlevalvefromidlingtopeakquickly.Iftherevolutiondoesnot
achievepeakimmediatelybutgetdelayedasthethrottlevalveisfullyopened,fine-tunethemainneedleandperformthe
sameprocessfromidlingtopeakquickly.Repeatthiscarefullyuntiltheresponseimproves.
*Thekeytomaketheenginelastforlonglifeisoperatingwiththeslightlyrichconditionasfarasitdoesnʼteffecttotheflight.
Adjustmentisneededdependingontheengineattachmentdirection,thepropeller,thefuel,theplug,theclimatecondition,
etc.Duringflights,pleasefine-tunesothatlowspeed,mediumspeed,andhighspeedmatchbestwiththeairframe.
14.Normaloperation,maintenance,andadditionalinformation
(1)Justafterstartuptheengine,performwarmuprunninginrichconditionforabout1minute,andjustbeforestoprunitat
idlingfor1minutetocooldownaswell.
(2)Whenstoptheengineafterthefinalflightoftheday,besuretostopbycuttingthefueltoremovefuelfromthecarburetor.
Andremovethefuelfromthetankandreserveitwithspecialcare.
(3)Sincethefuelcontainsmorethan5%ofoil,sometimestheexhaustvalvegetsdullbycarbonorsludgeespeciallyincold
atmosphere.Thenturnofftheignitionswitchandrotatethepropbyelectricstarter.Afterdilutetheoilcontentbythisway,
removethefuelfrominsidethecarbandtheengine.Ithelpsthevalvetomovesmoothly.
Or,removetherockercoverandapplyingsomeanti-rustspraytotheexhaustvalveiseffectiveaswell.
(4)Lubricationforpiston,connectingrod,bearingorcamgearisablow-bylubricationinwhichtheoilinthefuelgoesintothe
crankcasefromtheclearancebetweenthecylinderandpiston.Thereforetheenginelifeisaffectedbythepropertyofthe
fueloil.Pleaseusehighqualityoil.
(5)ChargethebatteryfortheignitionsystemandRCdevicefully.(Sincetheignitionsystemgenerateshightension,becareful
ofelectricalshock.)
(6)Sinceoverclosingthemainneedlecausesoverheating,adjustalittlemorerichthanpeak.Overclosingleadstoknockingor
overheatandhasanadverseeffectontheconnectingrodandcamgear.Wheretheairplaneachievespeakcompletelyat
thetimeofascentshouldbeaproperpeakoftheengineduringflight.
(7)Whenconnectingtheexhaustpipetothecylinderorattachingthepropnut,applythincoatofsiliconrubber(notexces-
sively)oradhesiveonthethreadsectionbeforetightening.Thispreventsleakageorloosening.
(8)BecauseallofSAITOgas-enginesuseoil-fuelmixture,theretendtobecarbonbuildupinside
themufflerasshowninthepicture.Itcausessomeproblemsontheexhaustoutletand
consequentlyreducesthepower.Thereforecleaning/removingcarboneveryabout50flights
isrecommended.Usingapartscleaningsprayiseffectiveway.Actually,itdependsonthe
qualityoftheoilsowhenyoufeelthepowerloss,pleasecheckinsidethemuffler.
Inthecaseofthepicturewhichhadbeendonemorethan70flights,byremovingthecarbon
buildup,thesmoothnessoftheengineimproveddramatically.
-5-
Note:Duringearlystageofflights,taketheheighthighenoughtolandsafelyincasetheenginestopintheairsuddenly.It
willreducetheriskofcrashorlandingaccident.
Caution:Overclosingthemainneedleisverydangerousbecauseitmaycauseknockingandpropellernutloosening.Then,
turnthemainneedleCCWimmediatelytomakeitrichalittle.