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Honda Common Service Manual

1. Be sure that the throttle valve cutaway is toward the air CUTAWAY STARTER VaLve VALVE NUT VALVE SPRING HONDA MOTOR CO LTD 8 17 FUEL SYSTEM AUTO BYSTARTER Apply a small amount of grease to the O ring and install the auto bystarrer inta the carburetor hody Refer to the Model Specific manual for the auto bystarter installation angle Secure the auto bystarter with the set plate and screws Install the auto bystarter cover CARBURETOR SEPARATION ASSEMBLY INSTALLATION Refer to the Modet Specitic manual for carburetor separa tlon assembly Check ond adjust the carburetors as described bolow after the assembly Move the choke arm by hand and be sure that the starter valve operates smoothly Rotate the throttle drum and be sure that all the throt open and close smocthly valves Turn the throttle stap screw to align the throttle valve with the edge of the by pass hole in the base carburetor Base car buretor is the one on which the throttle stop screw is installed Refer to the Mada Specific manual Align each throttle valve with the by pass hole edge by turning the synchronization adjusting screws Refer to the Mode Specific manual for the location of each synchronization screw Install the carburetor and adjust the synchronization PILOT OR AIR SCREW ADJUSTMENT PILOT OR AIR SCREW REMOVAL NOTE gt Ae i pot or av soraw air a at
2. 3541 into the drilled plug and continue tuming the screwdriver until the plug rotates with the screw Pull on the screw head with pliers to remove the plug Use compressed air to clean the screw area and romove metat shavings Turn the screw in and carefully count the number of turns until it saata lightly Make a note of this to use as a reference when rainstalling the screw CAUTION Tightening the pilot or alr screw againat its seat weit damage tho saat Remove the screw and inspect it Replace it if it is wom or damaged Date of Issue Sep 1988 HONDA MOTOR CO LTO WASHER SPRING LIMITER CAP PILOT SCREW CARBURETOR FUEL SYSTEM PILOT OR AIR SCREW INSTALLATION CARBURETOR Install the screw and return it to its original position as noted during removal Perform the pilot screw or air screw adjustment if a naw screw is installed NOTE I you replace the pilot acrew in one carburetor you must replace the pilot screws in the other carburetors for pro per pilat screw adjustment Do not install a limiter cap or plug over a pilot or air __sctew untit the screw has been properly adjusted PILOT SCREW ADJUSTMENT IDLE OROP PROCEDURE 4 stroka multi carburator eris slons contrai applicable models NOTE Moke sure the carburetor synchronization i within Specification before pilot screw ad
3. the pump s diaphragm Is depressed by the pump rod Ar this time the inlet check valve is shut so the pump chamber undergoes a rise in pressure The outlet check valve is then opened and fuel is supplied to the main bore via the pump hole As the throttle valve is shut down the accalerator pump s diaphragm is returned by spring action At this time the inlet check valve is openad and fuel from the float chamber enters the pump chamber The outlet check valve is closed at this Point to prevent air being drawn in through the pump hols AIR CUT OFF VALVE When the throttle lever is turned in the close engine braking is applied the fuel mixture becomes ignited air fuel mixture is discharged into the exhaust pipe resulting the afterburn To prevent this afterburn cut off valve shuts the air passage to the slow jet to temporarily make the fuel mixture rich With the throttle valve closed and the vacuum in the main bore increased vacuum in the air cut off valve also increases and moves the diaphragm to shut the air passage With the vacuum in the main bare decraased the spring moves the diaphragm backward and opens the air passage REED VALVE INSPECTION Refer to the Model Specific manual for removal nstallation Check the read valve for fatigue or demaga and replace the reed valve assembly if necessary Check the reed valve seat for cracks damage and clearance from the raed and replace the reed valve ass
4. adopt a common exhaust pipe for all cylinders The new system features a system in which the exhaust pipes join in tha exhaust chambar and another in which the exhaust pipas are directly joined In both systems gas pressures ex hausted from individual cylinders intermingle The pulse wave in the muffler generated by the staggered combustion in ad joining cylinders promotes the pulsa scavenge effect which increases exhaust energy absorption and reduces ex haust noise affectively Tha resuiting smaller muffler has a decreased capacity and increased silencing capability due to the reduced weight and decreased volume The method of exhaust pips connection depends on the cylinder arrangement or the required engine characteristics For exampte an inline four cylinder engine can be connected with 4 into 1 system or 4 2 2 system etc AIRIFUEL MIXTURE PRESSURE WAVES TAPER OF THE EXPANSION CHAMBER 4 into 1 EXHAUST Date of Issue Sep 1988 HONDA MOTOR CO LTD 7 EMISSION CONTROL SYSTEMS SERVICE INFORMATION 7 1 SYSTEM INSPECTIONS 7s TROUBLESHOOTING 7 1 EMISSION CONTROL INFORMATION i SYSTEM DESCRIPTIONS E TABELS R SERVICE INFORMATION ar ra To All hoses used in the secondary air supply and evaporative emission control systems are numbered for identification When connecting one of these hoses compare the hose number with the Vacuum Hose Routi
5. be no more than six to eight weeks old in the case of a minor performance problem and no more than three months ald in the case of more serious performance problems Date of tsue Sop 1988 8 1 HONDA MOTOR CO LTD FUEL SYSTEM TROUBLESHOOTING Engine won t start No fuel to carburetor Fuel strainer clogged Fuel tube clogged Float valve stuck Float level misadjusted Fuel tank breather tube for hole clogged Fuel pump malfunction Fuel auto valve malfunction Too much fuel getting to the engine Air cleaner clogged Flooded carburetor Intake air leak Fuel contaminated deteriorated Slow circuit or bystarter circuit clogged Lean mixture Fuel jats clogged Float valve faulty Float levet too low Fuel line restricted tar am vent hole or tube clogged ir leak Fuel pump malfunction Fuel auto valve malfunction Vacuum piston faulty CV type only Throttle valve faulty Rich mixtur Choke valva or bystartar valve in ON position Float valve faulty Float level too high Air jets clogged Air cleaner element contaminated Flooded carburator Hasitation during accelaration Accelerator pump malfunction Engine stalls hard to start rougi Fuel line restricted Ignition malfunction Fuel mixture tao leanitich Fuel contaminated detariorated Intake air leak Idle speed misadjusted Fuel pump malfunction Fuel auto valve
6. it indicates the diaphragm is incorrectly installed or damaged If the vacuum remains steady but the fuel flow is not smooth it indicates a clogged filter or incorrectly installed diaphragm 3 If the tuel flows without the vacuum applied the diaphragm is incorrectly installed Refor to the Model Specific manual for replacement procedure CARBURETOR DISASSEMBLY INSPECTION NOTE Refer to tha Model Specific manual for carburetor removal and disassembly separation THROTTLE VALVE BYSTARTER VALVE INSPECTON Move each valve and be sure that it operates smoothly Check the throttle valve shaft for play Push the relief valve if it is installed on the throttle valve and bbe sura that it opens and closes smoothly THROTTLE VALVE INSPECTION CV type Rotate the throttle drum and be sure that it operates smoothly Check the throttle valve shaft for play STARTER VALVE THROTTLE VALVE PIVOT ff i ca THROTTLE DRUM THROTTLE VALVE j Date of Issue Sep 1988 HONDA MOTOR CO LTD 8 9 FUEL SYSTEM AUTO BYSTARTER VALVE AUTO BYSTARTER Connect an ohmmeter to the auto bystarter wire connector terminals and measure the resistance if the resistance is greatly out of specification it indicates a faulty PTC in the auto bystarter Replace the auto bystarter NOTE The auto bystarter might be normal if the resistance is only slight
7. pre vent air leaks While applying vacuum to the AVCV hose thet goes to the vacuum tube fitting apply air pressure to the air vent fitting It should hold steady Feplaca the AVCY if pressure is not retainad Remove the pumps install the AVCV on its mount route and reconnect the hoses according to the vacuum hose routing diagram label in VACUUM PLUG PUMP PRESSURE PUMP Date of Issue Sep 1988 HONDA MOTOR CO LTD 7 7 EMISSION CONTROL SYSTEMS SECONDARY AiR SUPPLY SYSTEM AIR CLEANER CASE acy Start the engine and warm it up to operating temperature Stop the engine and remove the air cleaner element Check that the secondary air intake ports are clean and froe of carbon deposits Check the raed valve in the secondary air passage if the ports are carbon fouled SECONDARY AIR INTAKE PORT REED VALVE Disconnect the air cleaner to air injection control valve hose from the air cleaner case VACUUM PUMP Ramove the vacuum tube from the carburetor intaka pipe in stall a plug to keep air from entaring Connect a vacuum pump to the vacuum hose VACUUM PUMP ST AH 260 MC7 i U S A onty Start the engine and open the throttle slightly to be certain that air is sucked in through the air cleaner to AICY hose If gir is not drawn in check the air cleaner to AICV hose and vacuum hose for clogging
8. section of the jet needlo regulates at 1 8 1 2 and the jetnee C yg yg T 7 za dle clip position or jat needle tapered section diameter regulates at 1 4 3 4 When the throttle is fully open actually dond on arange of 1 2 fully open the fuel is regulated by the main jet of the main system Float system The float chamber holds a constant level of fuel in order that FUEL FLOAT VALVE the engine may be provided with a stable supply of the re N Certain height quired air fuel mixture As fuel is consumed and the level in the chamber falls the i float and float valve are lowered and the chamber is i 6 mediately refiled to a specified level A rise in tuel level causes the float and its valve to rise the valve contacts the valve se and the tuel supply is cut ofl This operation is repeated con tinwally as the engine is run OVERFLOW TUBE FLOAT ARM FLOAT The float valve contains a spring which lightly depresses the valve so that it does not become dislodged from the seat by vibration when the vehicte is running To keap the inside of the float chamber at atmospharic pressure there is a connection to the outside of the carburetor known as the air vant passage FLOAT VALVE An ovectiow tube is provided to vent off any excess fuel tothe mong outside of the carburetor should the valve and seat become Separated due to the intrusion of dirt or othar foreign matter L VALV
9. stow JET Date of Issue Sep 1988 HONDA MOTOR CO LTD 8 5 FUEL SYSTEM Fiston valve type throttle valves have a cut out on the intake THROTTLE VALVE PISTON VALVE TYPE side The larger the cut out the greater the volume of air entering and the leaner the mixtura cuT ouT STAMP indicates cut out The larger the number is the leaner the mixture becomes Main system medium throtvia opening When the throttle valve is opened to raise the engine speed a greater volume of air fuel mixtura is required than for idling The carburetor is aquipped with the main system for this pur pase The degree of opening of the throttle valve is divided into two stages With a degree of opening 1 8 1 2 the air flow in the main bore facilitates a drawing up of the fuel from the gap between the jet neadie and needle jet isee Carburetor Theory The fuel it which has entered the air bleed hole of the needle jet holder trom the main air jot JET HOLDER With a degree of opening 1 4 314 the fuel drawn from the Saas LARGE tapered section of the jet nevdle is regulated The greoter the CLEARANCE CLEARANCE valve opening the further the tapered jet needle rises incroas Fuel pesssge H ing the cross sectional area for fuel passage and thus the is narrow volume of fuel supplied In piston type throttle valves the jet i NEEDLE JET needa contains clip grooves in fiva s
10. to tho specified opening Refer to the Model Specific manual tor standard and high altitude setting NOTE This adjustment musi be made at high altitude to ensure Proper high altitude operation On some models the standard main jet must be replaced i Mith an optional smaller high altitude fet Attach Vehicle Emission Control Information Update Label in he location specitiad in the label position illustration Refor to the Model Specific manual for the specified position NOTE gt Do not attach ihe label to any por that Gan be ensiy L_temoved from the vahicie cmm Operation at an altitude tower than 6 000 feet 1 500 m the carburetors adjusted for high altitudes may use the engine to idle raughly and tha engine may stall in traffic Bi When the vehicle is to be operated continuously below 5 000 feet 1 500 m turn the pilot scraw counterclockwise ithe ev Screw clockwise to its originat position and reinstall the star dard main jet as necessary and adjust the idle speed to the Specified rpm sree LE UPDATE LABEL YORCLE EIMISSIDN CONTROL PMFORMATIDN UPDATE ANDA MITOR Ce UTD Ts vouca was Been avsto mo C IMPROVE EMISSION CONTROL PERFORMANCE WREN GPERATED AT MIGH ALTITUDE Ww ALTITUDE PERFORMANCE ADIUSTMENT WSTRUCTIONS ARE AYAILABLE AT YOUR AUTRORIZED WONDA DEALER Ba sure to make these adjustments at low altitude 24 Date of Issue
11. Air scrow tha limiter cap position permits counterclockwise LIMITER CAP rotation and prevents clockwise rotation NOTE Do not tur the pilot screw or air screw when installing _the limiter cap LIMITER PLUG Drive new pilot screw tor air screw plug into the pilot screw for air screw bore with a 7 mm valve guide driver PIN 07942 82300 When fully seated the plug surface will be recessed 1 mm LIMITER PLUG Date of Issue Sep 1988 HONDA MOTOR CO LTD 8 23 FUEL SYSTEM ACCELERATOR PUMP ADJUSTMENT PUMP ARM NOTE Accelerator pump adjustment L__the adiusting screw is replaced Adjust the idle speed is not nacessary unless J Adjust the throttle grip frae play Measure the clearance betwen the accelerator pump rod and pump arm CLEARANCE Refer to tho Modei Specific manual i the clearance is not within specification adjust the Clearance by carefully bending the pump arm or by turning the adjusting scraw Refer to the Model Specific manual HIGH ALTITUDE ADJUSTMENT U S A only Whan the vehicle is to be operated continuously above 6 500 eat 2 000 m the carburetor must be readjusted as follows to improve driveability and decrease exhaust emission Warm up the engine to operating temperatura Ten minutes of Stop and go driving is sufficient Turn the pilot screw clockwise to the specified opening or tuen the ale screw counterctockwise
12. Be carefu not to pinch the diaphragm and to keep the spring straight ta i 8 16 FLOAT LEVEL GAUGE VACUUM PISTON WASHER SPRING HOLDER RD JET NEEDLE JET NEEDLE OLDER SPRING tL Align Date of issue Sep 1988 HONDA MOTOR CO LTD THROTTLE VALVE Piston valve type NOTE Cablie operated throttle valva type carburetor lahronie valve is connected to the cabie via tha link Refer to the Model Specific manua for throttie valve removal disassembly Install the clip on the jet needte Refer to tha Model Specific manual for the standard clip position Install the jet needle into the throttle valve and secura with the ratainer Route the throttfa cable through the spring and compress the spring fully Attach the throttla cable end to the bottom of the throttle Valve and thread the throttia cable through the slot in the valve Align the cutout in the threttia valve with the throttie stop screw on tha carburetor body and install the valve on the carburetor NOTE cleaner case side as it determinas tha volume of air tor fuel mixture BYSTARTER VALVE MANUAL Install the starter valve spring and nut ep 1988 FUEL SYSTEM clip is set in the grooves tha richer tha mixture becomes JET P NEEDLE E t cir RETAINER cuip Jer NEEDLE THROTTLE VALVE
13. E PIN To improve starting when the engine is cold and the fuel is not sufficiently gaseous the carburetor is equipped with either Ain FLOW choke or bystarter to enrich the mixture lt Choke system gt A valve is fitted to the air cleaner side of the carburetor The valve is shut down during starting to reduce the mass flow of sir and create an increase in negative pressure in the main bore The resulting mixture is rich having a proportionally low CHOKE VALVE volume of air The choke valve is provided with a raliat mechanism which en sures the optimum opening af the valve under conditions of negative pressure above a certain level thus preventing the supply of an over tich mixture to the engine Dt atone Bon TOES 8 4 HONDA MOTOR CO LTD FUEL SYSTEM lt Bystarter system manuall gt As the bystartar is opened the bystarter circuit connects with the main bore As a vacuum is created in the main bore on star ting air and fuel drawn from the bysterter ait jet and bystarter fuel jet respectively are injected into the main bore to supply a rich mixture lt Auto bystarter system gt The auto bystartar PTC is a device for increasing the volume of tuat itis comprised of components such as a heating element thermo wax a liquid medium piston and the bystarter valve The principle of operation is as follows When the ehgine is stopped and there is no production of cur rent from the altern
14. IVE EMISSION CONTROL SYSTEM California model only Check the system hasas for deterioration clogging damage and loose joints and connections Replace any hose that shows signs af damage or deterioration Check the canister for cracks or damage PURGE CONTROL VALVE PCV NOTE The purge control valve should be inspected if hot restart is difficult Disconnect the PCV hosas trom their connections and remove the PCV from its mount Reter to the vacuum hose routing diagram label for hose connections Connect a vacuum pump to the hase that goes to the vacuum tuba fitting Apply the specitied vacuum to tha PCV VACUUM PUMP ST AH 260 MC7_ USA ont SPECIFIED VACUUM 250 mm 9 8 in Hg The specified vacuum should be maintained Replace the PCV if vacuum is not maintained Remove the vacuum pump and connect it to the hose fitting PCY output port that goos to tha carburetors NOTE L M he FGV hes two hose fittings that go to the cor turetorsh connect tbe blocked tube ente the other fn Sng to prevent a les Apply the specified vacuum to the PCV SPECIFIED VACUUM 250 mm 9 8 io H9 The spocifiad vacuum should be maintained Replace the PCV it vacuum is not maintained TO CARBURETOR PCV OUTPUT PORT Date of Issue Sep 1988 HONDA MOTOR CO LTD 7 5 EMISSION CONTROL SYSTEMS Connect a pressure pump to the hose fitting that goes to the cha
15. NIN lefer to the Madel Specific manual 9 Readjust the idle speed with the throttle stop screw 10 Install the new limiter cap tor plug onto the pilot screw head page 8 23 FUEL SYSTEM PILOT SCREW Date of Issue Sep 1988 HONDA MOTOR CO LTD 8 21 FUEL SYSTEM AIR SCREW OR PILOT ADJUSTMENT A BEST IDLE PROCEDURE 4 stroke all modais NOTE The air or pilot scraw is factory pre set Adjustment is ner necessary unless the carburetor is overhauted or a new air or pilot sarew is installed h CAUTION tid the a or ior saron agin HE we wi damage tho see i 1 Turn the air or pilot serew clockwise unti it seats lightly then back it out to the specification given This is an initicl Setting prior to the final at oF pilot scraw adjustment AIR OR PILOT SCREW OPENING Refer to the Modal Specific manual 2 Warm up the angine to operating temperature Ten minutes of stop and go driving is sutticient 3 Stop the engine and connect a tachometer 4 Stor the engine ond adjust the idie speed with the throttle stop screw IOLE SPEED Refer to the Model Specific manual 5 Tum the ait or pilot scraw in or out slowly to obtain the highest engine speed 6 Readjust the ilu speed to the specified value with the throt tle stop screw 7 Make sure that the engine does not miss or run erratically Repeat steps 5 and 6 until engine speed increases smoothly 8 Readj
16. OTE Chack the fiat eval after checking the Hast valve aaa float ipage 8 131 Sot the float level gauge so that it is perpendicular to the float chamber face and in line with the main L Sot the carburetor sa that the tip of the float valve just con ects the float arm lip Be sure that the float vaive is securely in contact with the valve seat Measure the float level with the toat level gauge FLOAT LEVEL GAUGE 07401 9010000 If the level is out of specification and the float arm lip can be bent adjust the float leval by bending the lip Non adjustable floats must be replaced NOTE Ba sure to keep the font level a th ecified height the float level is low high fuel mixture becomes L_loanvtich VACUUM PISTON CV type install the washer on the jet needle and instal the jet needle in tha vacuum piston install the spring holder with its pawts aligned with the Srooves in the piston if installed Install the spring Turn the jet needle holder clockwise while pressing it into the vacuum piston until it locks Projections on the vacuum piston end jet needle holder should be aligned after turning Install the vacuum piston on the carburetor body Lift the bottom of the piston with your finger to set the diaphragm rib in the groove in the carburator body Install the spring Install the vacuum chamber cover with its cutout aligned with the hole in the tab of diaphragm NOTE
17. Sep 1988 HONDA MOTOR CO LTD
18. With the engine running gradually apply vacuum to the vacuum hos REED VALVE HOSE Check that the ir intake port stops drawing air end that the AIR CLEANER TO AICVI vacuum does not bleed SPECIFIED VACUUM Refer to the Model Specific manual If air is still drawn in or if the specified vacuum is nat maintair ed install a new AICV If attarburn occurs on deceleration even when the secondary air supply system is normal check the slow air cutoff valve for correct vacuum operation _ 7 8 Date of Issue Sep 1988 HONDA MOTOR CO LTD REED VALVE NOTE Certain types of secandary air supply systems have the reed valve built in the AICV Refer to the Model Specific manual far reed valve location Remove the reed valve covers and read valves Check the reeds for damage or fatigue and replece if necessary Install a new reed valve if the seat rubber is cracked or damag ed or if thare is clearance between the reed and seat CAUTION Disassembling or bending the reed stopper ar raed valve will damage Replace the seat is faulty jed valve as a unit If the stopper reed or EMISSION CONTROL INFORMATION LABELS Labels for the emission control system consist of three kinds of information labels as described below 1 Emissian control information label Gives basic tune up specifications 2 Emission control information update tabet After making a
19. ator the starter valve is maintained in the raised position by a spring tn this position the tu cuit is fully open ready for supply at any tima When the engine starts fuel is supplied through the fuel in iterator sends current 10 the PTC for heating The increase in heat is sensed by the thermowex which begins to expand The movement is transmitted through the liquid medium to the piston set collar and set spr ing and the startar vatve is depressed As the valve is lowered the jet needte starts to shut off the fuet increase circuit which aftar a taw minutes closes fully ending fuel compensation Slow system flow dagrea of oper As the throttle valve is only slightly opan at tow engine speeds degree of opening fully closed 1 4 pressure on the intake side is low which allows some residual gas from combustion being sucked back into the intake manifold where it is mixed with fresh charge from the carburetor The resulting mixture is lean Low engine speed is linked with lower compression in the cylinder resutting In a richar mixture and it is necessary to raise the combustion velocity For this purpose the engine includes a slow fuel supply system which is separate from the main system AIR FLOW BYSTARTER AIR JET BYSTARTER FUEL JET From PTC HEATER ALTERNATOR THROTTLE VALVE SLOW AIR THROTTLE STOP SCREW BY PASS AIR SCREW
20. bove problems the exhaust gas is drawn from the exhaust port into the muf fier to be swelled and is discharged into the atmosphere after its temperature and pressure are lowered By varying the sizes and diameters of sections of the exhaust system the air fual mixture can be drawn into the cylinder more effectively Thus is called the EXHAUST PULSE SCAVENGE EFFECT Utilizing this effect in exhaust system design results in si ignificant im provements in engine performance especially on 2 stroke engines EXHAUST PULSE SCAVENGE EFFECT INTAKE VALVE OPENS Whon the exhaust valve or port opens with the engine on the exhaust s the exhaust gas flows rapidiy from the ex haust port into the muffier At the end of the exhaust stroke an the gas flow slows down but due to the inertia of liquid mass in the cylinder goes down below the atmospheric Pr in other words negative pressure is applied to the cylinder for a short tim As the Intake valve or scavenge port opens the air tuet mixture quickly drawn into the cylinder NEGATIVE PRESSURE AT END OF EXHAUST STROKE The discharged gas flows through the muffler forming a high EXHAUST VALVE OPENS speed pressure wave Due to the inertia of liquid mass negative pressure is applied to the exhaust port where the pressure wave hed passed When the exhaust valve or port opens on the next exhaust stroke the exhaust gas is drawn out by the negative prossure and the exhaust e
21. e cover on the float chamber being careful not to pinch the diaphragm Adjust the accelerator pump page 8 24 FLOAT JETS ASSEMBLY NEEDLE JET Install the needie jet neadie jet holder main jet slow jet thot THROTTLE ta stop screw and pilot or srt screw on the carburetor body STOP SCREW CHAMBER Tighten the pilot or air screw until it seats lightly then turn it SIDE eut as much as the number recorded during removal NEEDLE JET HOLDER CAUTION d f Tightening the pilat tor air screw against ts seat enian i D sent pers 3 MAIN JET iti Phot screw Slow Jer le jet with the smaller hole j Bo sura to install the ne toward the float chambs Install the pilot ar air screw and its O Sere the order as shown in the drawing If the screw and carburetor body a ones adjustment is necessary Motercyctes with emission control systems Refer to page 8 20 for the pilot or air scraw instal only Install the float tloat vatve and float pin FLOAT VALVE FLOAT PIN O RING Install the O ring on the float chambar and tighten the flost chamber with the screws NOTE Wf the toat valve must be hung krom iho Haat arm tip Note the installation direction of the float valve FLOAT CHAMBER Date of Issue Sep 1988 HONDA MOTOR CO LTD 8 15 FUEL SYSTEM FLOAT LEVEL INSPECTION MAIN JET N
22. e for scores scratches or wear and repioce if necessary Check the seat at the tip of the valve for stepped wear and STARTER VALVE NUT replace if necessary SPRING If the valve seat is worn or damaged it will not close the fuel it resulting in ii bia ate bveterter circuit rasuting in a constantly rich fuet eae starter vatve THROTTLE VALVE Piston valve type CABURETOR TOP CAUTION Some carburetoricables have a one piece sro cable catburetor top assembly Do not try to remove the throttle cable from the carburetor top Remove the carburetor top and pull the throttla valve out of the carburetor THROTTLE VALVE While compressing the spring disconnect the throttle cable from the throttle valve THROTTLE NOTE If the throttle valve is linked to the cable refer to the Mode Specific manual for each model for removal L disassembly steps THROTTLE VALVE Date of issue Sep 1988 HONDA MOTOR CO 8 11 FUEL SYSTEM Remove the jet needle retainer and jet needte from the throttle valve Check the jet needle for stepped wear The fuel supply to the main circuit cannot be adjusted if the jet needle is worn VACUUM PISTON CV type Remove the screws vacuum chamber caver spring and vacuum piston assembly from the carburetor Check the piston tor smooth operation in the carburetor body Turn the jet ngedi holder counterclockwise
23. ee 6 EXHAUST SYSTEM SERVICE INFORMATION 61 SYSTEM DESCRIPTION e2 TROUBLESHOOTING 6 1 SERVICE INFORMATION warn 7 Serious burns may rasult If the exhaust system is not allowed to cool before components are removed or Always replace the exhaust pipe gasket when removing the exhaust pipe from the engine Note the positions of the clamps installed between the exhaust pipe and muffler the tab on the clamp should align with the groove on the muffler When installing the exhaust system install all the fastners loosely Always tighten the exhaust clamp nut first then tighten tha mounting fastners If you tighten the mounting fasteners first the exhaust pipe may not saat properly Always inspect the exhaust system for leaks after installation TROUBLESHOOTING Excessive exhaust noise Broken exhaust system Exhaust gas leaks Poor performance Deformed exhaust system Exhaust gas leaks Clogged muttier Date of Issue Sep 1988 641 HONDA MOTOR CO LTD EXHAUST SYSTEM Ts SYSTEM DESCRIPTIONS The exhaust system serves other function in addition to discharging the exhaust gas Since the exhaust gas discharged from tha exhaust part is pressurized and very hot it swells suddenly and produces a loud noise if it is discharged from the exhaust port directly into the atmosphere It also lowers the exhaust efficiency as the gay is diffused from the exhaust port To prevent the a
24. embly if necessary NOTE Ba Sure ta replace the reed valve as en assembly Disassembling or bending the reed stopper will cause engine trouble Throttle valve opens ACCELERATOR NOZZLE ed OUTLET CHECK VALVE ay ETTE oad CHECK eae INLET ACCELERATOR PUMP DIAPHRAGM e Throttle valve closes i VACUUM CHAMBER DIAPHRAGM AIR PASSAGE This moves to the left to shut up the air passage REED STOPPER Date of Issue Sep 1988 HONDA MOTOR CO LTD FUEL SYSTEM FUEL LINE FUEL TANK CAP NOTE X FUEL FILTER Refer t section Z fr fual fer inspection J 1 Check the fuel tank cap and or fuel tank breather tube for clogging ino breather tube on California on road models 2 Visually inspect the fue strainer for contamination Check the fuel flow with the fuel strainer installed and with q ARROW the strainer removed Replace the fuel strainer if it is excessively contaminated or ange if the fuel flow is not smooth Eek note a mA Note the Installation direction of the fuel strainer Se sure E to install it as shown in the drawing i e with the cup facing down Fuel flaws avan though the strainer is in stalled upside down but it contaminates the inner wall of the strainer and prevents visual inspection of the srainer FUEL FLOW 3 Remove the fuel valve lock nut and check the fuel st
25. er orana justments ere within specifications i Te sot acre lo ei a s tastory preser ana shoul not be romoved ries te earacere bend fouls The screw itor cap for plug ie tactary inaral to pre vent risauntmert De hot temave te We ee pil ues the screw is being renee BLUG TYPE ONLY Cover a onening wn tame to Kean met porn out when the Bag eden i AUTO BYSTARTER SET PLATE CHOKE ARM SYNCHRONIZATION ADJUSTING SCREWS 8 18 Date of Issue Sap 1988 HONDA MOTOR CO LTD FUEL SYSTEM Using a pair of pliers break off the pilot screw ar air screw limiter cap and discard it Turn the pilot screw or air screw in and carefully count the number of tums before it seats lightly Make a note of this to use as a referenca when reinstalling the pilot screw CAUTION Tightening the pilot or damage tha seat screw against its seat will Remove the pilot or air screw and inspect it Reptace it if it is worn or damaged Plug typo Center punch the pilot screw or air scraw plug ta center the duill point Drill through the plug with a 4 mm 5 32 in drill bit Attach a drill stop to the bit 3 mm 1 8 in from the and to prevent drill ing into the pilot screw CAUTION Use extrema cara whon deiling into tho pilot for aid LL seraw to avoid damaging it Force solt tapping 4 mm screw H C 069399 P N 89903
26. fficiency is improved PRESSURE WAVE NEGATIVE PRESSURE AT EXHAUST PORT Date of Issue Sep 198 6 2 HONDA MOTOR CO LTD EXHAUST SYSTEM On 2 stroke engines thera is the possibility that the air fuel mixture that was scavenged just betore tha and of the exhaust stroke may leak aut to some degree and be discharged into the exhaust port The gas is discharged into the muffler forming a high pressure wave This pressure wave impacts against the taper at the end of the muffler rebounds and applies a positive pressure to the exhaust port The alt fuel mixture that was about to be discharged before the exhaust port clases is thus forced back ima the cylinder and the exhaust pulse scavenge effect is Improved Since the pressure wava cycle changes in accordance with the change in engine speed the exhaust pulse scavenge effect is not always as affective as it could be at all engine speeds The exhaust pulse scavenge effect is regulated to a cortain range of engine speed Therefore the exhaust system is dasignad to be most effective and mast suitable for each model depending on its intended use Note that if the exhaust system is deformed due to denting or exhaust gas leakage it can effect the exhaust pulse and result in a drop in engine horsepower COMMON EXHAUST PIPE The muffler of the conventional 4 stroke muicylinder engine uses an independent pipe for each cylinder but most recent modets
27. g to hunting during acceleration Blow apen the fuel passages in the diaphragm caver with low Pressure air AIR CUT OFF VAVLE Ramove the screws air cut off valve cover spring diaphragm and O ring Check the diaphragm for damage or pin holes Chack the O ring for damage or fatigue Awom O ring and or damaged diaphragm causes air to leak from the air cut off valve vacuum chamber Blow open air passages in the cover with compressed air CARBURETOR CLEANING Aor removing all parts blow open air and fuel passages inthe carburetor bady with compressed air CAUTION Cleaning the air and fuel passages with a piece of wira Will damage the carburetor body or fuel pump Remove the diaphragms to provent damage to tham botora using air to blow open the passages CARBURETOR ASSEMBLY AIR CUT OFF VALVE Install the diaphragm on the carburetor body Instal the O ring with its flat side pointed downward install the spring on the cover and install the cover on the car buretor body Be sure that the diaphragm and O ring do mur m terere with the cover RoD DIAPHRAGM DIAPHRAGM CARBURETOR BODY piapancom I Date of Issue Sep 1888 8 14 HONDA MOTOR CO LTO pay PROJECTIONS Align the projections on the diaphragm with the grooves in the float chamber FUEL SYSTEM ACCELERATOR PUMP install the spring on the diaphragm cover and install th
28. high altitude carburetor adjustment at tach this label at the specified location Insttuctions for obtaining the update label are given in Service Letter No 132 3 Vacuum hose routing diagram label Californis model only Route the vacuum hoses as shown on this label On after 85 models all hoses usad in the secondary air supply and evaporative emission systems are numbered far identification so compare the hose number with this label when connecting one of these hoses NOTE J Refer to the Model Specific manual for the location of each label EMISSION CONTROL SYSTEMS REED VALVE REED STOPPER REED EXAMPLE ea armenan se et a Date of Issue Sep 1988 HONDA MOTOR CO LTD 7 9 8 FUEL SYSTEM SERVICE INFORMATION 8 1 FUEL AUTO VALVE 8 8 TROUBLESHOOTING 8 2 CARBURETOR DISASSEMBLY SYSTEM DESCRIPTION gg INSPECTION 8 9 ACCELERATOR PUMP g 7 CARBURETOR ASSEMBLY 8 14 AIR CUT OFF VALVE a7 PILOT OR AIR SCREW ADJUSTMENT 8 18 REED VALVE gy ACCELERATORPUMP ADJUSTMENT 8 24 FUEL LINE aa HIGHALTITUDE ADJUSTMENT 8 24 SERVICE INFORMATION Gasoli axtramoly flammable and is explosive under certain conditions Work in a well ventilated area Smoking or allowing flames or sparks in the work area or where gasoline is stored can cause a fire or explosion CAUTION Bending or twisting the contro cables will impair smooth operation and could ca
29. just the idle speed with the throttle stop screw 11 Perform steps 8 9 and 10 for all the carburetor pilor screws 12 Install the new limiter cap or plug onto the pilot serew head nage 8 23 IOLE DROP PROCEDURE 4 stroke single carburetor emissions control applicable models NOTE The pilot screw is factory pre set and no adjustment is necessary unless the pilot screw is replaced Use a tachometer with graduations of 100 rpm or Smaller that wil accuretely indicate a 100 rom change 1 1 Turn pilot screw clockwise until it seats lightly then back it out to the specification given This is an initial setting prior to the tinal pilot scraw adjustment INITIAL OPENING Refer to the Model Specific manual CAUTION F Tight ning the pilot screw against its soat will damage the soat J 2 Warm up the engine to operating temperature Tan minutes of stop and go driving is sufficient 3 Attach a tachometer according to its manufacture instructions 4 Adjust the idle speed with the throttle stop screw IDLE SPEED later to the Model Specitie manual 5 Turn the pilot screw in or out slowly to obtain the highest engine spoed 8 Readjust the idle speed with the throttle stop screw 7 Turn the pilot screw in gradually until the engine speed drops 100 rpm 60 rpm on some models 8 Turn the pilat screw counterclockwise to the final opening from the position abtained in step 7 FINAL OPE
30. justment The pilot screws are factory pr neces S ara replaced with graduations of 50 rpm or smatter that will accurately indicata a SO rpm change 1 Turn each pilat screw clockwise unti it seats lightly then beck it out to the specification given This is an initial sor ting prior to the final pilot screw adjustment INITIAL OPENING Refer to the Mode Specific manu CAUTION 1 Tiatoning the pilot serow agains tes zoar will damage tho soat 2 Warm up the engine to operating temperature Tan minutes of stop and go driving is sufficiant S Attach a tachometer according to its manufacturer s instructions Adjust the idle speed to the specified pm with the throttle stop screw IDLE SPEED Refer to the Model Specific manual teup i Pilot screws 1 2 turn out from the initial setting f the engine spaed increases by 0 rpm or more turm all pilot screws out by successive 1 2 tum increments unti engine speed does not increase Adjust the idle speed with the throttle stop screw 5 Turn the No 1 carburetor pilot soraw in until the engine Speed drops 50 rpm ples waster sranc fj PILOT SCREW AA UNITER cap Date of Issus Sen 1988 8 20 HONDA MOTOR CO LTD 9 Tum the No 1 carburetor pilot scraw counterclockwise to he final opening from the position obtained in step 8 FINAL OPENING Refer to the Modal Specific manual 10 Ad
31. ly flood the carburetor Remove the valve Model Specific manus t if it can be removed Refer to the L Replace th ling washer Check the titer for damage or clogging Blow the fiter with low pressure air and clean it Remove the main jet needte jet hold f naedle jet and slow jet NOTE Not ali carburetors have a removable needie jet and slow Jot Refer to the Model Specific manual Turn in the pilot for air screw and record the number of turns it takas bofore it seats lightly NOTE Do not force the screw against its saat the seat wil be damaged Motoreycles with emission control system Refer to page 8 18 for pilot for sir scraw ramaval Clean the jets with cleaning solvent and if necessary blow open with compressed air f the motorcycta is equipped with an accelerator pump blow chen the fuel passages in the float chamber with fow pressure FLOAT VALVE FLOAT PIN VALVE SEAT TIP OF THE FLOAT VALVE FLOAT o VALVE SEAT FILTER THROTTLE STOP SCREW PILOT SCREW Iy SLOW JET Date ot Issus Sep 1988 8 13 HONDA MOTOR O LTD FUEL SYSTEM ACCELERATOR PUMP Remove the screws and diaphragm cover Remove the spring and diaphragm Check the rod for bends or damage Check the diaphragm for damage or pin holes Damage tothe rod and or diaphragm reduces the efficiency of the pump leadin
32. ly out of specification However be sure to check all related parts for trouble Refer to the Modet Specific manual for specified resistance Remove tha carburetor and let it cool down for 30 minutes Insert a vinyl tube into the fuel enrichening circuit and blow in to the tube Air should flow into the circuit If air does not flow into the cuit replace the auto bystarter Connect the battery to the auto bystarter terminals and wait for 5 minut Insert a vinyl tube into the fual anrichoning circuit and blow in to the tube Air should not flow into the circuit If air flows into the circuit replace the auto bystarter Check the resister if the auto bystarter is normal but engine is stil hard to start ALTERNATOR lf there is a braken wire ia the resister current will not flow to the PTC and the auto bystarter will not operate Mf there is a shorted wire in tha resister current of a higher voltage than spacified will raach the PTC This will cause the fuel enrichening circuit to close toa soon and starting will be difficult Date of Issue Sep 1988 8 10 HONDA MOTOR CO LTD FUEL SYSTEM AUTO BYSTARTER REMOVAL Remove the bystarter cover Remove the screws and set plate Remove the auto bystarter from the carburator body BYSTARTER VALVE Manual Loosen the starter valve nut and remove the valve spring and valve Check the valve fac
33. malfunction Air screw or pilot screw misadjusted Slow circuit or bystarter circuit clogged Float ievel misadjusted Fuel tank breather tube or hole clogged Air vent control valve faulty Hoses of the emission control system faulty Purge control valve faulty ing Afterburn when engine braking is used Air cut off valva malfunction Lean mixture in slow circuit Secondary air supply system faulty Hose of emission control system faulty Backfiring or misfiring during accelaration ignition system tauhy Fuel mixture 100 lean Poor performance idtiveabllity and poor fuel economy Fue system clogged Ignition maitunction Faulty air vent control valve Damaged misconnected emission control system hoses Date of Issue Sep 1988 8 2 HONDA MOTOR CO LTD FUEL SYSTEM SYSTEM DESCRIPTION CARBURETOR As the piston begins its dascent at the start of the induction phase the period when the air fuel mixture is drawn ini pressure in the cylinder drops causing air to flow from the air cleaner through the carburetor and into the cylinder The function of the carburetor is to atomize the fuel and create an air fuel mixtura As in the figures on the right air drawn into the carburetor passes through constriction A where it gains speed The con striction is known as the venturi section of the carburetor This increase in flow speed is accompanied by a fall in pressure in the ve
34. ng Diagram Label Refer to tho Modal Specific manual Refer to the Model Specific manual for emission control system application nt damage be suro to remove the diaphragms before cleaning air and fuel pascages with compressor TROUBLESHOOTING Engine stalie hard to start rough idling Purge control valve faulty Air vant controt valve faulty Hoses in the emission control system faulty Afterburn when engina braking is used Secondary air supply system faulty Hoses in emission contro system faulty Poor parformanca driveability and poor fuel economy Faulty air vent control valve Damagedimisconnected emission contro system hoses Date of issue Sep 1988 7 1 HONDA MOTOR CO LTD x EMISSION CONTROL SYSTEMS SYSTEM DESCRIPTIONS The U S Environmental Protection Agency and California Air Resources Board CARB require manufacturars to certify that their motorcycles comply with applicable exhaust emissions standards during their useful life whan operated and maintained according to the instructions provided and that motorcycles built after January 1 1983 comply with applicable noise emis sion standards for ane year or 6 000 km 3 730 miles after the time of sale to the ultimate purchaser when operated and maintained according to the instructions provided Compliance with the terms of the Distributor s Warranties for Honda Motorcycle Emission Control Systems is nacessary in order to keep
35. nturi which is used to draw off tuel from the outlet Tha fuel is atomized as it is drawn into the venturi undar the in fluance of atmospheric pressure and is mixed with the incom Ing air Carburetors ara also equippad with mechanisms for regulation of the air and mixture volumes A throttle valve is used to ragulate the flaw of air fuel mixture and a choke is included for adjusting the air flow under starting conditions Types of carburetors Carburetors which alter the diameter of the vanturi by throttle valve movement ara known as variable venturi types Honda uses this kind of carburator on its motorcycles and scootars Carburetors in which tha venturi diameter is not altered are called fixed venturi type carburetors The variable venturi con tinuously changes in diameter from tow to high speed in pro portion to the intake air volume to give smooth aspiration at low speeds and improved powar output in the high speed range Honda matarcycles scooters and ATVs use one of two variable venturi designs 1 The constant venturi type CVI the venturi diameter is altered automatically by vacuum piston that rises and falis to alter the diameter The throttle valve is installed as a separate mechanism 2 Tha piston valve or flat slide type a throttle controlled piston is used to alter the venturi diameter Principle of the vacuum piston oparatad CV type As the engine is started and the throttle valve opens the air flow in
36. rainer i screen for contamination Tighten the lock nut to the oir d torque Hpinr 1 inner watts get contaminated making visual inspection difficult FUEL AUTO VALVE SMALLER DIAPHRAGM The fuel auto valve has two diaphragms which ate intercon nected with an aluminum link LARGER DIAPHRAGM SPRING When the engine is started vacuum force is apptied to the pyc wine smaller diaphragm through the larger diaphragm and link the t fuel line opens and the fuel starts to flow Whan the engine is stoppad the diaphragms are returned to LINK their original positions by the spring and the fuel line is blocked VACUUM LINE by the small diaphragm VENT INSPECTION Keep flames and sparks away irom gasoline and wipe up spill ed gasoline at once CAUTION Ba sura to remove the diaphragms from the fuel auto valve before using comprassed alr to blow out the sir passages Compressed air will damage the diaphragms or may force them off the aluminum link Se 8 8 Date of issue Sep 1988 HONDA MOTOR CO LTD FUEL SYSTEM 1 Disconnect the fuel line and place it in clean container as shawn NOTE place clean Aana under the fool be e Refer to the Model Specific manual for replacement 2 Connect the fuel auto valve vacuum tube to the vacuum pump and apply vacuum Be sure that the fuel flows out smoothly Ht tha vacuum does not remain steady
37. rcoal canister NOTE If the PCV has two hose fittings that go ta the charcoal canister connect the blocked tube onto the other fitting to prevent air leaks TO CARBURETOR PCV OUTPUT PORT TO CANISTER CV INPUT PORT PRESSURE While applying the spacified vacuum to the PCV nose that goes to the vacuum part pump air through the canister hose Air should flow through the PCV and out the hose that goes to the carburetor Replace the PCV if air does not flow out PRESSURE PUMP ST AH 255 MC7 U S A oniy CAUTION gt Damage to the purge contral valve may result from use of a high pressure ait source Use a hand oporated pir pump only Remove tha pump install the PCV on its mount route and t the hoses according to the vacuum hose routing diagram label AIR VENT CONTROL VALVE AVCV NOTE Th ir vent control valve should be inspected if angine tart is dficuk Disconnect the AVCV hoses trom their connections and remove the AVCV from its mount Refer to the vacuum hose routing diagram label for hose connections Connect a vacuum pump to the hese that goes to the vacuum tube fitting VACUUM PUMP ST AH 260 MC7 Apply the specified vacuum to the AVCV SPECIFIED VACUUM 250 mm 9 8 in Hg The specified vacuum should be maintained Replace the AVCV if vacuum is not maintained TO VACUUM PORT vacum PUMP roa PUMP Date of Iss
38. tages Staga 1 2 3 etc counted from the top The clip position staga number in creases with an incraase in the degres of throttle opening raising the cross sectional area of fuel passage and hence the volume of tuel Size of the main jet does not affect the air fuel mixture ratio at this stage as the fuel flow at main jet is greater than st the neadle jet JET NEEDLE Main systom fully opan With a degres of thrattie opening of 1 2 fully open the ven turi bore diameter and mass flow af ait become maximum At this time the volume of fuei drawn from the gap between the needle jet and jet needle becomes too great end exceeds tha flow volume of the main jet Five ls regulated j at this point When the clearance between the needle jet and jet needle is too great the fuel flow is regulated by the main jet to prevent an overly rich fuel sir mixture MAIN JET Date of Issue Sep 1988 8 6 HONDA MOTOR CO LTD FUEL SYSTEM ACCELERATOR PUMP When the throttle valve is opanad suddenly air fuel mixture drawn into the oylinder momentarily becomes lean Because the vacuum at the venturi drops air flow at the venturi slows down and the drawn up fuel becomes toa little compared with the air To avoid thinning of the mixture under these condi tions an accelerator pump is used for temporary enrichment The principle of operation of the pump is as follows As tha throttle valve is opened
39. tha air vent control valve is open and air is drawn into the carburetor through the valve CARBURETORS PURGE CONTROL DI CHARCOAL CANISTER AIR VENT CONTROL VALVE AIR VENT CONTROL VALVE KI IAT ENGINE STOPI TO OPEN AR lt FRESH AIR FUEL VAPOR NOISE EMISSION CONTROL SYSTEM TAMPERING WITH THE NOISE CONTROL SYSTEM IS PROHIBITED Foderal law prohibits the following acts or the causing thereof 1 Tha ramoval or rendering inoperative by any person other than far purposes of maintenance repait ot replace ment of any devica or element of design incorporated into any new vehicle for the purpose of noise control prior to its sale or delivery to the ultimate purchaser or while itis in use or 2 the use of the vehicle after such device or element of design has been ramaved or rendered inaparative by any person AMONG THOSE ACTS PRESUMED TO CONSTITUTE TAMPEHING ARE THE ACTS LISTED BELOW 1 Removal af or puncturing the muffler bafflas header pipes ar any other component which conducts exhaust gases 2 Removal of or puncturing of any part of the intake system Lack of proper maintenance gt Replacing any moving parts of the vehicle or parts of the exhaust or intake system with parts other than those specified by the manufacturer tn ne ge 7 Date of tesue Sep 1988 4 HONDA MOTOR CO LTD EMISSION CONTROL SYSTEMS SYSTEM INSPECTIONS EVAPORAT
40. tha main bore exerts a strong negative pressure on the dower section of the vacuum piston see Carburetor theory At this point air is drawn out of the carburetor s vacuum chamber and pressura in the chamber drops The diaphragm is lifted due to atmospheric pressure and the vacuum piston is raised When the throttle valve is closed sis flow in tha main bore is obstructed Pressure returns to that of the atmosphare and the vacuum piston is lowated by spring force VENTURI ATMOSPHERIC __ pleaessune BY Large dr p in pressure Small drop in pressure A FLOW SS THROTTLE VALVE c ATMOSPHERIC PRESSURE CV TYPE VACUUM PISTON 5 THROTTLE vacuum DIAPHRAGM SPRING PRESSURE AIR FLOW M Date of Issue Sep 1988 HONDA MOTOR CO LTO FUEL SYSTEM Operation of systems The carburetor is comprised of a starting system which uses either a choka valve of bystarter valve a float system for fuel MAIN JET supply and slow and main jet systems etc JET NEEDLE Clip position The tuel supply system varies with the degree of throttle open aR ing and regulates fuel according to a slow system at low throt tle openings throttle opening fully closed to 1 4 openh At lt gt JET NEEDLE Straight section medium throttle openings opening 1 8 3 4 the main system s jet needle is used to regulate the fuel The straight SLOW JET and AIR SCREW
41. the emissions system warranty in effect SOURCE OF EMISSIONS The combustion process produces carbon monoxide and hydrocarbons Control of hydrocarbons is very important because undar certain conditions they react to form photochemical smog when subjected to sunlight Carbon monoxide does not react in the same way but It is toxic Honda Mator Co Ltd utilized lean carburetor settings as well as other systems to reduce carbon monoxide and hydrocarbons CRANKCASE EMISSION CONTROL SYSTEM The crankcase emission control system routes crankcase emissions through the air clesner and into the combustion chamber Condensed crankcase vapors are accumulated in an air oll saparator and drain tube which must be emptied periodically Refer to the Maintenance Schedule for each model The drain tube needs to be checked for oil accumulation more frequently if tha machine has been consistantly ridden at high speeds or in rain AIR CLEANER AIR OIL SEPARATOR TRANSPARENT SECTION DRAIN TUBE DRAIN PLUG lt FRESH AIR BLOw BY GAS 2 Date of Issue Sep 1988 7 HONDA MOTOR CO LTO EMISSION CONTROL SYSTEMS EXHAUST EMISSION CONTROL SYSTEM SECONDARY AIR SUPPLY SYSTEM The exhaust emission camtrol system is composed af lean carburetor settings and no adjustment shouid be made except idie speed adjustment with the thrattie stop screw The exhaust emission control system consists of a secondary air supply s
42. ue Sep 1988 HONDA MOTOR CO LTD EMISSION CONTROL SYSTEMS Connect the vacuum pump to the air vant fitting on the AVCV that goes to open sir NOTE Ifthe AVCV has two hose fittings that go to open air connect the blocked tube onto the other fitting to pre vent air leaks Apply vacuum to the AVCV The vacuum should hold steady Replace the AVCV if vacuum leaks Connect the vacuum pump to the hose that goes to the vacuum tube fitting VACUUM PUMP ST AH 260 MC7 U S A only Connect the pressure pump to the air vent fitting an the AVCV that goes to opan air PRESSURE PUMP ST AH 255 MC7 U 8 A oniy Nove pad 1 VALVE AIR VENT PORT QA P PUMP TO VACUUM PORT AIR VENT PORT PRESSURE PUMP The AVGW fae twa hose Wings at B 1 open Sk Connect the blocked tube onto the ether tmine to pe vent air leaks i White applying the vacuum to the AVCV hose that goes to the vacuum tuba fitting pump air through the air vent fitting Air should flow through the AVCV and out the hose that goas to the carburetor CAUTION Damage to the air vent control valve may result from use at a high pressure air source Use a hand operated air Pump only Plug the hose that goes to the carburetor NOTE If the AVG has two hose fittings that go to open connect the blocked tube onto the other fitting to
43. use the cables to stick or bind resulting in loss of vahicle control Be sure to remove the diaphragms bafore cleaning ait and fuel paszages with compri imaged sed vir Tha diaphragms might be Refor to Madel Specific manual tor carburetor and reed vatve removal instalation When disassembling tuel system parts note the locations of the O rings Replace them with new onas on reasyembly Before disassembling the carburetor place a suitable container under the carburetor drain bolt loosan the bolt and drain the carburetor After removing the carburetor wrap the intake port of the engine with a shop towel or cover it with piece of rupe to pre vent any foreign material from dropping into the engine NOTE If vehicle is to be stored for more than one month drain the float bowls Fuel left in the float bowls may cause clogged jots resulting in hard starting or poor driveability FUEL FRESHNESS AND TROUBLESHOOTING Engine performance is directly related to the quality and freshnass of the gasoline consumed Therefore it is important to be sure the fuel within the motorcycle scooter or ATV you ara servicing is usable for your testing procedures You may save valuable troubleshooting time by replacing fuel if its quality or age is in doubt Detonation or pinging on acceleration is an indication that the fuel is either not of good quality or is tao iow in actane rating for your application Fuel should
44. ust the idle speed with the throttle stop screw 9 Install the limiter cap for plug on to the air or pilot screw paye 8 23 AIR SCREW ADJUSTMENT 2 stroke engine oniy Warm the engine up to operating temperature Tur the air scraw clockwise until it seats lightly then back it Out to the specification given AIR SCREW OPENING Refar to the Model Specific manual CAUTION Tghnie he serow agairt ila sat wt domage hae J Date of Issue Sep 1988 8 22 HONDA MOTOR CO LTD FUEL SYSTEM Adjust the idie speed with the throttle stop screw IDLE SPEED Refer to the Model Specific manual Rev the engine up slightly from the idle speed and make sure that engine speed rises and returns smoothly Adjust by turing the air screw in or out within a 1 4 turn if necessary If the engine cannot be adjusted by turning the air screw within a 1 4 turn check for ather engine problems LIMITER CAP OR PLUG INSTALLATION LIMITER CAP If the pilot screw for air screw is removed a new limiter cap must be installed after the screw is adjuster After adjustment coment the limiter caps over the screws us ing LOCTITE 601 or equivalent The limiter cap should be Placed against its stop as shown praventing further adjust ment that would enrich the fuel mixture Pilot screw the limiter cap position permits clockwise rotation and prevents counterclockwise rotation gt
45. while prassing it in and remave it Ramove the spring spring holder jat needle needle holder and washer from the vacuum piston NOTE _Certain models are not quipped with a spring holder J Check the jet needle tor stepped wear and replace i necessary Check the vacuum piston for damage and replace if necessary Check the diaphragm for damage pin holes wrinkles and bends and replace if necessary Air leaks out at the vacuum chamber if the diaphragm is damaged in any way even a pin hole JET NEEDLE ET NEEDLE SPRING NEEDLE CUP RETAINER VACUUM CHAMBER COVER SPRING ACUUM PISTON Bi VACUUM PISTON ASSEMBLY JET NEEDLE HOLDER VACUUM PISTON DIAPHRAGM SPRING HOLDER JET NEEDLE HOLDER O JET NEEDLE SPRING Date of Issue Sep 1988 8 12 HONDA MOTOR CO LTD FUEL SYSTEM FLOAT JETS FLOAT Remove tha fost chamber Ramove the float pin float and float valve Check the Iaat for damage If it is a hollow float type aiso check it for deformation and fuel in the float Check the float valve and valve soat for scores scratches clogging and damage Replace if necessary Gheck the tip of the float valve where it contacts the valve Seat for stoppad wear or contamination Replace the fowt valve if its tip la wom or contaminated A worn or con fiaainated valve does not seat properly and will eventual
46. ystem which introduces filtered air into the exhaust gases in the exhaust port Fresh air is drawn into the exhaust port whenever there is a negative pressure pulse in the exhaust system This charge of fresh air promotes burning of the unburned exhaust gases and changes a considerable amount of hydrocarbons and carbon monoxide into relatively harmless carbon dioxide and water A reed valve prevents reverse air flaw through the system The air injection contral valve reacts to high intake manifold vacuum and will cut off the supply of fresh air during engine deceleration thereby preventing afterburn in the exhaust system No adjustments to the secondary air supply system shouid be made although periodic inspection ot the components is recommended AIR INJECTION VACUUM TUBE CONTROL VALVE AIR CLEANER REED VALVE Date of Issue Sep 1988 HONDA MOTOR CO LTD 7 3 EMISSION CONTROL SYSTEMS EVAPORATIVE EMISSION CONTROL SYSTEM California model only All Handa motorcycles and scooters sold in California for street use comply with the California Air Resources Board re quiraments for evaporative emission regulations Fuel vapor from the fuel tank and carburetors is couted into the charcoal canister where it is absorbed and stored while the engine is stopped When the engine is running and the purge contro diaphragm valve is open fuel vapur m the charcos canister is drawn into the engine through the carburetor At the same time

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