4. Fuel System

f'G?\HONDA NUSO· NUSOM 4. FUEL SYSTEM

4-1 FLOAT LEVEL INSPECTION 4-5 TROUBLESHOOTING 4-1 CARBURETOR INSTALLATION 4-6 I THROTTLE VALVE DISASSEMBLY 4-2 THROTTLE VALVE INSTALLATION 4-6 I CARBURETOR REMOVAL 4-3 REED VALVE 4-8 i FLOAT/FLOAT VALVE/JETS 4-3 FUEL FILTER AND TANK 4-9 DISASSEMBLY 10I JETS/FLOAT VALVE/FLOAT 4-5 I ASSEMBLY I SERVICE INFORMATION GENERAL

ciJution when working with gasoline. Always work in il well·ventilated area ;Jnd 'lway from sparks or fjarnes. VVhen disassemblmg fuel system parts, nOtC the locations of the a·rings. Replace them with new oncs during assembly. Bleed air from the OJI outlet line whenever it is disconnected.

5PECIFICATlONS _ L:,enlUri __ r__ I' ! Identifrcation number r, PA13E I Float 12.2 ± 1.0 mm (0,48 -! 0.04 in) ! Ail' screw opening 2 turns Qut lelle spl1ed 1.800 ± 150 rpm I Throllie grip free play 2-6 mm 1118-1/4 in)

TOOL

Floin level Gauge 0740 I 10000

TROUBLESHOOTING

Engine cranks but won'! start lean mixture 1, No fuel in lank 1. Carburetor fuel jets clogged 2, Clogged lube 2. Fuel Cilp vent clogg\!d 3. Clog(Jcd fllcl stri!!rW! 3. Clogged fuel filter 1. Too much fuel getting to cylinfJer 4. Fuel line kinked (}r restricted 5. CI09!/cd ail' cleaner 5. Float valve faulty 6. F(lulty control box 6. Float level tOO low 7. Air lIent tuhe clogged

Engine Idles IO(l9hly, Of' runs poorly Rich 1. Idle speed incorrect 1. Faulty float vallie 2 Rtch t1)tXtllHl 2. Float level 100 high 3. Lean mixture 3. Carburetor air iets closs 4. Clogged air cleaner 5. Inlet pipe leilking (:i. Fltcl contaminated

Daw of Issue: Nov.. 1981 35 ID HONDA MOTOR CO., lTD. 4-1 FUEL SYSTEM NUSO·NUSOM

CARBURETOR CAP THROTTLE VALVE DISASSEMBLY

Remove the battery and battery holder.

Remove the carburetor cap and pull out the throttle valve. •

THROTTLE VALVE SPRING DIsconneCt the thran1e cable from the throttle valve. Remove Ihe throttle valve spring. cap and thronle valve.

THROTTLE CABLE THROTTl VALVE

Pry off the needle teta,"er and remove the jet needle.

RETAINER JET NEEOLE/THROTILE VALVE INSPECTION SECOND NOTCH I$TOI Check the jel needle and throttle valve for wear or damage. JET NEEDLE

ru"On" """' -[J

36 Date of Issue: NOli., 1981 4-2 © HONDA MOTOR CO.. lTD 0\HONDA NU50· NU50M FUEL SYSTEM

BYSTARTER TUBE FUEL LINE BYSTARTER TUBE CARBURETOR REMOVAL I Turn the fuel vallie OF F and disconnect the fuel line, air venl tube, hvstarter tubes and oil out leI line trom lhe carburetor.

Remove the carburetor attaching nulS.

AIR VENT OIL DUTLET CARBURETOR TUBE LINE ATIACHING NUTS

AIR CLEANER Remove the holts attaching Ihe rear fender. 'L..-// 7" Relnove the ail cleaner bracket atlaching boilS and the air cleaner with bracket. Remove :he carburelOr and disconnect Ihe dram tube 'rom 11.

BOLTS MOUNTING BRACKET

FLOAT /FLOAT VALVE/ JETS OISASSEMBLY Place a drain pan under the carburelOr and loosen the carburetor dlain screw to allow tuel 10 drain in the drain pan. Remove the float chamber from the carbu,elor body_

Oil,e 01 lnut: Nov., 1981 31 EO HONDA MOTOR CO., lTD. 4-3 HONDA FUEL SYSTEM NU50·NU50M

Remove the carburetor float and lIoat valve by removing the attaching screw.

Remove the float pin.

FLOAT/FLOAT VALVE INSPECTION VALVE SEAT Check the valve seat for wear or damage. Check Ihe float for deformation or fuel inside the float. -""

AlA 5 REW Remove the air screw, record the number of rotations until it seats lighllv, so it can be returned to the orlgimll position. ----, /){J 1101 force the screw agaillst its seQr 10 damage.

38 Date of Issue; NOli., 1981 4-4 ©HONDA MOTOR CO.. LTD. QHONDA

NU50·NU50M FUEL SYSTEM

Blow open aU lets and body openings with com- j)(essed air.

AIR GUN

JETS /FLOAT VALVE/FLOAT FLOAT ...... --FLOAT ASSEMBLY SCREloV

Install the air screw and throttle stop screw.

AIR SCREW OPENING: 2 turnSQut

Install the float valve, float and float pin. Tighten the floal screw securely.

THROTTLE STOP SCREW AIR SCREW

FLOAT LEVEL INSPECTION

Measure the ftoat level at the main jet parallel with the float oin.

FLOAT lEVEL: 12.2.t 1.0 mm {O.48;t 0.04 inl

Replace Ihe float II It IS Qut of the specified level lange. Check the operation of the float and install the float chamber.

\ FLOAT LEVEL GAUGE

Dale of Issue. Nov., 1981 39 e HONDA MOTOR CO .• LTD. 4-5 FUEL SYSTEM NUSO· NUSOM

FENDER ATTACHING BOLT CARBURETOR INSTALLATION CAUTION:

f)o 1101 allow foreign parlicles 1(1 f!.lIler Ihe carburelOr.

Connect the carburetor drain tube and install the carburetoL

NOTE ! Do not forget to install the 0·rin9.

Install the air cleaner with bracket. Install the rear fender to the air cleaner mounting bracker. BolIS MOUNTING BRACKET

BYSTAATER TUBE BYSTAfHER TUBE. Connect the tubes and line to the carburetor.

AI R VENT TUBE OIL OUTLET TUBE

THROTTLE VALVE INSTALLAnON Install the jet needle on the throttle valve and secure with the needle clip...... NEEDLE CLIP

-----RETAINER LEAN JET NEEDLE { 1 1st

{STO} " 2nd NOTCH : THROTTLE VALVE i RICH.. NOTCH 1U,

40 Date of Issue: Nov., 1981 4-6 ©HONDA MOTOR CO., LTD NU50· NU50M FUEL SYSTEM

Assemble the rubber carburelOr cap and thrOllle RUBBER SEAL lIill\'(' spring. ,

CARBURETOR CAP

/' THROTTLE VALVE SPRIN

Connect the throttle cable \0 the throttle ...

THROTTLE CABLE THp....TTl VALVE

CAP Slide the throttle valve imo lhe carburetor body,

NOTE ----, Align the groove in the valve with the throule SlOp screw on the carburetor body.

Tighten the carburetor cap. Perform the following adjustments and operation: Throttle cable free play adjustment (Page 3·51 Oil pump control cable adjustment lPage 3·61 011 pump and line bleeding {Page 2·71 Idle soeed :Jdiustment (Page 3·61.

GROOVE

Date of Issue: No..... 1981 CD HONDA MOTOA CO., lTD. 4-7 FUEL SYSTEM NUSO·NU50M

BYSTAATER TUBE REED VALVE REED VALVE REMOVAL

Remove the carburetor (Page 4·3).

Oisconnect the bystarter lube from the intake pipe. Remove the intake pipe and reed valve.

INTAKE PIPE REED VALVE

REED VALVE INSPECTION Check the reed '1alve for damaged or weak reeds. Check the valve seat for cracks, damage or clearance between Ihe seal and reed. Replace the valve if necessary.

CAUTION: Do /lOt disassemble or bend the reed stopper. To do so can cause loss of power and t'ngine damage. If the sropper, reed or valve sear i.f faulty, replace them as a unit.

REED VALVE SEAT

BYSTARTER TUBE REED VALVE INSTALLATION The installation sequence is essentially the reverse of removal. Connect the bystarter lube to the intake pipe. After installation. check for leaks.

FUEL FILTER AN 0 TANK

/fl FUEL STRAINER-=--a

FUELVALVE lt

<- ..... 0 FUELFILTEA @

MOUNTING NUT 131

LOCK NUT FUEL STRAINER CLEANING

With ,f,e fuel valve OFF, disconnect the fuel line.

Kci.'p 011'0)' from flames Of sparks. Wipe lip spilled gasoline at once.

Turn lhe fuel valve ON and drain the gasoline into a safe container labeled for g8soline.

Droi" the gasoline illfO a safe cOfltaint:f labeled for gowlint.'.

Remove the lock nut and remove the fuel valve.

Remove the fuel filter. Clean the filter with compressed air. Remove and clean the fuel filter fpage 3·31. Assemble and reinstall the fuel valve.

CAUTION'

Do /Jot forget 10 il/sIIlll tfu: O-ril/g. I ___-.1 NOTE After assernbling, check for ICilks. . 00 not overtighten the lock nul. -0

BGCI-15

FUEL TANK REMOVAL S'1"I.l-lIII ilfj };"ep gasoline away from flames or sparks. llIipc Ufl spilled gasolint' at O/lce. rf)raill lhe gUSolilH'-;nlO a mie coma;lIef [ for Sliw/inc. , , Remove the fuel valve {page d-lOL Remove the fuel tank mounting nuts and plain washers.

Raise the seat, seat bridge and shroud. Remove the fuel lank. MOUNTING NUTS AND PLAIN WASHERS FUEL TANK INSTALLATION SEAT BRIDGE The installation is the reverse of lemQlfa!.

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