f'G?\HONDANUSO· NUSOM 4. FUEL SYSTEM

TROUBLESHOOTING

THROTTLE VALVE DISASSEMBLY

CARBURETOR REMOVAL

FLOAT/FLOAT VALVE/JETSDISASSEMBLY

JETS/FLOAT VALVE/FLOATASSEMBLY

4-1 FLOAT LEVEL INSPECTION 4-54-1 CARBURETOR INSTALLATION 4-6 I4-2 THROTTLE VALVE INSTALLATION 4-6 I4-3 REED VALVE 4-8 i4-3 FUEL FILTER AND TANK 4-9 10I4-5 I

ISERVICE INFORMATIONGENERAL

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 PA13EI Float

,

12.2 ± 1.0 mm (0,48 -! 0.04 in)! Ail' screw opening 2 turns Qut

lelle spl1ed 1.800 ± 150 rpmI Throllie grip free play 2-6 mm 1118-1/4 in)

TOOL

Floin level Gauge 0740 I 10000

TROUBLESHOOTINGEngine cranks but won'! start1, No fuel in lank2, Clogged lube3. Clog(Jcd fllcl stri!!rW!

1. Too much fuel getting to cylinfJer5. CI09!/cd ail' cleaner6. F(lulty control box

lean mixture1. Carburetor fuel jets clogged2. Fuel Cilp vent clogg\!d3. Clogged fuel filter4. Fuel line kinked (}r restricted5. Float valve faulty6. Float level tOO low7. Air lIent tuhe clogged

Engine Idles IO(l9hly, Of' runs poorly1. Idle speed incorrect2 Rtch t1)tXtllHl3. Lean mixture4. Clogged air cleaner5. Inlet pipe leilking(:i. Fltcl contaminated

Rich1. Faulty float vallie2. Float level 100 high3. Carburetor air iets closs

Daw of Issue: Nov.. 1981ID HONDA MOTOR CO., lTD.

35 4-1

•

FUEL SYSTEM

THROTTLE VALVE DISASSEMBLYRemove the battery and battery holder.

Remove the carburetor cap and pull out the throttlevalve.

DIsconneCt the thran1e cable from the throttle valve.Remove Ihe throttle valve spring. cap andthronle valve.

NUSO·NUSOM

CARBURETOR CAP

THROTTLE VALVE SPRING

THROTTLE CABLE THROTTl VALVE

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

JET NEEOLE/THROTILE VALVEINSPECTION

Check the jel needle and throttle valve for wear ordamage.

RETAINER

SECOND NOTCH I$TOI

JET NEEDLE

ru"On" """'-[J4-2 36 Date of Issue: NOli., 1981

© HONDA MOTOR CO.. lTD

0\HONDANU50· NU50M

CARBURETOR REMOVALTurn the fuel vallie OF F and disconnect the fuel line,air venl tube, hvstarter tubes and oil out leI line tromlhe carburetor.

Remove the carburetor attaching nulS.

BYSTARTER TUBE

AIR VENTTUBE

FUEL LINE

OIL DUTLETLINE

FUEL SYSTEM

BYSTARTER TUBE

I

CARBURETORATIACHING NUTS

Remove the holts attaching Ihe rear fender.Relnove the ail cleaner bracket atlaching boilS andthe air cleaner with bracket.Remove :he carburelOr and disconnect Ihe dram tube'rom 11.

AIR CLEANER'L..-// 7"

BOLTS MOUNTINGBRACKET

FLOAT /FLOAT VALVE/ JETSOISASSEMBLYPlace a drain pan under the carburelOr and loosen thecarburetor dlain screw to allow tuel 10 drain in thedrain pan.Remove the float chamber from the carbu,elor body_

Oil,e 01 lnut: Nov., 1981EO HONDA MOTOR CO., lTD.

31 4-3

FUEL SYSTEM

HONDANU50·NU50M

Remove the carburetor float and lIoat valve byremoving the attaching screw.

Remove the float pin.

FLOAT/FLOAT VALVE INSPECTION

Check the valve seat for wear or damage.Check Ihe float for deformation or fuel inside thefloat.

Remove the air screw, record the number of rotationsuntil it seats lighllv, so it can be returned to theorlgimll position.

----,/){J 1101 force the screw agaillst its seQr 10

damage.

VALVE SEAT

-""

AlA 5 REW

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

QHONDANU50·NU50M

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

FUEL SYSTEM

AIR GUN

JETS /FLOAT VALVE/FLOATASSEMBLYInstall 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.

FLOAT LEVEL INSPECTION

Measure the ftoat level at the main jet parallel withthe 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 levellange.Check the operation of the float and install the floatchamber.

Dale of Issue. Nov., 1981e HONDA MOTOR CO.• LTD.

FLOAT ........

THROTTLE STOPSCREW

39

..--FLOATSCREloV

AIR SCREW

\FLOAT LEVELGAUGE

4-5

FUEL SYSTEM

CARBURETOR INSTALLATIONCAUTION:f)o 1101 allow foreign parlicles 1(1 f!.lIler IhecarburelOr.

Connect the carburetor drain tube and install thecarburetoL

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

Install the air cleaner with bracket.Install the rear fender to the air cleaner mountingbracker.

NUSO· NUSOMFENDERATTACHING BOLT

BolIS MOUNTINGBRACKET

Connect the tubes and line to the carburetor.BYSTAATER TUBE

AI R VENT TUBE

BYSTAfHER TUBE.

OIL OUTLET TUBE

THROTTLE VALVE INSTALLAnONInstall the jet needle on the throttle valve and securewith the needle clip. ........ NEEDLE CLIP

{

-----RETAINER

LEANJET NEEDLE 1 1st

1U{STO}

" 2nd NOTCH: ..

THROTTLE VALVE i RICHNOTCH,

4-6 40 Date of Issue: Nov., 1981©HONDA MOTOR CO., LTD

NU50· NU50M

Assemble the rubber carburelOr cap and thrOlllelIill\'(' spring.

RUBBER SEAL,

CARBURETORCAP

/'THROTTLEVALVE SPRIN

FUEL SYSTEM

Connect the throttle cable \0 the throttle ...

Slide the throttle valve imo lhe carburetor body,

NOTE ----,

Align the groove in the valve with the throuleSlOp screw on the carburetor body.

Tighten the carburetor cap.Perform the following adjustments and operation:Throttle cable free play adjustment (Page 3·51Oil pump control cable adjustment lPage 3·61011 pump and line bleeding {Page 2·71Idle soeed :Jdiustment (Page 3·61.

Date of Issue: No..... 1981CD HONDA MOTOA CO., lTD.

THROTTLE CABLE

CAP

GROOVE

THp....TTl VALVE

4-7

FUEL SYSTEM

REED VALVEREED VALVE REMOVAL

Remove the carburetor (Page 4·3).

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

NUSO·NU50M

BYSTAATER TUBE

INTAKE PIPE REED VALVE

REED VALVE INSPECTIONCheck the reed '1alve for damaged or weak reeds.Check the valve seat for cracks, damage or clearancebetween Ihe seal and reed. Replace the valve ifnecessary.

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

REED VALVE INSTALLATION

The installation sequence is essentially the reverseof removal.Connect the bystarter lube to the intake pipe.After installation. check for leaks.

REED VALVE SEAT

BYSTARTER TUBE

4-8 '2 Date of Issue: NOli., 1981© HONDA MOTOR CO.. l TO

NU50·NU50M

FUEL FILTER AN 0 TANK

/flFUEL STRAINER-=--a

o

FUELVALVE lt

<-..... 0

FUELFILTEA @

FUEL STRAINER CLEANING

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

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

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

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

Remove the lock nut and remove the fuel valve.

Date oi Issue: Nov.. 1981© HONDA MOTOR CO., LTD.

43

LOCK NUT

FUEL SYSTEM

MOUNTING NUT 131

4-9

FUEL SYSTEM

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'I Do /Jot forget 10 il/sIIlll tfu: O-ril/g.___-.1NOTE

After assernbling, check for ICilks.. 00 not overtighten the lock nul.

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-lOLRemove the fuel tank mounting nuts and plainwashers.

Raise the seat, seat bridge and shroud.Remove the fuel lank.

FUEL TANK INSTALLATION

The installation is the reverse of lemQlfa!.

4-10

BGCI-15

4-1

NU50· NU50M

-0

MOUNTING NUTS ANDPLAIN WASHERS

SEAT BRIDGE

Dale of Issue: Nov., 1981© HONDA MOTOR CO.. lTD.

ENGINE REMOVAL/INSTALLATION

\\

5-0 46 Date of Issue: Nov., 198\© HONDA MOTOR CO., lTD.