38
[J DEPARTMENT OF THE ARMY TECHNICAL MANUAL DEPARTMENT OF THE AIR lfinl Wo1d7[S(fU(fUfA\d1 FORCE TECHNICAL ORDER U lJlJ UQU -U FORMERLY TM 9-18268 CARBURETORS (STROMBERG)

Carburetor Stromberg B

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Page 1: Carburetor Stromberg B

[J

DEPARTMENT OF THE ARMY lJ~ ®Qrn®~~ TECHNICAL MANUAL

DEPARTMENT OF THE AIR lfinl Wo1d7[S(fU(fUfA\d1 FORCE TECHNICAL ORDER U lJlJ UQU -U Cilll0l0~-U

FORMERLY TM 9-18268

CARBURETORS

(STROMBERG)

Page 2: Carburetor Stromberg B

Figure 195. Model NA-Y5G carburetor.

air horn. The theory of carburetion, as explained in paragraph 13, applies to these .units. The schematic drawings in figures 196, 197, 198, and 199 illustrate the operation of the idle, main metering, power, and accelerating systems. -

c. Each barrel is equipped with a degasser assembly that auto­matically cuts off fuel to the idle system during periods of high mani­fold vacuum. An electric control provides for positive shut-off of fuel when the vehicle operator stops the engine. Figures 17, 18, and 19 show the positions of the degasser parts during idle, decelera­tion and shut-off operations. Refer to paragraph 14i for detailed description of degasser operation.

d. Figure 200 shows the N A-Y5G3 carburetor completely dis­assembled.

1'17. -Differences Between Models

Model NA-Y5G and NA-Y5G3 carburetors are of the same general design. Some of the jets differ in size and the accelerating pump of the Model N A-Y5G3 carburetor has greater capacity than that of the Model NA-Y5G. The idle needle valves in the Model NA-Y5G3 are more easily accessible than those on the NA-Y5G, employing a flexible shaft. Refer to figures 194 and 195.

Note. On the Model N A-Y5G3, the accelerating pump push rod link is attached to the throttle lever while on the Model N A-Y5G, the link is attached to a pump lever. located on the opposite end of the throttle valve plate shaft.

236

Page 3: Carburetor Stromberg B

13, .97, rer,

to­ni-of

l8, 'a­ed

s-

~1

f f

IDLE DISCHARGE JETS RA PD 183762

Figure 196. Float and idle system.

RA PD 183763

Figure 1.97 . Main metering system.

237

Page 4: Carburetor Stromberg B

RA PO 334~10

Figure 198. Power system.

DISCHARGE JET

RA PO 183764

Figure 199. Accelerating system.

238

Page 5: Carburetor Stromberg B

~ W ..0

Table XIII . Stromberg Carburetors, Models NA-Y5G and NA-Y5GS

INTER NAL SP ECIF ICATIONS

Carburetor model NA-Y5G NA-Y5G3 NA-Y5G3 NA-Y5G3

Part number__ _ _ _ ___ _ __ __ _ _ _ _ ____ ___ __ _ BX-380107 ___ ___ BX-380260 ____ _ BX-380307 ___ __ BX-380316 _____ Repair kit number ______________________ BX-383300 _____ BX-38549L ___ _ B X -385755 _____ BX-38549L ____ VenturL ______________________________ .:- 1 % in _ _ _ _ _ _ _ _ _ _ 12%2 in ________ _ 112 in __________ 12%2in _________ Main discharge jet (US STD) & ___________ 44 ____________________________ _ 70 _____________ 70 _____________ High-speed bleed (US STD) & _____ -' ______ 70 _____________ 65 ____________ _ 53 _____________ 65 ________ _____ M8in metering jet (US STD) & _____ -______ 46 _____________ 43.5 __________ _ 50 _____________ 43.5 __________ _ Power bypass jeL ______________________ 0.080 in ________ 0.096 in _______ _ 0.089 in __ ___ ___ 0.096 in ________ Idle discharge holes (US STD) & _ _ _ _ _ _ _ _ _ _ 54-53_ _ _ _ _ _ _ _ _ _ 54-56-64 ______ _ 48-54-62 _______ 54-56-64 _______ Float needle valve seat __________________ 0.180 in ________ 0.180 in _____ . __ _ 0.180 in ________ 0.180 in _______ _ Idle bleed (US STD) & ___________________ 70-48 __________ 70 __ __________ _ 6~70 __________ 6~70 __________ Accelerating pump discharge jet (US STD) &_ 58__ __ __ ____ _ _ _ 50 ____________ _ 50 _______ ~ ___ __ 50 ________ __ ___ Throttle valve plate hole (US STD) & _____ 46 _____________ 50 _________ ___ _ 50 _____________ 50 _____________ Fuel leveL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ % in. at 5 psL _ _ % in. 8t 5 psL __ % in. at 5 psL __ % in. at 5 psL __ Accelerating pump capacity ______________ 8~95 cc's b _____ 14~165 cc's b __ _ 14~165 cc's b ___ 145-165 cc's b ___

• us STD drill sizes. b cc's per 10 strokes; maximum pump travel.

o z

NA-Y5G3

BX-380317 BX-385755. 1% in. 70. 53. 50. 0.089 in. 48-54-62. 0.180 in. 6~70.

50. 50. % in. at 5 psi. 14~165 CC'S.b

Page 6: Carburetor Stromberg B

On the Model NA-Y5G3 the slow idle adjusting screw is mounted so that it is more easily accessible than the slow idle adjusting screw on the throttle lever of the Model NA-Y5G. The air horn on Model N A-Y5G3 has two vents for venting the crankcase, starter, and ignition. Refer to figures 194 and 218.

138. Data

a. Identification. All identification data, such as model number and serial numbers, are stamped on the identification plate (figs. 194 and 195) on the air horn.

b. Specifications. Table XIII lists internal specifications and other data pertinent to the Models N A- Y5G and N A-Y5G3 carburetors covered in this chapter.

Figure 200. Model NA-Y5G3 carburetor-complete exploded view.

240

A-Mail B-Acool C-Accel

SC1 D -Acce

SCI E -Acce F-Acce G-Pow H -Left J-Air l

K-VaCl L-Air : M-Air : N-Mai p-Mai Q-Rigl R-Acci S-Acc T-Acc U-Acc V-Arc

L W-Acc

1'\ X-Ace Y-Ac(

. 8 Z-AcI

~

AA-Ao E

BB-De CC-DE DD-DE EE-DE FF-Id: GG- Id HH-Id

JJ-Fl KK-Fl LL- M

MM-M NN-'r: PP-T QQ-T I.R-T 8S-P

TT-Ie UU-I( VV-F

WW-F XX-F YY-F ZZ-F AB-I!

Page 7: Carburetor Stromberg B

nted so ,rew on M odel r, and

umber rs, 194

other r etors

A-Main Body Gasket B-AccelE'rnt:ng Pump Stem and Piston Assembly C-Accelerating Pump PistoIl Stem Fulcrum

Screw D-Accelerating Pump Piston Stem Fulcrum

Screw Lock Washer E-Accelerating Pump Piston Spring F-Accelerating Pump Piston Spring Washer G-Power Vacuum Piston Assembly H-Left Venturi J-AirHorn

K-Vacuum Channel Plug L-Air Horn Screw

M-Air Horn Screw Lock Washer N-Main Body Stud Safety Nut P-Main Body Stud Washer Q-Right Venturi R-Accelerating Pump Discharge Jet S-Accelerating Pump Lever T-Accelerating Pump Lever Needle Bearing U-Accelerating Pump Lever Torsion Spring V-Accelerating Pump Lever Fulcrum Screw

Lock Washer W-Accelerating Pump Lever Fulcrum Screw

Nut X-Accelerating Pump Lever Fulcrum Screw Y-Accelerating Pump Piston Stem Fulcrum

, Screw Nut Cotter Pin Z-Accele'rating Pump Piston Stem Fulcrum

Screw Nut AA-Accelerating Pump Piston Anti-Vibration

Spring BB-Degasser Assembly CC-Degasser Gasket DD-Degasser Needle Valve Spring EE-Degasser Needle Valve FF-Idle Needle Valve Spring Washer Clip GG-Idle Needle Valve Spring Washer HH-Idle Needle Valve Spring

JJ-Float Fulcrum Screw , KK-Float Level' Fulcrum Screw Gasket LL-Main Metering Jet Plug

MM-Main Metering Jet NN-Throttle Valve Plate Shaft Packing Retainer PP-Throttle Valve Plate Shaft Packing QQ-Throttle Valve Plate Shaft Outer Bushing I.R-Throttle Valve Plate Shaft Inner Bushing SS-Power By-Pass Jet

TT-Idle Needle Valve Packing UU-Idle Needle Valve Assembly VV-Float Needle Valve Seat Gasket

WW-Float Needle Valve Seat XX-Float Needle Valve Seat Lock Clip Screw YY-Float Needle Valve ZZ-Float Assembly

AB-Float Needle Valve Seat Lock Clip Screw Lock Washer

AC-Float Needle Valve Seat Lock Clip AD-Main Discharge Jet Stud Nut AE-Main Discharge Jet Stud Nut Cotter Pin AF-Main Discharge Jet Stud Washer AG-Main Discharge Jet Assembly AH-Main Discharge Jet Gasket AJ-Main Discharge Jet Stud

AK-Accelerating Pump Outlet Check Valve Ball Retainer

AL-Accelerating Pump Lever Bracket Screw AM-Accelerating Pump Lever Bracket Screw

Lock Washer ' AN-Accelerating Pump Lever Bracket AP-Accelerating Pump Pusa Rod Sleeve Packing AQ-Acceler~ting Pump Push Rod Sleeve AR-Accelerating Pump Outlet Check Valve Ball AS-Fuel Level Inspection Plug AT-Main Body Stud A U-Main Body Channel P lug , A V-Main Body

AW-Accelerating Pump Inlet Chcck Valve AX-Accelerating Pump IpJet Check Valve Plug A Y - Slow Idle Adjusting Screw Spring AZ-Slow Idle Adjusting Screw BA-Throttle Lever Stop Pin BC-Throttle \ ' alvE' Plate Shaft Outer Bushing BD-l hrottIe ,'alve Plate Shart Packing BE-Throttle Valve Plate Shaft Packing Retainer BF-Throttle Valve Plate Shaft BG-Throttle Lever BH-Throttle Lever Taper Pin BJ-Throttle Valve Plate Screw

BK-Throttle Valve Plate Screw Lock Washer BL-Accelerating Pump Push Rod Packing Nut

Lock Washer BM-Accelerating Pump Push Rod Rubber

Packing BN-Accelerating Pump Push Rod Felt Packing BP-Accelerating Pump Push Rod Packing Nut BQ-Accelerating 'Pump Push Rod and Link

Assembly l-Push Rod 2-Fulcrum Pin 3-Link

BR-Accelerating Pump Link Fulcrum Screw Nut Cotter Pin

BS- Acceleratlng Pump Link Fulcrum Screw Nut BT-Accelerating Pump Link Fulcrum Screw BU-Throttle'Valve Plate ' BV-Idle Discharge Channel Plug

B W - Main Body Channel Plug BX -Float Chamber Drain Plug BY-Degasser Needle Valve Seat Gasket BZ-Degasser Needle Valve Seat CA-Degasser Screw Lock Washer CB-Degasser Screw

Figure 200-Continued.

241

Page 8: Carburetor Stromberg B

Section II. DISASSEMBLY

139. Degasser Removal a. Remove Degassers (fig. 201). Both degasser assemblies are re­

moved in the same manner. Cut and remove the locking wire that secures the three degasser attaching screws. Remove the three screws and lock washers, and pull the degasser assembly from the main body. Remove the degasser gasket.

Figure 201. Removing degasser assembly.

b. Remove Degasser Needle Valve Parts. Remove the degasser needle valve and needle valve spring. With screw driver 41-8-1388, remove the degasser needle valve seat (fig. 202) and the seat gasket. The degasser assembly will not be disassembled. Defective degassers are replaced on an exchange basis.

140. Air Horn Removal and Disassembly a. Remove Air Horn (fig. 203). Cut and remove external locking

wires. Remove the 10 safety nuts and flat washers from the main body studs. Remove the two long fillister-head screws and lock washers from the top machined surface of the air horn. Lift the air horn from the main body.

242

b. E unscre suitab

c. E Plug ( nting mover vacuu

141.

a. 1 ing ea

b. 1 the ta

Page 9: Carburetor Stromberg B

es are re­wire that the three from the

degasser -S-1388, . gasket. egassers

locking 1e main ad lock , the air

RA PO 161775

Figure 202. Removing degasser needle valve seat.

b. Remove Vacuum Power P1'ston (fig. 204). Invert the air horn and unscrew and remove the vacuum power piston assembly, using a suitable spanner wrench.

c. Remove Accelerating Pump Discharge Jet and Vacuum Channel Plug (fig. 205). Screw the remover 41-R-2371-500 into the acceler­nting pump discharge jet and remove the jet by tapping on the re­mover handle with a small hammer. Unscrew and remove the vacuum channel plug.

141. Main Body Disassembly

a. Remove Venturi (fig. 206). Remove the two venturi after mark­ing each one for its barrel to insure correct installation at assembly.

b. Remove Accelerating Pump and Pump Lever (fig. 207). Straighten the tabs of the accelerating pump lever fulcrum screw lock washer.

243

Page 10: Carburetor Stromberg B

RAPD 161776

Ftgure 203. Removing air horn.

244

Page 11: Carburetor Stromberg B

HER

Figure 204. Removing vacuum power piston.

Figure 205. Removing accelerating pump discharge jet.

245

Page 12: Carburetor Stromberg B

RA PO 161m

Figure 206. Venturi removed.

Figure 207. Removing accelerating pump and pump lever.

246

Rerr. fulc] sterr der.

c. Ren crm the the fror atir sprl pur the

Page 13: Carburetor Stromberg B

A-ACCELERATING PUMP PISTON ANTI.vlSRATION SPRING

B-ACCELERATING PUMP PISTON AND STEM ASSEMBLY

C-ACCELERATING PUMP PISTON SPRING O-ACCElERATING PUMP PISTON

SPRING WASHER i-ACCELERATING PUMP PISTON

. FULCRUM SCREW i i

Jt'igure 208. Accelerating pump piston and pump lever parts-exploded view.

Remove the nut and lock washer from the accelerating pump lever fulcrum screw and remove the screw. Lift the lever, with the pump stem assembly, withdrawing the pump stem carefully from the cylin­der. Unhook the pump lever torsion spring from the lever.

c. Disa.ssemble Accelera.ting Pump and Pump Lever Parts (fig. 208). Remove the cotter pin and castellated nut from the pump stem ful· crum screw (E) and remove the screw. Remove the spring washer as the screw is withdrawn. Remove the antivibration spring (A) from the lower end of the accelerating pump stem (Model NA-Y5Gg) or from the pump cylinder (Model NA-Y5G). Compress the acceler­ating pump piston spring (C) and remove the spring washer. Slip the spring off the pump stem. Remove the needle bearing (J) from the pump lever, if the bearing is to be replaced (par. 143c). To remove the accelerating pump lever bracket, remove the locking 'Yire from

247

Page 14: Carburetor Stromberg B

Figure 209. Removing float assembly and float needle valve (Model NA-Y5G).

. the two bracket retaining screws and remove the two screws and lock washers (fig. 207).

d. Remove the Main Body Gasket.

Note. The gasket may be removed without removing the accelerating pump lever, if desired, by raising the push rod end of the lever and slipping the gasket out between the lever and the push rod.

e. Remove Float Assembly and Float Needle Valve (fig. 209). Remove the two float fulcrum screws and gaskets and lift the float assembly from the body. Remove the needle valve from the float lever.

j. Remove Float Needle Valve Seat (fig. 210). Remove the screw and lock washer that secure the float needle valve seat lock clip and re­move the clip. With screw driver 41-8-1388, remove the float needle valve seat and gasket.

g. Remove Main Discharge Jet Assembly (fig. 211). Remove the cotter pin and nut from the main discharge jet stud. Pull the main

248

disch1 two Ie

h. j

Remo remo, rolls f

i. 1 450, t

j. 1 the a accel( openi

k. mete1 a sCrt

l. j

216). in tht the i<

VA~

Page 15: Carburetor Stromberg B

lock

[)ump sket

Ove ably

and re­

loat

the ain

discharge jet assembly and the jjt gasket off the stud. Remove the two lead ball channel plugs (fig. 222) from the jet channels.

h. Remove Accelerating Pump Outlet Check Falve Ball (fig. 212). Remove the accelerating pump outlet check valve ball retainer, using remover 41-R-2371-500. Invert the body and catch the ball as it rolls from the channel.

i. Remove Power Bypass Jet (fig. 213). 'Using wrench 41-W-1573-450, unscrew and remove the power bypass jet from the main body.

j. Remove Accelerating Pump Inlet Check Valve (fig. 214). Remove the accelerating pump inlet check valve aceess plug and remove the accelerating pump check valve with a screw driver inserted through the opening for the plug.

k. Remove Main Metering Jets (fig. 215). Remove the two main metering jet access plugs and remove the main metering jets, using a screw driver inserted through the opening for the plug.

l. Remove Idle Needle Valve Assemblies (Model NA-Y5G3) (fig. 216). Unscrew the idle needle valve end fitting from the opening in the main body. Remove the hairpin type clip from the slot below the idle needle valve spring and remove the idle needle valve assembly,

flOAT NEEDLE} VALVE SEAT

LOCK CLIP SCREW ,

SCREWDRIVER-41-S-1388

FLOAT NEEDLE VAlVE SEAT

Figure 210. Removing float needle valve seat.

249

Page 16: Carburetor Stromberg B

250

{MAIN OISCHAR<:7e ' JET ASSEM8l Y

4---{ MAIN DISCHARGE MAIN DISCHARGE . ' JET GASKET

JET

Figure 211. Main discharge jet assembly and associated parts.

REMOVER-41-R~2371·500

" .' {ACCELERATING PUMP ounET CHECK

V VALVE BALL RETAINER

{

ACCELERATING PUMP Q- OUTlET CHECK

VALVE BALL

Figure 212. Removing accelerating pump outlet check valve parts.

from asseI Botf

m. cottE (fig. held shaf posi' for i thro thro seal rern' out thrc

n , (fig. rna,

Page 17: Carburetor Stromberg B

RA PO 161784

Figure 213. Removing power bypass Jet.

from the openings, catching the spring and spring washer as the valve assembly is withdrawn. Remove the idle needle valve packing. Both idle needle valve assemblies are removed in the same manner.

m. Remove Throttle Valve Parts (Model NA-Y5G3). Remove the cotter pin and nut from the accelerating pump link fulcrum screw (fig. 216) and remove the fulcrum screw. With the throttle valves held in fully closed position, scribe lines on the throttle valve plate shaft, both throttle valve plates and the main body to insure correct positioning at assembly. Be sure to mark each throttle valve plate for its barrel. Remove the two screws and 10ck washers from each throttle valve plate and remove the throttle valve plates and the throttle valve plate shaft. Remove the throttle va1ve plate shaft seal retainers (J and D, fig. 217) from each side of the main body and remove the throttle valve plate shaft seals (H and E, fig. 217). Drive out the throttle lever taper pin and remove the throttle lever from the throttle valve plate shaft.

n. Remove Idle Needle Valves and Throttle Pa.rts (Model NA-Y5G) (fig. 218). Unscrew and remove the two idle needle valves and re­move the needle valve springs. Detach the accelerating pump link

251

Page 18: Carburetor Stromberg B

Figure 214. Removing accelerating pump inlet check valve.

from the accelerating pump link lever (M) by removing the cotter pin, castellated nut, and fulcrum screw. Remove the accelerating pump lever clamp screw (R) with lock washer, and pull the link lever from the shaft. Remove the Woodruff key from the shaft. Remove the throttle valve plates and the shaft in the manner described in m above. Remove the throttle lever stop screw and the stop screw spring from the throttle lever. To remove the throttle lever, drive out the taper pin and pull the lever from the shaft.

o. Remove Idle Bleeds. Remove the idle bleed (Q, fig. 217) from each barrel, if necessary, using small pliers.

p. Remove Accelerating Pump Link and Push Rod Assembly (fig. 219). With the accelerating pump link detached from the throttle lever (n above), straighten the tabs of the accelerating pump push rod packing nut lock washer (Q), unscrew the push rod packing nut from the accelerating pump push rod sleeve (D) and pull the push rod from the sleeve. Remove the lock washer, the rubber packing, the felt packing, and the packing nut from the push rod (J). The push rod is secured to the push rod link with a fulcrum pin. It is seldom

252

neces~

damal sleeve 220) 1

body, the tb

q. l To re main

r. j

plate from driviI ~ain

Page 19: Carburetor Stromberg B

~tter

ting ever lOve d in irew rive

~om

,fig. t tle ush nut rod he

:Ish om

necessary to separate these parts unless the fulcrum pin is loose or damaged (par. 143c). Remove the accelerating pump push rod sleeve packing (0) from the accelerating pump push rod sleeve (fig. 220) using a small hooked wire. Remove the sleeve from the main body, tapping it with a plastic hammer. Be careful not to damage the threads on the lower end of the sleeve.

q. Remove Slow Idle Adjusting Screw (Model NA-Y6G3) (fig. 219). To remove the slow idle adjusting screw, simply unscrew it from the main body and remove the spring from the screw.

r. Remove Throttle Valve Plate Shaft Bushings. If the throttle valve plate shaft bushings are worn or damaged (par. 143g), remove them from the main body by pressing them out in an arbor PJ"ess or by driving them out with a suitable drift. Be careful not to damage the ~ain body.

Figure 215. Removing main metering jets.

253

Page 20: Carburetor Stromberg B

I~

____ ~. IDLE NEEDLE VALVE ASSEMBLY

Figure 216. Idle needle valve assembly and associated parts (Model NA-

s. Remove Plugs. Remove all channel plugs, the float d.rain plug and the two fuel level inspection plugs (F and P, fig.

t. Throttle Lever Stop Pin and Main Body Studs. I t is not to remove the throttle lever stop pin (G, fig. 219) unless the been broken off short. To remove the stop pin, drive out taining pin and pull the stop pin from the main body. Remove main body studs (fig. 215) that are damaged (par. 143g).

254

Page 21: Carburetor Stromberg B

') .

her .9). !try bas re­my

A-THROnu LeVER a-::.THROTTLE lEVER TAPER PIN C-'THROTTLE VALVE PLATE SHAFT ~THROTTLE VALVE PLATE SHAFT SEAL

,' RttAlNER a":;';"THROTTLE VALVE PLATE SHAFT SEAL p..:...THROmE VALVE PLATE SHAFT END

BUSHING G±l-THROTTJ.E VALVE P!,ATE . SHAFT END j'

.8USHING "' H.--lHROTTLE VALVE PLATE SHAFT SEAL ~THROTTLE vALVE PLATE

tqSHAFT SEAL RETAINER K;':"':'MAlN BODY L-THROmE VALVE PLATE SCREW

WASHER ~THROTTLE VALVE PLATE SCREW

l ~1'HROTTtE VALVE PLATE p....:'.:.THROTTLE VALVE PLATE SHAFT CENTER

BUSHING Q--tDLE BLEED I-i-THROTTLE LEVER STOP PIN TApeR PIN ~T'1RO'J1U LEVER STOP PIN

Figure 217. Throttle parts (Model NA-Y5G3)-exploded view.

255

Page 22: Carburetor Stromberg B

A-SLOW IDLE ADJUSTING SCREW B-SLOW tOLE ADJUSTING SCREW SPRING C-THROTTLE LEVER SCREW NUT D-THROTTLE LEVER I-THROTTLE LEVER SCREW F-THROlTLE VALVE PLATE SHAFT

G- WOODRUFF KEY H-MAIN BODY J-IDLE ADJUSTING NEEDLE VALVE SPRING k-IDLE ADJUSTING NEEDLE VALVE L-ACCElERATING PUMP LINK FULCRUM

SCREW M-ACCElERATING PUMP LINK LEVER

04-$

!-, N-ACCELERATING PUMP LINK FULCRUM

SCREW NUT '-ACCELERATING PUMP LINK FULCRUM

SCREW NUT COTTER PIN Q-ACCElERATING PUMP LEVER CLAMP

SCREW LOCK WASHER R-ACCELERAnNG PUMP LEVER CLAMP

SCREW S- THROTTlE VALVE PLATE SCREW LOCK

WASHER T-THROTTlE VALVE PLATE SCREW U- THROTTLE VALVE PLATE

RA PO 161789

Figure 218. Throttle parts and idle needle valve-exploded view (Model N A-Y5G)

Figu'

Page 23: Carburetor Stromberg B

A-SLOW IDLE ADJUSTING SCREW I-SLOW IDLE ADJUSTING SCREW SPRING C-ACCELERATING PUMP PUSH ROD SLEEVE

. PACKING . D-ACCElERATING PUMP PUSH ROD SLEEVE I-MAIN 80DY F-FUE~ LEVER INSPECTION PLUG

G-THROTTlE LEVER STOP PIN H-THROTTlE LEVER STOP PIN TAPER PIN J-ACCElERATING PUMP PUSH ROD AND LINK

ASSEMBLY 1. PUSH ROD 2. fULCRUM PIN 3. LINK

K-ACCELERATING PUMP PUSH ROD PACKING NUT

L-ACCELERATING PUMP PUSH ROD FELT PACKING

M-ACCElERATING PUMP PUSH ROD RUBBER PACKING

N-FLOAT CHAMBER DRAIN PLUG P-FUEl LEVEL INSPECTION PLUG Q-ACCELERATING PUMP PUSH ROD PACKING

NUT LOCK WASHER

RA PO 161790

Figure 219. Accelerating pump push rod parts and slow idle adjusting screw (Model NA-Y5G3).

257

Page 24: Carburetor Stromberg B

Figure 220. Removing accelerating pump push rod sleeve packing.

Section III. CLEANING AND INSPECTION

142. Cleaning Immerse all parts to be cleaned in dry-cleaning solvent or volatile

mineral spirits. Do not allow the parts to rest on the bottom of the container where possible sludge accumulation may retard the cleaning process. Remove dirt with a stiff bristle paint brush. Dry the parts and blow compressed air through all body channels. Be sure all parts are absolutely clean.

Note. It is advisable to reverse the flow of compressed air through all passages to insure removal of all dirt particles. N ever use a wire or drill to clean jets

143. Inspection a. Preliminary. The repair kit (fig. 221) provides all parts that

must be replaced in the carburetor when it is assembled. Spare parts (such as screws, lock washers, plugs, etc.) need not be replaced unless the original parts are damaged. Discard all parts that are to be replaced.

258

b. j

and d dischf1 (table Repai

c . • accelE ing f( ating that that push

d. pin b into are iI and I

e. paSSf

Repl j.

depo and valv, Rep]

g. threi thre: the ' bon char Ip.sp Rep

h. vah vah See fect

~.

Che reql

Page 25: Carburetor Stromberg B

ile he :lg ·ts tIl

es

lt ts ss >e

b. Inspect air horn. Inspect the air horn for cracks, bent flanges, and damaged threads. Check the opening in the accelerating pump discharge jet with a drill of the correct size for the carburetor involved (table XIII). Examine the machined surfaces for abrasions and nicks. Repair or replace a damaged air horn.

c. Inspect Accelerating Pump and Pump Lever Parts. Examine the accelerating pump lever for distortion. Check the lever needle bear­ing for noticeable wear. Look for damaged threads on the acceler­ating pump push rod sleeve and in the push rod packing nut. See that the accelerating pump link fulcrum pin is securely riveted and that the push rod is free from abrasions and operates freely in the push rod sleeve. Replace worn or damaged parts.

d. Inspect Float Assembly. Inspect the float assembly for cracks, pin holes, and badly corroded spots that might cause leakage of fuel into the float. Inspect riveted and soldered joints to see that they are in good condition and tight. Inspect the fulcrum screws for wear and damaged threads. Replace worn or damaged parts.

e. Inspect Main Discharge Jet Assembly. Check the nozzles and passages to see that they are clean and free from any foreign matter. Replace a defective main discharge jet assembly.

j. Inspect Throttle Paris. Check the throttle valve plates for carbon deposits, warping, and for damaged edges. Remove carbon deposits and minor abrasions with fine emory cloth. Examine the throttle valve plate shaft for distortion and worn or damaged bearing surfaces. Replace worn or damaged parts.

g. Inspect Main Body. Inspect the main body for cracks, damaged threads, and bent flanges. Inspect the main body studs for stripped threads. See that they are secure and in good condition. Examine the throttle barrels for scratches and carbon deposits. Remove car­bon deposits and minor abrasions with fine emery cloth. See that all

. channel passages are clean. Check machined surfaces for abrasions. Ip.spect throttle valve plate shaft bushings for wear and abrasions. Repair or replace a damaged main body.

h. Inspect Degassers. Inspect the degasser needle valves and needle valve seats for corrosion. Replace de gasser needle valves and needle valve seats as a unit. Inspect the degasser assemblies for breaks. See that electrical connections are clean and free from corrosion. De­fective degasser assemblies will be replaced on an exchange basis.

i. Miscellaneous. Inspect aU springs for breaks and distortion. Check body plugs for darnaged threads. Replace defective parts as required.

259

Page 26: Carburetor Stromberg B

260 .

Page 27: Carburetor Stromberg B

~ 0--

·-----""""'--..",,---__ a._~~,,'.~~-~~~,

Quantitv in kit

A-Main Discharge Jet Utl1jA.t;lL- _________________________________________________________________ _

B-Vacuum Power Piston Assembly _ ___________________________________ _________________________ 1 C-Float Needle Valve Scat GaskeL __________ ______________ ____ _________________________________ 4 D-Float Lever Fulcrum Screw Gasket-___ _ _ _ __ __ _ _ ____ ___ _ _ ____ _ _ ___ __ ___ _ _ __ __ _____ _ _ _ _ _ ____ _ _ _ 3 E-Accelerating Pump Piston and Stem Assembly _______________ __ _____ ____________________ ____ _ F-Main Body Gasket __________________________________________________________________________ _

G-Float Needle

J-Power By-Pass Jet Assembly ________________________________________________________________ _

K-Accclerating Pump Inlet Check L-Main Body Stud Nut WasheL____________ _____ ______________________________ _____ ___________ 2

M-Main Metering Jet- _ _ __ ______________________________________________________________________ 2 N-Main Body Stud Nut- _ _ _ ____________________________________________________________________ 10 P-Accelerating Pump Link Fulcrum Screw __ ______________________________ ._____________________ 1 Q-Accelerating Pump Link and Pump Stem Fulcrum Screw NuL______ ______ ________________ __ 2 R-Throttle Valve Plate Screw ___________________________________________________________________ 4 S-Channel Plug----- _ __ ____ _ _ _ ______ __ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ _ _ _ _______ _ _ 8

T-Accelerating Pump Outlet Check Valve U-Main Discharge Jet Channel Plug Lead V-Throttle Valve Plate Screw Lock Washer__________ _________ ____ __ _____ ____ ___ __ ______________ 4

W-Acceleratlng Pump Push Rod Packing Nut Lock Washer ____ _________ _____ _________________ _ X-Idle Needle Valve Assembly _______________________________________________________________ " _ _ 2

Y-Accel~ratlng Pump Push Rod Nut Felt Packing----------------------------------------------Z-Main Discharge Jet Stud Nut Cotter Pin ____________________________________________________ _

AA-AcceleratingPump Link and Pump Stem Fulcrum Screw Nut CotterPin___ ___ _________ ______ _ 2 BB-Degasser Needle Valve Seat Gasket- ___ ____________ ___________ __ ___ ___________ ________ _______ _

CC-Degasser Assembly DD-Accelerating Pump Sleeve tmd Throttle Valve Plate Shaft Packing . ________________________ _

EE-Acceleratlng Pump Push Rod Nut Rubber Packing ------------------------------------------FF-IdleNeedle Valve Packlng.--------- ---------- --- ------------------------ -____________________ 2

Figure 221. Typical repair kit for Model NA-Y5G3 carburetor.

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Section IV. ASSEMBLY

144. Main Body Assembly a. Install Throttle Lever Stop Pin and Main Body Studs. If the

throttle lever stop pin (fig. 219] was removed, drive a new pin into place and secure it with the taper pin. Install any main body studs (fig. 215) that were removed at disassembly.

b. Install Plugs. Install the float chamber drain plug (N, fig. 219), the two fuel level inspection plugs and the main body channel plugs.

Note. Apply a thin coat of shellac to the threads of all plugs, being careful that no shellac enters the fuel channels.

c. Install Throttle Valve Plate Shaft Bushings and Seals (fig. 217). Install the throttle valve plate shaft end bushings in the body, pressing them into position. These bushings are available in standard size and first, second, or third oversize. Use bushings of correct size to insure proper fit between the bushings and the body as well as between the bushings and the shaft. Line ream the bushings to correct size. Install the two throttle valve plate shaft seals, one in each outer opening of the shaft and install the seal retainers.

d. Install Slow Idle Adjusting Screw (Model NA-Y5G3) (fig. 219). Install the spring on the slow idle adjusting screw and install the screw opening in the body. See paragraph 149c for slow idle screw adjustment.

e. Install Accelerating Pump Link and Push Rod Assembly (fig. 219). Install the accelerating pump push rod sleeve packing (0) in the accelerating pump push rod sleeve and install the sleeve in the main body. Place the accelerating pump push rod packing nut, (K) the felt packing, the rubber packing, and the packing nut lock washer (Q) on the push rod, apply three drops of No. 30 SAE engine oil to the push rod and install the push rod in the sleeve. Tighten the packing nut securely and bend the packing nut lock washer tabs over the nut an9-. sleeve.

j. Install Idle Bleeds (fig. 217). If the idle bleeds were removed from the barrels, install new bleeds in the openings in the barrels.

g. Install Throttle Lever (figs. 217 .or 218). Install the throttle lever on the shaft, lining up the taper pin holes, and install the taper pin.

h. Install Throttle Valve Plate Shaft and Valve Plates (figs. 217 or 218}. Install the throttle valve plate shaft in the main body and install the throttle valve plates, matching the scribe marks made at disassembly, and making sure that each throttle plate is in its proper barrel (par. 141m). Install the two valve plate screws and lock washers for each valve plate, but do not tighten. With the throttle valve plates in fully closed position, hold the main body to the light and check for an even margin of light around the circumference of the valve plates. Move the plates slightly, if necessary, to position

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them so that a minimunl margin of light appears evenly around each plate. Tighten the throttle valve plate screws securely. On the Model NA-Y5G, install the slow idle adjusting screw, with the spring. Refer to paragraph 149c for slow idle adjustment. Attach the accel­erating pump push rod link to the throttle lever (Model NA-Y5G3) or the accelerating pump lever (Model NA-Y5G) , with the link fulcrum screw and nut, and replace the cotter pin.

i. Install Accelerating Pump Link Lever (Model NA-Y5G) (fig. 218). Install the Woodruff key in the slot in the throttle valve plate shaft and install the accelerating pump link lever. Install the accelerating pump lever clamp screw and the lock washer.

j. install idle Needle Valve Assemblies (Model NA-Y5G3) (fig. 216). Install the packing on the end of each needle valve. Hold the spring and spring washer in position and slip the valve through the openings in the main body, the spring, and washer. Insert the valve end in its opening in the body and screw into place enough to hold. Com­press the spring and install the spring retaining clip. Refer to para­graph 149a for idle needle valve adjustment .

k. Install Idle Adjusting Needle Valves (Model NA- Y5G) (fig. 218). Install the idle adjusting needle valve springs on the idle adjusting needle valves and screw them into the lnain body. Refer to paragraph 149b for idle needle valve adjustment.

l. Install Main Metering Jets (fig. 215). Install the main metering jets in the main body, using a screw driver inserted through the openings for the main metering jet access plugs. Install the two main metering jet access plugs.

m. install Accelerating Pump inlet Check Valve (fig. 214). Install the accelerating pump inlet check valve with a screw driver inserted through the opening for the check valve access plug. Install the inlet check valve access plug.

n. Install Power Bypass Jet (fig. 213). Install the power bypass jet in the main body, using the wrench 41-W-1573-450.

o. Install Accelerating Pump Outlet Check Valve Ball (fig. 212). Install the a.ccelerating pump outlet check valve ball in the main body and install the ball retainer, driving the retainer in flush with the body · surface.

p. Install Main Discharge Jet Assembly (fig. 211). Make sure that all channels are perfectly clean. Install the two lead ball channel plugs (fig. 222), using a suitable punch to seat the plugs. If the jet stud was removed, install it in position and tighten securely. Place the main discharge jet gasket in position and install the jet assembly and the (castellated) stud nut, tighten securely, and replace the cotter pIn .

g. Install Float Needle Valve Seat, Needle Valve and Float Assembly. Install the float needle valve seat and the needle valve seat gasket . Tighten the seat with the screw driver 41-8-1388 (fig. 210). Install

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Figure 222. Lead ball channel plugs in main discharge jet.

the float needle valve seat lock clip, with the clip screw and lock washer.

Note. The lock clip may be installed after the fuel level has been checked and adjusted, if desired (par. 147).

Attach the float needle valve to the float lever and pl!1ce the float assembly in position, with the needle valve in its seat. Install the two float fulcrum screws and gaskets ('fig. 223). Test the fuel level (par. 147).

r. Assemble Accelerating Pump Piston and Pump Lever Parts (-ag. 208). Install the accelerating pump lever needle bearing in the lever. Install the accelerating pump piston spring on the pump piston stem, compress the spring and install the spring washer Attach the accelerating pump piston stem to the accelerating pump lever with the fulcrum screw, the spring washer (between the stem and the extension ear of 'the lever), and the fulcrum screw nut and replace the cotter pin. Attach the accelerating pump piston antivibration spring to the pump piston, 'fitting the small diameter of the spring into the recess in the bottom of the piston (Model NA-Y5G3) . For the Model NA-Y5G, install the antivibration spring in the pump cylinder, with the small dia,meter uppermost.

s. Install Accelerating Pump Lever Bracket (fig. 224). Place the accelerating pump lever bracket in position on the main body, and install the two bracket screws and lock washers. Tighten the screws and secure with locking wire.

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fLOAT ASSEMBLY

FLOAT fULCRUM SCREW GASKET

FLO~ T. fULCRUM SCREW

Figure 223. Float assembly and associated parts.

t. Install Main Body Gasket and Accelerating Pump Lever (fig. 224). Place the main body gasket in position on the body. Install the accelerating pump piston assembly in the pump cylinder, being careful to prevent curling or damage to the leather piston. Aline the accelerat­ing pump lever with the holes in the pump lever bracket and install the accelerating pump lever fulcrum screw, the accelerating pump lever torsion spring, lock washer, and nut. Engage the hooks of the torsion spring in position and tighten the nut securely. Bend the tabs of the lock washer over the nut.

u. Venturi. Install the two venturi (fig. 225) in position in the body, with the slots opposite the accelerating pump check valve.

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G-ACCElERAnNG PUMP lEVER TOR SPRING

H-ACCELERATING ,PUMP lEVER J-ACCELERAnNG PUMP lEVER BRA

SCREW K-ACcelERATlNG PUMP l~ER BRA

• SCREW LOCK WASHER L-ACCELERAnNG·P;UMP lEVER BRA

.A PD 161195 1

Figure ~e4. Accelerating pump lever and pi8ton pari8.

145. Air Horn Assembly and Installation

a. Install Accelerating ·Pump Discharge Jet and Vacuum Channel Plug (fig. 205). Install the accelerating pump discharge jet, driving it in flush with the surface of the air horn. Install the vacuum channel plug.

b. Install Vacuum Power Piston (fig. 204). Install the vacuum power piston, using a suitable spanner wrench.

c. Install Air Horn (fig. 203). Install the air horn in position on the main body and install the 10 flat washers and sa,fety nuts on the main body studs. Install the two air horn screws and washers. Tighten the screws and the safety nuts evenly and securely.

266

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d. Install Locking Wire. After testing the accelerating pump capac­ity (par. 148), install locking wire to secure the float chamber drain plug, the two float fulcrum screws and the two fuel level inspection plugs.

146. Degasser Installation

a. Install Degasser Needle Valve Seat (fig. 202). Install the degasser needle valve seats and the seat gaskets. Tighten the seats with the screw driver 41-8-1388.

b. Install Degasser Needle Valves (fig. 201). Place the degasser needle valve springs on the needle valves and insert the valves in the seats.

c. Install Degasser (fig. 201). Place the degasser gaskets and the degasser a.ssemblies in position, and install the three degasser screws and lock washers for each degasser. Tighten the screws firmly and secure with locking wire.

RAPD 334229

Figure 225. CorreGt position of venturi.

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Section V. TESTS AND ADJUSTMENTS

147. Fuel Level and Leakage a. Test for Fuel' Level. Mount the assembled main body so that

the upper surface is level. Connect a source of fuel supply to the fuel inlet as shown in figure 226. Place the fuel container at the correct height (a,pprx. 3 ft. above the fuel inlet port) to allow fuel to enter the carburetor at less than 1 psi. When the fuel stops rising in the float ehamber, the level should be at the lower edge (plus or minus one thirty-second in.) of the fuel level inspection plug opening.

b. To Change Fuel Level. If the fuel level must be changed, use a gasket of different thickness under the float needle valve seat. Gas­kets (C, fig. 221) of four different thicknesses are supplied in the carburetor repair kit. A thinner gasket will raise the fuel level, while a thicker gasket will lower it.

c. Test for Fuel Leakage. After the fuel level has been established (a above), test for fuel leakage. Using the same set-up (fig. 226), raise the fuel container to a height (about 15~ ft.) sufficient to pro­duce a pressure of 5 psi at the fuel inlet port. Maintain this pressure for 15 minutes. The fuel level should not rise during the test period.

d. To Correct Fuel Leakage at Needle Valve. If the fuel level rises during the leakage test (fig. 226), check the end play of the float

Figure 2~6. Test set-up for fuel level and leakage.

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Page 35: Carburetor Stromberg B

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lever. The distance between the float lever and the boss inside the main body should be from 0.005 to 0.020 inch. If the end play does not come within these limits, change the float fulcrum screw gaskets. Gaskets are supplied in three different thicknesses. A thinner gasket will decrease end play while a thicker gasket will increase it. If changing the end play of the float lever does not correct the leakage, replace the float needle valve and needle valve seat.

e. Plugs. During the 15-minute test period, observe all main body plugs for leakage, and correct as required.

148. Accelerating Pump Capacity

a., General. To test the operating efficiency of the accelerating pump, measure the amount of fuel delivered by 10 full strokes of the pump, using the burette gage 41-G-98-20.

b. Procedure. With the assembled carburetor mounted level, con­nect the burette gage 41-G-98-20 (fig. 227) to the fuel inlet with flexible tubing and tube connector. Pour fuel into the burette gage until level approaches the top. Operate the throttle several times to fill the accelerating pump systam, and refill the burette gage to "0" marking. Then move the throttle from fully closed position to the fully open position. Hold the throttle open until fuel stops flowing, then close. Keep the .throttle closed for a few seconds to permit the

Figure 227 . Measuring accelerating pump capacity.

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Page 36: Carburetor Stromberg B

pump system to refill before making. another stroke. Repeat this procedure until 10 full strokes have been made. Observe the amount of fuel discharged from the burette gage. For the Model NA-Y5G, this amount should be from 85 to 95 cubic centimeters and for the Model NA-Y5G3 it should be from 145 to 165 cubic centimeters.

c. Correction. Failure of the accelerating pump to deliver the required amount of fuel may be caused by a worn or damaged pump piston, a weak or broken piston spring, a damaged main body (scratched or damaged pump cylinder), or by worn or damaged parts in the pump operating linkage. Replace defective parts as required.

149. Idle Needle Valves and Slow Idle Screw

a. Adjust Idle Needle Valves (Model NA-Y5G3). To make initial idle needle valve adjustment, turn each needle valve assembly in until the valve seats lightly, then back it out one-half turn. Adjust both idle needle valve assemblies exactly the same. Final adjustment may be made after the carburetor has been installed.

b. Adjust Idle Needle Valves (Model NA-Y5G). To make initial idle needle valve adjustment, turn each needle valve in until it seats lightly, then back out one full turn. Adjust both idle needle valves the same. Final adjustment may be made after the carburetor has been installed.

c. Adjust Slow Idle Screw (Either Model). Turn the slow idle adjusting screw in until it contacts the throttle lever, then back it out one fo,!lrth turn. Final adjustment may be made after the carburetor has been installed.

150. Degasser Adjustment

a. General. Each degasser is set at the factory so that the needle valve will move 0.015 inch from its seat at 21 inches of vacuum and will seat when vacuum reaches 22% inches. An adjusting scr~w provides a means of setting the mechanism so that the needle valve seats at the proper time. Counterclockwise movement of the adjust­ing screw is limited by a stop collar, in order to furnish a known start­ing point for making adjustment. With the adjusting screw against the stop, 19 inches of vacuum will seat the needle valve. If the original setting is lost, adjust the degassers in the manner described in b below.

b. Procedure. Cut and remove the locking wire and lead seal that secures the adjusting screw cover and remove the cover. Turn the adjusting screw counterclockwise until it contacts the stop collar. Then turn the screw clockwise for 12 notches. (The notches are inside the mechanism, but can be felt as the screw is turned.) Set, both degassers the same.

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Page 37: Carburetor Stromberg B

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c. Test. With the carburetor installed, start the engine and after it has warmed up, accelerate to about 2,000 rpm. Close the throttle suddenly and observe the ma:nner in which the engine recovers as it returns to idling speed. There should be a slight "roll" just as the engine resumes idling speed. ("Engine roll" means a slight indica­tion of stall and quick recovery.) If there is a very decided "roll," or if the engine stalls, turn the adjusting screws clockwise one or two notches. If there is no "roll," turn the screws counterclockwise one or two notches. Be sure both degassers are adjusted the same.

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When the adjustment has beeh completed,. install the adjustment screw covers. Secure with locking wire.

Note. If the carburetor is to be stored before being put back into service, drain all fuel to prevent formation of gum substances. Remove the float chamber drain plug from the bottom of the main body and allow fuel tG drain. Operate the throttle several times to empty the pump system, and invert the carburetor to completely drain any fuel trapped in the channels. Install the drain plug and plug or tape both fuel inlet openings, cover the top and bottom flange surfaces to exclude dirt particles or other foreign matter.

271

Page 38: Carburetor Stromberg B

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DEPARTMENT OF THE ARMY lJ~ ®Qrn®~~ TECHNICAL MANUAL

DEPARTMENT OF THE AIR lfinl Wo1d7[S(fU(fUfA\d1 FORCE TECHNICAL ORDER U lJlJ UQU -U Cilll0l0~-U

FORMERLY TM 9-18268

CARBURETORS

(STROMBERG)