Monobloc Carburettor

Carburettor Problems

Poor starting and erratic tick over is usually caused by wear between the throttle valve and the body. Fitting a new slide in a worn body is like fitting a new chain to old sprockets, a waste of time. Wear is likely to be apparent as early as 5,000 miles, but can be rectified by boring the body oversize and fitting a sleeve to the slide. The materials used in this process will last a lot longer than the original. This is preferable to fitting a non-original later type of concentric carburettor. The new Monobloc carburettors that are now available have improved materials.  The prices for re-sleeving are found under RES169 or RES170 for a complete overhaul. Or replace the basics and seals with our overhaul pack here (monobloc only)

Monobloc carburettor settings chart

1955 saw a completely new carburettor being manufactured, that had the float chamber cast in one piece with the mixing chamber and called the ‘Monobloc’, these are types 375, 376, and 389. Each type number indicates a different size of casting. Each casting was machined to any one of several bore sizes. Therefore when searching for a replacement carburettor, the bore or choke size is needed in addition to the type. The suffix shown after the type on the flange indicates which jets, float chamber and to which machine it was originally fitted, it is irrelevant providing the body is of the correct size and type and the correct jets etc are used. The swinging arm models were always fitted with air cleaners connected by a rubber hose to the carburettor.

Mixing chamber tops can have one, two or no threaded holes for cable adjusters; there is an adjuster on the carburettor OR in the cable, not both.

Model Part number of complete new carburettor Years Carburettor Type Bore Main Jet Slide Needle Position Needle Jet Pilot Jet Mixing Chamber Top
NH/HT3 376/16NH 1955-58 376 1 200 3.5 3 .106 25 376/065
VH 376/17VH 1955-58 376 1 1/16 200 3.5 3 .106 30 376/099
HT5 376/17HT 1956-58 376 1 1/16 200 3 3 .106T 30 376/099
HS MK III 389/19HS 1956-58 389 1 3/16 380 3.5 3 .106 30 389/099
VB 376/16VB 1955-58 376 1 220 5 2 .106 30 376/065
KH 376/16VB 1955-57 376 1 200 3.5 3 .106 30 376/065
FH 376/17FH 1955-58 376 1 1/16 240 3.5 3 .106 25 376/099

Gasket Sets

Part No

Description

Model

Years

GS275

Amal type 6 carburettor 74,75,274,275 1939-54

GS276

Amal type 6 carburettor 76,276 1939-54

GS289

Amal type 6 carburettor 89,289 1939-54

GS375

Amal Monobloc carburettor 375 1954-58

GS376

Amal Monobloc carburettor 376 1954-58

GS389

Amal Monobloc carburettor 389 1954-58

622/208

Amal Concentric Mk1

622/209

Amal Concentric Mk1 1/2

For jetting application please select your bike make from the following list.

Ariel, BSA,

Part No.

Description

Carburettor

Models

PACK-ADV-001

Monobloc carb overhaul pack All All

A7/1057/14

Insulating spacer 7/8 bore x 1/8 thick

A7/1057/17

Insulating spacer 1 1/16 bore x 1/8 thick

4/035

Cable adjuster (lock nut is 5/077) All

4/046

Choke spring All

4/137A

Blanking plug, when no choke fitted All

4/148

Air screw spring All

4/230

Needle clip All

4/235

Cap retaining spring clip, for top with adjuster 375/376 NH,VB,KH

4/241

Screw for cap retaining spring clip All

4/276

Cap retaining spring clip, for top without adjuster 375/376 FH,VH,HT5

5/047

Air slide guide tube 375

5/077

Cable adjuster lock nut (adjuster is 4/035) All

6/047

Guide tube for air slide 376

14/026

Spigot for push on petrol pipe (not as illustrated) All

14/042

Gland nut 1/4 BSP for petrol taps, threaded banjos, ukuleles etc

14/042Q

Gland nut 1/4 BSP for petrol taps, threaded banjos, ukuleles etc, stainless

29/057

Guide tube, air valve 389

29/110

Inlet adapter for air filter hose or offset pancake filters 375

29/201

Cap spring for carburetter. top with cable adjuster 389

29/301

Cap spring for carburetter. top without cable adjuster 389

116/162

Fibre washer, pilot jet All

244/765

‘O’ ring for manifold joint, 1 3/8 outside diameter 375/376

244/1048

‘O’ ring for manifold joint, 1 ½ outside diameter 376/389

332/017

Air screw All

343/011

Tickler body All

375/060/3

Throttle slide No. 3 cutaway 375

375/060/35

Throttle slide No. 3 1/2 cutaway 375

375/060/4

Throttle slide No. 4 cutaway 375

375/061

Spring for throttle slide 375

375/062

Air slide 375

375/063

Needle 375

375/064

Mixing chamber top, 2 adjuster type 375

375/065

Mixing chamber top ring 375

375/066

Bellmouth 375

375/067

Jet block washer 375

375/099

Mixing chamber top, no adjuster type 375

375/107

Mixing chamber top, 1 adjuster 375

376/15

Monobloc carburetter 15/16″ bore 376

376/16

Monobloc carburetter 1″ bore 376 NH,VB,KH

376/17

Monobloc carburetter 1 1/16″ bore 376 VH,HT5,FH

State model or specify jets and slide required when ordering above carburetters

376/001

Carburetter body 15/16″ 376

376/002

Carburetter body, bare, new and genuine, 1″ 376 NH,VB,KH

376/003

Carburetter body 1 1/16″ 376 VH,HT5,FH

376/055

Jet block 15/16″ 376

376/056

Jet block 1″ 376 NH,VB,KH

376/057

Jet block 1 1/16 376 VH,HT5,FH

376/060/3

Throttle slide No. 3 cutaway 376 HT5

376/060/35

Throttle slide No. 3 1/2 cutaway 376 NH,VH,KH,FH

376/060/4

Throttle slide No. 4 cutaway 376

376/060/5

Throttle slide, No.5 cutaway 376 VB

376/061

Spring, throttle slide 376

376/062

Air valve (choke slide) 376

376/063

Needle 376

376/064

Carburetter top tapped for 2 cable adjusters 376 NH, VB, KH

376/065

Threaded ring, retaining carburetter top 376

376/066

Bellmouth, chrome 376

376/067

Jet block washer 376/389

376/068

Idle screw All

376/069

Idle screw spring All

376/070

Screw, locking jet block All

376/072/105

Needle jet number .105 All

376/072/106

Needle jet number .106 All All Ariels

376/072/107

Needle jet number .107 All

376/073

Main jet holder All

376/074

Fibre washer, main jet holder All

376/075

Main jet cover nut All

376/076/15

Pilot jet number 15 All

376/076/20

Pilot jet number 20 All

376/076/25

Pilot jet number 25 All NH/HT3

376/076/30

Pilot jet number 30 All VH,HT5,HS,VB,KH

376/077

Float cover All

376/078

Float cover gasket All

376/079

Float chamber cover screw All

376/083

Float All

376/086

Tickler button All

376/087

Tickler spring All

376/088

Float needle seating All

376/089

Float needle, ‘Viton’ tipped! Ooooh er! All

376/090

Fuel banjo, single threaded inlet, dull chrome All All Ariels

376/091

Fuel banjo bolt All

376/092

Fibre washer, fuel banjo bolt All

376/093

Petrol filter All

376/094

Float spacer All

376/095

Pilot jet cover nut All

376/097M

Fuel banjo, push on pipe (metal) 1 pipe 360 degrees apart All

376/098

Fuel banjo, push on pipe (metal) 2 pipes 90 degrees apart All

376/099

Carburetter top for 2 mid-adjuster cables 376 FH, VH, HT

Main Jets

Main jet (add size to part no. e.g. 376/100/120) All

376/101

Mixing chamber top with rod operated choke 376 KH

376/108

Fuel banjo, double threaded inlet All

376/110

Inlet adapter for air filter hose or offset pancake filters 376

376/139

Fuel banjo, push on pipe, 2 pipes150 degrees apart

376/140

Extended jet holder for twin carburetters

389/18

Monobloc carburetter 1 1/8″ bore 389

389/18.5

Monobloc carburetter 1 5/32″ bore 389

389/19

Monobloc carburetter 1 3/16″ bore 389 HS

State model or specify jets and slide required when ordering above carburetters

389/060/3

Throttle slide No. 3 cutaway 389

389/060/35

Throttle slide No. 3.5 cutaway 389

389/060/4

Throttle slide No. 4 cutaway 389

389/061

Throttle return spring 389

389/062

Air valve (choke slide) 389

389/063

Taper needle 389

389/064

Mixing chamber top, 2 adjuster type 389

389/065

Top cap retaining ring 389

389/066

Bell mouth (not used on Ariels originally) 389

389/099

Mixing chamber top, non adjuster type 389 HS

389/107

Mixing chamber top, 1 adjuster type 389

389/110

Inlet adapter for air filter hose or offset pancake filters 389

S21-4

Spigot for soldering to copper ¼” pipe, as illustrated Any

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