This is a throttle needle to fit original Amal Type 5GP Racing Type carburettors. This is the 'Weak'' type needle (identified by a '6' after the number), but we can also supply the alternate 'Normal' type - See listing for more detail - for that, see Item 1142.

Price is Each

Note - these needes are UK manufactured by a specialist carburettor engineer, to the original Amal needle dimensions.  As per originals, they are stamped with the GP model and type designate (as GP needles were specific to the GP size type and were available in two types - 'Normal' or 'Weak').

This 5GP model of the GP carb was the type fitted to the shortstroke DOHC Featherbed Manx models, pictures attached are of my own 1955 DOHC Manx fitted with a similar carb

  

Background for GP Carbs:

The GP carburettor was introduced in the early 1950's and was available in a number of different body sizes (i.e. the diameter of the throttle slide) - as the size of the throttle slide bore increased, the numbering of the GP carb model number decreased - i.e. 15GP was the smallest size (comparable to the 15TT carb, and actually quite rare to find), 10GP (comparable to 10TT carbs, and fitted to the later Longstroke Featherbed Manx Nortons - I think 1952-53?), then 5GP, then 3GP.  The range of inlet tract bore sizes for these GP variants is shown below:

15GP Carb:     7/8" To 1 & 1/16"

10GP Carb:     1 & 1/16" To 1 & 7/32" (Replaced the RN carb on late Longstroke Manx Nortons @1952/53)

5GP Carb:     1 & 7/32" To 1 & 3/8"   (Used on most short stroke DOHC Manx Nortons)

3GP Carb:     1 & 3/8" To 1 & 1/2"

The accompanyning photograph shows a line up of 4 racing carb types - a 10TT, 10GP, 5GP and 3 GP, to show the different carb type bodies - with the model this needle is to fit ringed in RED.

The GP carburettor design was an improvement on the earlier TT and RN carb design, in that it had the needle to one side of the throttle body, and fuel enters the choke through a spray tube inclined to one side, rather than from directly underneath as on earlier designs - giving the shortest flow.

To go with this, and to give a more sensitive tuning control - each GP carburettor type had two types of throttle needle available, with a different taper - the 'Normal' type was identified by just having the model type stamped on it - i.e 'GP', or the 'Weak' type which was identified by having a '6' after the model number, i.e. 'GP6'.

Both the 15GP and the 10 GP used a needle stamped just 'GP' or 'GP6', while later 5GP and 3GP type carbs had a needle with that number on it (and a corresponding Weak needle followed by a 6 after the number).

A good starting point when setting up a carb is to look at which of the two needle types was originally fitted for your model - but as so many factors can vary the performance of an individual engine (i.e. fuel used/atmospheric conditions/condition and tuning of engine) - it is often prudent to obtain one of each type of needle and satisfy yourself which runs best (using the original Amal GP setting up instructions).

 

This is a throttle needle to fit original Amal Type 3GP Racing Type carburettors. This is the 'Normal' type needle, but we can also supply the alternate 'Weak' type (identified by a '6' after the number) - for that, see Item 1145.

Price is Each

Note - these needes are UK manufactured by a specialist carburettor engineer, to the original Amal needle dimensions.  As per originals, they are stamped with the GP model and type designate (as GP needles were specific to the GP size type and were available in two types - 'Normal' or 'Weak').

I believe this large 3GP version of the GP carb was fitted to later Shortstroke Manx DOHC models (although the even larger Amal GP2 was fitted in the last year of production)

Background for GP Carbs:

The GP carburettor was introduced in the early 1950's and was available in a number of different body sizes (i.e. the diameter of the throttle slide) - as the size of the throttle slide bore increased, the numbering of the GP carb model number decreased - i.e. 15GP was the smallest size (comparable to the 15TT carb, and actually quite rare to find), 10GP (comparable to 10TT carbs, and fitted to the later Longstroke Featherbed Manx Nortons - I think 1952-53?), then 5GP, then 3GP.  The range of inlet tract bore sizes for these GP variants is shown below:

15GP Carb:     7/8" To 1 & 1/16"

10GP Carb:     1 & 1/16" To 1 & 7/32" (Replaced the RN carb on late Longstroke Manx Nortons @1952/53)

5GP Carb:     1 & 7/32" To 1 & 3/8"   (Used on most short stroke DOHC Manx Nortons)

3GP Carb:     1 & 3/8" To 1 & 1/2"

The accompanyning photograph shows a line up of 4 racing carb types - a 10TT, 10GP, 5GP and 3 GP, to show the different carb type bodies - with the model this needle is to fit ringed in RED.

The GP carburettor design was an improvement on the earlier TT and RN carb design, in that it had the needle to one side of the throttle body, and fuel enters the choke through a spray tube inclined to one side, rather than from directly underneath as on earlier designs - giving the shortest flow.

To go with this, and to give a more sensitive tuning control - each GP carburettor type had two types of throttle needle available, with a different taper - the 'Normal' type was identified by just having the model type stamped on it - i.e 'GP', or the 'Weak' type which was identified by having a '6' after the model number, i.e. 'GP6'.

Both the 15GP and the 10 GP used a needle stamped just 'GP' or 'GP6', while later 5GP and 3GP type carbs had a needle with that number on it (and a corresponding Weak needle followed by a 6 after the number).

A good starting point when setting up a carb is to look at which of the two needle types was originally fitted for your model - but as so many factors can vary the performance of an individual engine (i.e. fuel used/atmospheric conditions/condition and tuning of engine) - it is often prudent to obtain one of each type of needle and satisfy yourself which runs best (using the original Amal GP setting up instructions).

 

This is a throttle needle to fit original Amal Type 3GP Racing Type carburettors. This is the 'Weak'' type needle (identified by a '6' after the number), but we can also supply the alternate 'Normal' type - See listing for more detail - for that, see Item 1144.

Price is Each

Note - these needes are UK manufactured by a specialist carburettor engineer, to the original Amal needle dimensions.  As per originals, they are stamped with the GP model and type designate (as GP needles were specific to the GP size type and were available in two types - 'Normal' or 'Weak').

I believe this large 3GP version of the GP carb was fitted to later Shortstroke Manx DOHC models (although the even larger Amal GP2 was fitted in the last year of production)

  

Background for GP Carbs:

The GP carburettor was introduced in the early 1950's and was available in a number of different body sizes (i.e. the diameter of the throttle slide) - as the size of the throttle slide bore increased, the numbering of the GP carb model number decreased - i.e. 15GP was the smallest size (comparable to the 15TT carb, and actually quite rare to find), 10GP (comparable to 10TT carbs, and fitted to the later Longstroke Featherbed Manx Nortons - I think 1952-53?), then 5GP, then 3GP.  The range of inlet tract bore sizes for these GP variants is shown below:

15GP Carb:     7/8" To 1 & 1/16"

10GP Carb:     1 & 1/16" To 1 & 7/32" (Replaced the RN carb on late Longstroke Manx Nortons @1952/53)

5GP Carb:     1 & 7/32" To 1 & 3/8"   (Used on most short stroke DOHC Manx Nortons)

3GP Carb:     1 & 3/8" To 1 & 1/2"

The accompanyning photograph shows a line up of 4 racing carb types - a 10TT, 10GP, 5GP and 3 GP, to show the different carb type bodies - with the model this needle is to fit ringed in RED.

The GP carburettor design was an improvement on the earlier TT and RN carb design, in that it had the needle to one side of the throttle body, and fuel enters the choke through a spray tube inclined to one side, rather than from directly underneath as on earlier designs - giving the shortest flow.

To go with this, and to give a more sensitive tuning control - each GP carburettor type had two types of throttle needle available, with a different taper - the 'Normal' type was identified by just having the model type stamped on it - i.e 'GP', or the 'Weak' type which was identified by having a '6' after the model number, i.e. 'GP6'.

Both the 15GP and the 10 GP used a needle stamped just 'GP' or 'GP6', while later 5GP and 3GP type carbs had a needle with that number on it (and a corresponding Weak needle followed by a 6 after the number).

A good starting point when setting up a carb is to look at which of the two needle types was originally fitted for your model - but as so many factors can vary the performance of an individual engine (i.e. fuel used/atmospheric conditions/condition and tuning of engine) - it is often prudent to obtain one of each type of needle and satisfy yourself which runs best (using the original Amal GP setting up instructions).

 

6 part air adjuster kit to fit original Amal TT, RN and GP competition carburetters, containing the following parts: - Air cable adjuster and locknut - Air barrel top - Air valve and nipple holder for air valve - Air valve spring.  CNC manufactured (in stainless steel for top pieces, and brass for slide and barrel) to the original design - including the very distinctive top adjuster and screw in piece, where we have replicated the knurl and chamfers exactly as the 1940 originals - so they also look very pretty.  Kit is six pieces and will fit all Amal TT and RN carburettors and should also fit most later GP carbs).

AUG 2023: NOW BACK IN STOCK 

All parts are CNC manufactured with the same dimensions and profile as the originals, including the distinctive profile/knurl of the cable adjuster kit (3 parts) that screws into the top of the carburettor body - these were quite distinctive adjusters, with a flat top face above the knurl - only fitted to the racing carburettors.  Slide and and slide stop are in brass, but we manufacture the screw in top/adjuster and adjuster locknut in stainless steel - which looks nice and does not rust.

Our screw in top and adjuster locknut use the correct imperial Across Flats hex dimensions, so they fit correct imperial spanners.

Update April 2020:  These are now back in stock.  We are also offering the spring (Item 0850) and the top cable adjuster and locknut (Item 0871) as seperate items.  

Air Adjuster Mechanism - Background:

The air adjuster slide mechanism was fitted to all competition TT, RN (Remote Needle) and later GP carburettors.  There may have been very minor differences to the adjusters over the years (by batch) - but the distinctive overall shape and mechanism - as far as I am aware, remained unchanged. The final two diagrams are original period pictures of a TT carb body with air adjuster mechanism and a cutaway picture of the mechanism as it was fitted to later GP carbs.

The mechanism was not considered a 'Choke' in the way that other carburettors use a choke just for starting - instead it was described as an air adjuster, that would allow for slight richening of mixture by closing - for varying 'atmospheric conditions' or starting.

Because the cable adjuster often used to corrode and get stuck in the hex screw top - it is very common to find someone has loosened it with a pair of pliers(!) - which invariably crushes the original brass adjuster, or at the very least ruins the knurl.  This kit will help restore the original look, as well being less likely to crush in the future - as the cable adjuster is in a harder material. 

It also seemed to be common practice for the air adjuster mechanism to be removed back when these carburettors were being used in period.  Not entirely sure why this was - but I think it was possibly because if they inadvertently closed in a race (through engine vibration or whatever), it could affect carburation and possibly cost someone a race.  I remember when historic racing in the 1980's, it was common to remove this mechanism if fitted.  Because of this, these air adjuster mechanisms have always been hard to find - it is rare to find a second hand carburettor sold with this still in place - so this kit will help replace the full mechanism if missing.

Final point - the original Amal tuning guide for competition carburettors did suggest using this mechanism as an aide for setting up the carburettor - it helping to determine the correct slide cutaway required (as opening closing the slide will help richen the mixture slightly).  We sell a facsimile of the setup instructions in our catalog section. 

These are genuine (old stock) Amal Racing Type main jets - of the type originally supplied for Amal TT/RN/GP racing carburettors.

They are easily identifiable as being the original racing Amal TT/RN type - because the hex part of the jet is uninterupted along its entire length, while the more common later Amal main jets (fitted to all road and competition carbs) had an indented section 2/3 along the jet, which is where the size is stamped.

On these earlier racing jets the main jet size is stamped in slightly larger numerals along one edge of the hex, as can be seen in the accompanyning photographs.  Many of these jets are in the much larger sizes only fitted to racing carbs.  It should be noted, that the later indented type can be fitted to Amal TT, RN and GP carburettors (and jet size should be the same calibration for both) - but out of preference, many people like to fit these original racing jets if available 

As well as the original TT/RN (straight hex) jets, in the same collection were a number of original Amal main jets of the later 'indented hex' design, which were manufactured later for all carb types - including Monobloc and Concentric.  These jets are original Amal (I would between 30 - 50 years old), but similar to the type available new today which we also sell - Item 0153.  Again, the table below shows this 3rd type of original Amal jet (0901_3) - state which size when ordering. All jets of this type are interchangeable with the original 'straight hex' racing type, and there are actually some very small sizes - going down to a very small 050 size.

 

Price is for a single jet, please state which size you require in the comment section when placing order. 

 

We have sub-divided the jets into 3 types:

0901_1 : Original RN/TT 'Straight hex' type: Size from 280 - 640 (mainly petrol)

0901_2 : Original RN/TT 'Straight hex' type: Size from 650 - 1900 (mainly alchohol/methanol. 

0901_3 : Original later Amal 'Indented hex' type: Various Sizes - see table below.  

The larger TT/RN jets are slightly more expensive due to their rarity.  

A Table of all available jet sizes is shown at the bottom of this listing (but apologies if not not kept fully up to date as jets sell).

Background on these jets:  A short time ago I was fortunate to be offered this large collection of original main jets from an ex-racer who was clearly serious about setting his carburettors up correctly (I know he raced both Manx and Gold Star models) - as the collecton was kept in a large box, split into sub-sections by jet size, ranging from approximately 280 up to the largest methanol/alchohol sizes.

All jets are in good original, unmolested condition - and some have clearly never been fitted (i.e. New Old Stock), because they still have the original wire/lead spot they were supplied with when new.  

If you are setting up a TT, RN or GP carburettor it is always a good idea to keep a selection of jets of various sizes - so that you can vary the jetting, to get the ideal jet for your state of tune/fuel.  Doing any form of engine tuning, changing fuel (or even ambient track temperature on a finely tuned engine) can make a difference.  If you are not sure how to tune your Amal racing carburettor for the correct Main Jet/Needle Jet/Slide/Needle settings, then in our Facsimile/Catalog section we offer a facsimile that includes original Amal information how to do this.

As a general rule of thumb - I have found that most competition bikes using Amal TT/RN on petrol tend to use main jet sizes up to a @ 650 main jet (dependent on cc/state of tune), while those bikes running on methanol or alchohol use much bigger jets from 550 all the way up to a (massive) 1900.  These original larger jets are now very uncommon to find - and once these are gone I doubt I will be offering any more!

Table of Jet Sizes Available:

Item	Description	Jet Size	No in Stock
0901_1	Original Amal TT/RN Type (350-640)	350	1
		370	1
		380	1
		410	4
		420	2
		430	2
		450	4
		460	4
		470	4
		480	4
		490	4
		500	4
		510	4
		520	4
		530	4
		540	4
		550	4
		560	4
		570	4
		580	4
		590	4
		600	4
		610	4
		620	4
		630	4
		640	4
0901_2	Original Amal TT/RN Type (650-1900)	650	4
		660	4
		670	4
		680	4
		690	4
		700	3
		720	3
		740	3
		750	3
		760	3
		780	3
		800	3
		900	4
		910	1
		920	4
		940	4
		950	3
		960	4
		980	4
		1000	4
		1050	2
		1100	3
		1200	3
		1300	3
		1400	4
		1500	4
		1600	4
		1700	3
		1800	1
	(this size avail in indented - see below)	1900
0901_3	Original Amal - later 'indented' type.  All sizes	50	1
		55	1
		150	1
		190	1
		210	1
		260	2
		270	1
		290	1
		300	1
		310	3
		320	2
		330	1
		340	1
		350	1
		360	3
		390	2
		400	1
		420	1
		450	1
	(alchohol jet - but later indented type - fits TT)	1100	1
	(alchohol jet - but later indented type - fits TT)	1200	1
	(alchohol jet - but later indented type - fits TT)	1700	1
	(alchohol jet - but later indented type - fits TT)	1900	1

 

Useful little box key spanner for fitting and unfitting main jets on most Amal carbs that used the standard type Amal Main Jets (as shown in photo).

Nice quality and very useful to keep in your toolkit . . . saves trying to find a spanner to fit!!

- Hexagon Lockscrews that fit in the top of the large Type 302 Floatchamber - This is the larger competition floatchamber fitted to Gardengate Manx Nortons (fixed version) and later Featerhbed (Remote version) Manx Nortons - These are high quality hex screws with holes for lockwiring, just as originally fitted. Price is for each

4 part tickler kit to fit original Amal 302 Floatchambers - as fitted to Amal RN and GP carbs from the late 1940's through to the early 1960's.  This float tickler design is very similar to the type fitted to most Amal 276/289, TT, and RN floatchambers - but for this larger capacity racing Type 302 type floatchamber - a longer shaft was required, as the tops were quite different. As with the other type we supply to fit standard floatchambers (Item 0162), an original Amal Type 302 float tickler was used as a pattern, and our components match the originals exactly, and are CNC machined.

As can be seen from the photos, these tickler kits consist of the tickler pin, a small lock ring (which fits under the float chamber lid - and again is to the original design, a tickler spring and a split pin.  An original Type 302 Floatchamber tickler assembly was used as the pattern for our items, which are CNC manufactured in brass, then satin nickel platerd, as per originals.  This longer type of tickler design is now very hard to find and often missing or worn in original flaot chambers.

In case you are not sure if your floatchamber tickler is of this 302 type - the overall length of the tickler shaft is 32.4mm, while the standard tickler shaft (our item 0162) is 27.7mm 

Note - we also manufacture a similar tickler set to fit standard design and size float chambers (i.e. Type 276/289, TT and early RN carbs), which has a shorter tickler shaft - See Item 0162

This is a cable adjuster and locknut with a 0.250" BSC thread, which is of the distinctive 'knurled' type that were originally fitted to Amal TT, RN and GP competition type Air Slides - however, they can also be used as throttle cable adjusters on other carb types - that had a similar thread, or a 1/4" through hole to take a similar adjuster. 

Price is per adjuster and nut.

These are CNC manufactured from stainless steel with the distinctive flat top face above the knurl - only fitted to the racing carburettors.  Locknut uses the correct imperial across flats dimension as the original (originals being used as the template for these).

This cable adjuster (and indeed the complete air adjuster mechanism) was often removed from Amal competition carbs in period.  If they are still in place it is very common for someone to have tried to unlock them with pliers - as the originals were plated brass - this almost always crushed the top cable recess or ruined the knurl.  Therefore, these adjusters with the correct profile are now very hard to find in good condtion - our adjusters are therefore a nice detail touch!  We sell the complete TT/RN/GP air slide kit - whiich includeds this threaded adjuster and locknut as Item 0149, however, some customers may already have the other parts - and as it is this adjuster that commonly gets 'mauled' most commonly, we also sell this adjuster and locknut seperately here.

Fitment to later TT Carbs and other carbs and Twistgrip Throttle Assemblies:

This particular type of adjuster was always fitted to the TT/RN (and GP) Air Slide cable top piece - it having a 0.250" BSC Thread.  Most earlier Amal TT and RN carburettors (approximately up to 1952) used a different (larger - 3/8" BSC thread) adjuster for the throttle cable and Top Cap - we also sell that item - Item 0874).

Later TT and GP carburettors often had a Top Cap to take a much slimmer throttle cable adjuster, similar to that used on the roadgoing Amal Monobloc and Concentric carburettors - that type was of lesser diameter than the adjuster shown here - but we sell that type of adjuster as well - Item 0149.

However, you may find that some Amal TT Top Caps have a 'through hole' - which may be of 0.250" diameter (I have seen numerous patterns fitted over the years to these carbs) - in whcih case this could be a suitable altenative.

Twistgrip Throttles: (i.e. genuine Doherty Type):   It should be noted that most genuine Doherty Twistgrips (including the modern genuine Doherty twistgrip we sell - Item 0942) did not have provision for a cable adjuster to be 'screwed in' to the handlebar casting - instead they had an 'unthreaded' hole - which might have had a ferrule or an adjuster dropped into that hole in period.  We manufacture a stainless steel 'Top Hat' Ferrule for this type of Doherty Twistgrip - see Item 1178, but as can be seen in the accompanyning photographs of both a genuine original Doherty quick action twistgrip, and a modern Doherty twistgrip (Item 0942) - the knurled adjuster and locknut offered here is also a viable alternative to be used with a throttle cable on the Doherty type twistgrips of that type - as the 0.250" diameter adjuster is a perfect 'drop fit' into the hole, and where the locknut is used to adjust the final tension of the cable (and being stainless steel, they are less likely to rust in the elements).

 

- Banjo to fit TT and RN competition carburettors