This is a replacement for Amal TT or RN bellmouth if you want to use the bike on the road and are concerned about ingestion of dirt or grit - which some people are, as the standard Amal TT/RN type bellmouth is open to the elements.

The inlet is CNC machined from the same alloy billets as the 'Short TT Bellmouth' (Item 0140A) we also offer, but in the case of this type - the outer curved lip of the original bellmouth is changed to a flange, allowing snug fit of a cone type filter.

The cone is a commercially available 'Pit Bike' filter with  .  It has a 'standard' short type TT/RN inlet tract and thread with a modern 'Pit Bike' cone type filter fitted.  In some of the attached photographs the chrome of the cone filter looks blue - this is the plastic protective film supplied with the cones to protect the chrome and should be peeled off after fitting.   

These are CNC machined and are available in two bore sizes: Standard Norton International 500cc size - 1 5/32", and also 1 3/16" bore size (which is another popular size in our normal TT/RN bellmouth range) and the largest normal bore size that original Amal TT and RN carbs were supplied with). State which size you require in the comments section when ordering.

FYI - I would expect that the bore size is far less critical on this type of bellmouth, i.e. in case you have a slightly smaller bore size, such as 1 3/32" etc. - Normally the bellmouths on Amal TT (and other competition) carbs were blended with the carb size exactly - to assure maximum efficiency at maximum racing speeds.  For those fitting this type of bellmouth/filter . . . normally on the road, to offer some engine protection from grit etc - you should expect that this carb setup is no longer going to be suitable for maximum competition performance (and a level of re-jetting may be necessary anyway)

It should be noted that these filters (as fitted to pit bikes) look to be of the gauze and thin filer material type, and although good value - they are not the K&N washable paper filter type - which would make the unit far more expensive.  However, if you wish to fit a K&N style filter yourself at a later stage - then I believe the RC-790 K&N Model is a likely fit (email to confirm details of bore  etc if you are considering this) and should have the same fittings. Note though - when I checked retail prices of this model of filter in the UK, as part of making these units - I found the price of the filter alone in excess of the retail price of the entire unit shown here.

Fitting Instructions and Jetting:

Just as with normal bellmouths to fit original Amal TT or RN carbs, these bellmouths have a thread that screws into the main body and will also use the standard TT/RN lockring (so you should be able to use the one from your existing bellmouth, or we can supply seperately - Item 0142).

It goes without saying that - just as you would when fitting any original Amal TT or RN carburettor to your motorcycle for the first time - if fitting one of these filters, you should check the settings yourself to confirm if re-jetting is required (i.e. Main Jet or Pilot Jet) - as this can vary a great deal from one engine to another, and is also dependent on the condition of the original carburettor.  We recommend following the normal procedure for tuning an Amal TT or RN carb to satisfy yourself it is correct - and re-jet as necessary.  If you do not feel you have necessary experience or would not want to do this - then we recommend not purchasing this item and continue instead with the original open bellmouth

- Lock ring to fit original Amal 10TT, RN and some GP carburettor bellmouths.  These alloy lockrings are CNC machined copying an original Amal TT pattern for reference.  

- These lockrings are intended to fit Amal competition carburettors and help lock the bellmouth in place. On post-war TT carbs, it serves a dual purpose of locking the cap ring retainer spring.  They have a 1.5" diameter internal thread and were fitted to all 10TT and RN10 carburettors as well as GP carburettors with the same bellmouth outer diameter

- These - Helpful hint : to correctly fit these, buy a Girling shock absorber adjuster C-Ring spanner, then file the tang on the smaller C, it will be the perfect tool for locking these without damage to the ring

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. 

This listing is for the distiinctive shouldered and profiled hex head bolt that fitted to the Inlet ring on Amal Type 76/276 and Type 86/286 Stub Fitting Carburettors - it having the important function of ensuring the carb was securly located to the inlet stub.  These are CNC manufactured by us to the original design in stainless steel and the heads lightly polished.

They were also used on Competition TT/RN clip fitting carburettors.

Price is each.

We have replicated the original design of this small bolt - which as you can see in the photos - has a distinctive grooved shoulder - so that the actual hex of the bolt is held out from the inlet clip - to allow for the best possible tightening with a ring spanner.  This small detail may seem incongrous - but when you realise that it is this bolt that correctly tightens the whole carburettor to the inlet stub - and that on many motorcycles, the head of this bolt was not easy to get good spanner access to - it makes you realise how important a job it has to do!

Because of this difficutl access, and because of the engine vibration and weight of the carb - it is not uncommon to find that the ''Stub' fitting type carburettors often have this orignal bolt badly 'chewed' and the hex faces badly rounded.  This of course means the carb is far more likely to not get fully tightened - often leading to wear of the carb bore, and meaning air can enter from the stub and affect the running of the engine.

As well as the distinctive sthape and profile of the bolt - we CNC mill the hex head to the correct imperial spanner size of  1/8" Whit (we mill this head, as it is becoming increasingly difficult to obtain it in stainless steel), which gives a very crisp finish - important, as it is often this hex head that suffers on original carbs - as they are often overtightened with use.   We emphasize this - because having personally experienced the annoyance at having to try and continually tighten an original bolt, where years of abuse has 'Rounded' the original head of a Type 276 carb, it is a pleasure to fit a bolt that allows a close fit of the correct spanner!

As a final design point - we have also replicated the opposite threaded end on these small bolts - which was rounded, as it protruded from the threaded end of the ring - presumably to avoid it catching on cloth's when the owner cleaned the bike.

- Full washer kit to fit original Amal TT and RN carburettors 

This set consists of flange brown paper washer (generic diameter), two washers for jet block body (the black and smaller fibre washer) and 4 washers to fit the banjo's used on TT and Amal RN carbs.

Note; some TT carbs do not require all 4 of the larger banjo washers - but our kits come with four, so they will fit those carbs using a seperate banjo on the floatchamber, as well as the banjo of the float fitting to the main carb body jet holder.

(note dependent on batch, sometimes the banjo washers are all four of the same type, while other kits have two sets of 2 slightly different washers - but for both types the banjo washers are high quality and all fit the banjo seal exactly), see first and second photos.

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).

2 part throttle cable adjuster and locknut to fit original Amal TT and RN competition carburetters (with 3/8" diameter BSC thread), CNC manufactured in stainless steel, but with the same profile and distinctive knurl as the original competition item. 

Price is per Adjuster and Locknut

These are CNC manufactured from stainless steel with the distinctive flat top face above the knurl - only fitted to the earlier Amal TT and RN type racing carburettors (up until the early 1950's - later competition carbs being fitted with the more common monoblock road type).  Locknut uses the correct imperial across flats dimension as the original (originals being used as the template for these).

This cable adjuster was fitted mainly to the earlier (pre mid 50's at a guess) original Ama TT and RN carb tops.  Originally they were were manufactured in brass and dull nickel plated, and were fitted with 3/8" diameter BSC fine thread cable adjuster.  An original adjuster and locknut is shown in the second photograph alongside our version, and was used as a template.  However, because they were made in brass - they were often 'mauled' with pliers and it is now very rare to find this original and distinctive design still in good condition.

It should also be noted that this original type of threaded adjuster was also counterbored underneath to fit the early type straight throttle spring, as shown in the second photograph.  Our versions have the same counterbore.  We also sell both the parrallel type spring and the later conical type spring . . . bot types can be used with this adjuster if required.  

The original adjuster was in brass and very often seized in the carb top .  .. and then owners tried to remove them - invariably with a pair of pliers - so it is normal to find carbs missing these adjusters, or at least with the knurl chewed or crushed.  Our versions are CNC manufactured in stainless steel, so as well as looking nice, will be stronger than the brass originals.

Final point - later alloy top caps (probably mid 1950's onwards) were often fitted with smaller inner diameter alloy caps - and sometimes smaller adjusters, or no thread in them at all.  For this later type of cap - see the later adjuster we also offer - Item 0145, later in this section.

We CNC manufacture these in stainless steel to the original design so they do not rust and will add the final touch to your competition carb restoration - but although small they still require multiple machining ops (including the slim nut which requires a special 2nd op to remove scurf after parting), hence the price.

This listing is for a universal type throttle cable of 37^ in length, with nipples fitted either end - to fit most twistgrips and Amal carburettors.  This cable type has an adjuster in the middle of the cable (about 6" below the twistgrip). 

Price is Each.

This cable type comes with a small barrel type on one end (of the type that fits in all the twistgrips we sell), then a cable adjuster and locknut about 6" further along the cable (i.e. ideal for being adjusted when sat on the bike, just below the handlebars), and with a small cylinder ferrule at the other end - of the type that will fit most Amal throttle slides (including TT, RN and GP).

It should be pointed out though that if you are making cables up for competition TT, RN or GP carbs - and are intending to use our 'original type' air adjuster kits or throttle cable adjusters - that fit into the body of the carburettors - then you will need to unsolder the barrel at one end, carefully grind the cable to a point - so the barrel can be removed, then the outer cable adjusted to account for an new adjuster that is fitted.

We also sell a spare throttle cable outer cable ferrule, and inner cable barrel ferrule (i.e. the twistgrip end) as a seperate item - Item 1218, so if you are modifying the cable, and do not have a box of ferrules . . . you can fit a new outer cable ferrule if you have trimmed this cable to length, and fit a new inner cable barrel if the one that comes fitted is unusable (see Item 1218 for more information)

Although not listed - I should also be able to help with extra ferrules and cable barrels - and may be offering them in the near future (this update in January 2024). Also, if you email me on paul.norman@racingvincent.co.uk, I can provide more information on this cable setup process - it used to be a normal part of any 'Project Build' - making up all the cables to fit your particular motorcycle - but if you are doing this yourself for the first time - remember to 'tin' the cable before cutting or grinding it, and use plumbers solder rather than electrical solder.

This listing is for a universal type throttle cable of 37^ in length, with nipples fitted either end - to fit most twistgrips and Amal carburettors.  This is the 'plain' cable type - i.e. there is no adjuster fitted along the cable length.  

Price is Each.

This cable type is useful if you are fitting it to a carburettor or twistgrip that has its own cable adjuster already fitted.

In the case of twistgrips - some twistgrips come with a cable adjuster which is 'slotted' along its length - in this case, you may find the cable can be used just as it is (i.e. it comes with the ferrules either end already fitted, to fit most twistgrips and Amal throttle slides) - as the inner cable can be fed through the slot, without having to remove an inner cable ferrule to slide it on.

However, the main reason we list this type of cable, is for those customers who are fitting an Amal competition carburettor such as the Amal TT or Amal RN (for which we sell many parts, including - the original type cable adjusters particular to those models) - and want to fit cable adjusters particular to that carburettor type - either throttle cable, or air slide cable.  In this case - of course it will be necessary to heat one cable end up, to release one of the ferrules, and then feed the required adjuster on to the cable - and probably require the outer cable cutting to length, before re-soldering.  To do this it is expected you will be familiar on how to 'make up' cables yourself (i.e. tinning the inner cable, how to grind the end without fraying the strands etc) - but if you need help with this, you can email me at: paul.norman@racingvincent.co.uk.

We also sell a similar length throttle cable with a cable adjuster fitted midlength - this is Item 1216.  It should be noted though that that cable has a 'top hat' type outer cable ferrule on one end, which means it can be dropped into a carburettor top with no thread - while this cable type has a plain outer cable ferrule at both ends (i.e. it will just drop through a carburettor top, if the top was intended for a cable adjuster.

As a final note on this - if taking this route (i.e. removing the ferrule from one end to fit an adjuster etc) - we can also offer a useful small item -  Item 1218 - which consists of a spare throttle cable ferrule - of the type commonly fitted at the twistgrip end, and one outer cable ferrule, which can be fitted over the end of this outer cable, if you have trimmed it to a new length (I normally use a small sharp punch, to slightly punch the ferrule after fitting over the cable outer, to stop it coming off).

Also, if making up cables for yourself for the first time - remember to 'tin' the cable before cutting or grinding it (to help prevent the cable strands splaying), and use plumbers solder rather than electrical solder, as well as a good quality soldering flux.  and FYI - do not put any oil on the inner cable where you are intending to solder - they almost never 'tin' once impregnated wtih oil.

This listing is for a spare Throttle Cable (or choke/air/magneto type cable) outer cable ferrule, and a spare inner cable barrel of the type normally fitted on the twistgrip end of throttle cables. 

This item is useful if you have bought a throttle cable (see items 1216 and 1217) and need to then cut the cable to length or fit an adjuster.  

Normally to amend the length of a cable, or fit an adjuster, requires that the outer cable has to be trimmed to a new length - which loses the pressed on cable end ferrule that it comes with.  Therefore this spare outer cable ferrule can be placed over the newly trimmed outer cable to protect it.  When making up cables - I normally use a small sharp punch and give this ferrule a small punch midway along its length, to stop it slipping off in use.

Likewise, the inner cable barrel ferrule can be used to replace the twistgrip end ferrule, if the original is not re-usable after amending the cable.  But make sure you check this barrel type fits your twistgrip (or air/magneto lever, if being used for that purpose) before fitting!

You can email me on paul.norman@racingvincent.co.uk if you require more information about making up and soldering your own cables - or require other ferrule types, I may be stocking more types in the future.  Also - read the listings for Items 1216 and 1217 for more information.