This is the valve retaining collar of the type fitted to Douglas 2 3/4hp models, used to retain the valve springs by means of this collar and a steel pin that fitted through a hole at the end of the valve.  The collar is CNC manufactured from EN24T to the original design - which means there is a central rececss to hold the silver steel pin captive, but the collar can revolve around the valve stem.

The collar is CNC manufactured from hard wearing EN24T

Note:  I am told this was the original design specification for these collars for the Douglas 2 3/4hp, therefore this item is made as per that design.  However, we also offer a modified design of this collar and pin (Item 0729), whereby the collar has an additional slot milled in the recess. 

When I originally manufactured these collars, I took the design from an original collar which had a similar slot recess.  I cannot be sure if this was just wear to an original type collar, or if someone had modified that collar - but from an engineering perspective I feel the additional slot is a better solution as it should ensure the pin is more captive, and more importantly stops the collar from spinning around the valve - I have a couple of examples of old valves where there is clearly a wear groove on the top of the valve where this has happened.  I am not an expert on this engine in use, hence I offer both types (however, I am building my own project bike with the modified design, and will report back once the engine is running)

This listing is for the original type - consisting of one collar and one silver steel pin (4 required per engine)

This item is the distinctive long cylindrical exhaust lifter assembly plunger box, that screws into the front of the Douglas 2 3/4hp models and retains the screw in Exhaust Lifter cable adjuster and cable.  Inside the cylinder is the spring that holds the exhaust valve lifter assembly in tension.  This item listing is for the plunger box bolt (CNC manufactured in stainless steel) and spring.

An original exhaust lifter plunger box and spring was used as the template for manufacturing these (these were fitted to a spare 1922'ish Douglas engine I have) and was very useful as all fittings in this engine looked original.  The dimensions of the plunger box bolt have been copied exactly from the original, including the correct thread to allow the unit to be screwed into the crankcase.  The plunger bolt has an internal 1/4" x 26 tpi thread, to allow a cable with standard cable adjuster and locknut - which is the primary means of adjusting the exhaust lifter assembly tension when not acting against the cam followers. 

It is worth noting that the original Douglas plunger unit bolt that screwed into my spare engine crankcase did not have any locknut, and neither does the original Spare Parts List show a locknut - instead it just screwing into the crankcase timing chest, until the correct position attained.  The bore of the plunger box bolt holds the spring, but then the original exhaust lifter mechanism inside the timing case has a plunger (which the exhaust lifter cable screws into, with a special theaded ferrule) which also fits into the bored plunger body - the mechanism then all being held in line inside the plunger body.

I noticed that on the original Douglas plunger bolt fitted to this spare engine, that the plunger body - being very thin bore by design, was completely worn through on one side, with the spring visible.  Although this wear would be inevitable after heavy use, and would still allow operation unless a large amount of the 'tube' bore had worn away, it may be worth checking your original plunger body if you have this model, to check how badly worn your original is.

The plunger box bolt is CNC manufactured in stainless steel and had the correct thread and Imperial hex spanner size as the original item.  The spring is also replicated from the original Douglas spring dimensions - this being of a stronger gauge than most springs this size and barreled at both ends - which makes a difference when fitted, the exhaust lever on the handlebars requires a nice pressure to operate.  We have had a batch of these springs made by our trusted UK spring manufacturer and they are also available seperately (Item 0992)

Finally, for anyone restoring one of these models, and not having the full assembly to refer to - I have included a few of the photos of how the Exhaust Lifter cable and adjuster mechanism was assembled, including a picture of the distinctive bent shaft with barrel shape at one end, that is designed to slide inside the sleeve bolt, acting against the spring inside it.  The other end of this rod has a sideways pin, that attachs to the exhaust lifter lever assembly in the timing case.  The sideways pin on this special rod initially looks like it is too long to allow the rod to be fed through the threaded hole of the timing case (once it has been assembled onto the exhaust lifter cable and assembly - but if you look carefully in one of the forward facing photos of the crankcase, you will notice there is small notch placed in the Douglas exhaust lifter hole in the crankcase for this purpose. 

At the 'barrel' end of the rod is hole that is threaded internally (with a 3/16" BSW thread I believe), so it can accept a lightweight cable, which has an unusual threaded nipple.  As the photographs show, I manufactured one of these from a small 3/16" BSW bolt, drilling it approximately 55 thou so the lightweight cable inner could be fed through the threaded area and belled out at the end and soldered.  I hope this may help for anyone restoring or overhauling this assembly in the future.

This item is the barrel shaped spring that was fitted to the Douglas 2 3/4hp exhaust lifter assembly, where it feeds into the plunger bolt.  We also sell the plunger bolt as a kit (Item 0975) - but this listing is for spring only

An original exhaust lifter plunger box and spring was used as the template for manufacturing these (these were fitted to a spare 1922'ish Douglas engine I have) and was very useful as all fittings in this engine looked original.  The dimensions of the plunger box bolt have been copied exactly from the original, including the correct thread to allow the unit to be screwed into the crankcase.  The plunger bolt has an internal 1/4" x 26 tpi thread, to allow a cable with standard cable adjuster and locknut - which is the primary means of adjusting the exhaust lifter assembly tension when not acting against the cam followers. 

It is worth noting that the original Douglas plunger unit bolt that screwed into my spare engine crankcase did not have any locknut, and neither does the original Spare Parts List show a locknut - instead it just screwing into the crankcase timing chest, until the correct position attained.  The bore of the plunger box bolt holds the spring, but then the original exhaust lifter mechanism inside the timing case has a plunger (which the exhaust lifter cable screws into, with a special theaded ferrule) which also fits into the bored plunger body - the mechanism then all being held in line inside the plunger body.

I noticed that on the original Douglas plunger bolt fitted to this spare engine, that the plunger body - being very thin bore by design, was completely worn through on one side, with the spring visible.  Although this wear would be inevitable after heavy use, and would still allow operation unless a large amount of the 'tube' bore had worn away, it may be worth checking your original plunger body if you have this model, to check how badly worn your original is.

The plunger box bolt is CNC manufactured in stainless steel and had the correct thread and Imperial hex spanner size as the original item.  The spring is included and UK manufactured by my main spring manufacturer to an original Douglas pattern

If you have looked at this listing before (i.e. prior to October 2021) you will have seen that we were able to offer a modern reproduction of the original spec KLG ML50 - which had the correct (and now very difficult to find) 18mm 'Long Type' thread, which was 0.750" in length, as was originally fitted to some Norton models (i.e. WD16H Norton and the early Douglas 2 34hp and 3.5hp models).  Unfortunately, these have now all sold and our manufacturer supplier tells us that (partly due to Covid impact) they are not likely to have another batch made, so are now unavailable - sorry.

However, having talked to this spark plug specialist, I am told that there are modern 18mm 'Short Length' spark plugs available (i.e. 0.5" length thread), and these will still work in a cylinder head with 0.750" thread length - and in fact it was quite common for this length plug to be fitted even in period times.  Therefore, we now offer two modern Champion alternatives in this listing - both in 0.5" thread length and will continue to add if other types come available.

We are also looking at the possibility of converting a quantity of 'New Old Stock' KLG WW2 18mm WD aircraft spark plugs (with 0.750" threads) to a suitable motorcycle spec - as they currently have the aircraft style suppression tops.  Email us on sales@racingvincent.co.uk, if interested, we will update this listing at a later date if successful  

Finally, this listing also offers both 14mm and 18mm modern copper/asbestos type crushable washers for spark plugs

Spark Plug Types:

0896_5 Champion D14 - 0.5" Thread Length.  Normal Running for Side Valve Engines:

These are modern 18mm 0.5" reach plugs, made by reputable manufacturer Champion - and the D14 variant is considered the best choice of grades for a Side Valve engine in normal running condition. As 0.750" reach plugs are now unobtainable - these provide a suitable alternative, and according to our supplier - were often fitted to those engines with an 0.750" length spark plug hole even in period times.  

0896_6 Champion D16 - 0.5" Thread Length.  Oily or Rich Running for Side Valve Engines:

These are modern 18mm 0.5" reach plugs, made by reputable manufacturer Champion - and the D16 variant is considered the best choice of grades for a Side Valve engine if your engine runs rich or often oils plugs. As 0.750" reach plugs are now unobtainable - these provide a suitable alternative, and according to our supplier - were often fitted to those engines with an 0.750" length spark plug hole even in period times.  

 For the two plug types above (the same type of plug - but with a fractionally different heat settings - it may be prudent to take one of each type and find which is best for your own engine, if you are not sure which you require.

0896_1 KLG ML50 - 0.75" Thread Length. (Sorry now unobtainable):

For anyone that has searched for the 'Long Reach' (0.750") type 18mm plugs that were fitted to some older (pre-WWII) motorcycles or cars, they will know this longer reach type are now extremely hard to find - most 18mm types now available being a shorter 0.5" inch length - which although can be fitted, can upset the combustion and timing slightly. This type of long reach 18mm plug was of the type fitted to both Douglas 2 3/4hp models (if fitted with 18mm plugs) and some early Norton single cylinder models.   I know this type was fitted to Norton WD16H models - and in the accompanying photographs you can see one of these plugs fitted to an original 1938 manufactured Norton WD16H cylinder head.  I do not have any other earlier Norton 18mm heads myself - but would expect this type of 18mm/0.750" spark plug hole was likely to have been used on earlier Side Valve models and maybe some 1920’s OHV models? . . I expect if you own of these you will know yourself if it requires this type of plug.

Update September 2021 - Very sorry, but our suppliier has now ran out of this plug - and is not expecting to have another batch manufactured (partly due to cost increases post Covid).  I have kept the listing here, in case this changes in the future - and will update it if a new batch are to be manufactured in the future

0896_7 KLG RML 60 - 0.75" Thread Length. (Oct 2021 Enquiry Only - but possible special order):

As at October 2021 - we are looking at the option of converting a quantity of 'New Old Stock' WW2 military aircraft KLG spark plugs - which also have the longer 0.750" length spark plug thread, as fitted to the models described above.  As can be seen in the photograph - as originally manufactured they have a special 'aircraft type' suppressor fitting - and will not accept a standard motor cycle style HT Cap.  We are currently looking at re-manufacturing the top of these to fit a motor vehicle style insulator and central core, so they will accept a standard HT Cap or screw on knurled top.  If interested - please email sales@racingvincent.co.uk - but expect the price to reflect the work required to re-manufacture these, and their rarity

0896_2/3/4 - Crushable Spark Plug Washers:

If like me, you have numerous 'New Old Stock' spark plugs - but they have lost their original 'copper/asbestos' type washer (with the distinctive copper colour), we can now supply them in both 14mm and 18mm sizes - in packs of six.  The 18mm size have two thicknesses - the wider type being slightly more expensive (and sold as a pair) - but the slimmer 18mm type are still usable and worth keeping some in your toolbox in case you lose one on a run.  You would normally replace these washers each time you remove the spark plug (unlike modern steel spark plug washers) – so it is worth keeping some in your toolkit

Note: Originally these heat resistant 'crushable' type washers were copper with asbestos filling - these modern ones no longer use asbestos - but instead a modern safer filling!

If we find any other modern reproductions of the older style veteran 18mm or 14mm plugs we will add them to this listing - please email us on sales@racingvincent.co.uk if you know of anyone manufacturing them, thanks.

This listing shows a selection of brass fittings for veteran motorcycle spark plugs, as well as some rarer spark plugs and fittings (and a nice copy of the Veteran Lodge style brass cooling fins that fit over most spark plug types).  We have manufactured the knurled brass nuts for securing the HT lead on older motorcycles (i.e. pre spark plug cap) in two main styles and a variety of threads.

Note: see also Item Listing 0896 - since originally starting this multi-item listing, I have now listed our 18mm KLG type spark plugs seperately, along with 18mm/14mm copper abestos type spark plug sealing washers.

Spark Plug HT Lead Nipple/Knurled Nut Background:

If you have an older historic motorcycle - i.e. pre WWII or earlier, then you may decide you wish to fit the HT lead to your spark plug with a brass connector, rather than with a more modern HT Spark Plug Cap (of which we also sell in various styles).

Like many old motorcycle enthusiasts, over the years of collecting I have accumulated a selection of old spark plugs of various styles, and some of these go back to the earliest motoring days of the 19'teens - 1920's.  When recently I was looking to fit spark plugs to my own 1919 Douglas 2 3/4hp project bike (used for some of the photos in this listing), I decided to fit period 18mm spark plugs and our ochre coloured cloth/waterproof HT lead, along with veteran style brass HT clip connectors (i.e. pre plug cap) - which would have been correct for a veteran bike.

To go with this I investigated the different style of knurled screw on nuts which were commonly fitted to these early type of plugs, which allow the brass HT connectors to be easily screwed on our taken off.  I was suprised to find there were lots of styles and variations over those early days - but by far the most common type was the knurled adjuster with a design commonly seen fitted to Champion spark plugs.

However, I also have an example of a very pretty Lodge type of knurled nut - which has a wider top knurl diameter and a concave tope.  As well as giving good purchase when tightening the HT lead to the plug - I think this type of knurled is very pretty, and quite rare now.n

Therefore - we have replicated  both these definitive styles - the bigger diameter Lodge type being an almost identical copy of the original nut, while the other small type is copied from an original definitive type used on a 1920's Champion plug (note - I found numerous nuts of this style, many with minor variations over the years - but chose an early type of the most definitive design).

Both knurled nut types are CNC machined in brass by us and can be supplied in a variety of threads - the sub listing items representing the most commonly used spark plug top threads used.  

Early Spark Plug Brass Cooling Fin - based on Lodge original, to fit most spark plug types (0895_8):

As you can see in the first photo, in my spark plug collection I have an unusual and very pretty/rare pink Lodge H1S spark plug (New Old Stock), which has the addition of a brass cooling cap with fins, which sits atop the porcelain.  I have seen similar brass cooling fins fitted to the very earliest (i.e. Edwardian) motorcycles and cars and they give a lovely period look to an older motor vehichle restoration.

We have reproduced this finned cooling ring - to an almost identical profile, but underneath, the ring counterbored so that it will fit on top the porcelain of almost any spark plug - including modern plugs.  By so doing, if you wish, you can use modern spark plugs (with make scrubbed off if required!) and this ring placed on top of the porcelain to give the plug a much older and pretty look. 

We offer this cooling ring, along with the knurled 'Lodge' type HT nut (specify which thread type for nut when ordering)  - as shown in the photos associated with this item - including them having been fitted to the KLG 18mm ML50 plugs we also offer here, fitted to my own Douglas 2 3/4hp project.  I have to say, they nicely finish off this area of the restoration.

Spark Plug Top Thread Background:

Until we came to make these knurled HT nuts, I had always assumed the top thread used to hold the HT nipples on spark plugs was a standard thread - standardised on all spark pluge going back to the earliest days - No such luck!

It turns out there were numerous threads used over the years - and I do not think we have found them all!, however I think we have identified the 4 main types (and two seem most commonly used), and have made the two knurled nut styles in sub-types to take into account the different thread types.

I have also gone through my own spark plug colletion and tried to identify the different Makes and Styles that used the different thread types - I cannot be sure that if you have the same spark plug in your collection, it will have the same thread (as they may have changed by year) - but in the accompanying photographs, I have showed some of the plugs with their various thread type in the sub listing to help you select which one is right for your plug.

If not sure - I would suggest you buy one of each (!) . . . but do not try and force on by more than two threads or the brass may strip.  

I cannot be sure this is definitive - but in general I found the following threads used on the following plugs (see photographs that accompany the individual items):

- 8 UNC Thread (0895_1 and 0895_4):  

  - Champion:  I found a number of the older (or US branded?) Champion plugs fitted with this metric 8 UNC Thread.  Those tried with this thread included: Champion N5 (common 14mm 1960's - 1980's plug/ C5 (22mm plug) - both early 1930's rounded ceramic type and later (1960s style multi ridged type) / J10-COM/ L7 (another 14mm 1960s style plug)/ D8C - this last plug is a rare 18mm long reach plug with an unusual extended 3 prong electrode - they are a possible alternative for Douglas 2 3/4hp engines - but you need to ensure electrodes will not fould valves.  I have a pair of 'New old stock' D8 plugs as the on-bike spares. 

  I suspect as Champion was commonly sold in US, that earlier Champion pluges were predominantly this thread - but not entirely, see below in metric threads.

  - KLG:  FE75 14mm plug (1950s style plug?) 

  - Lodge:  Some Lodge threads were UNC, others were metric.  Three of the pink ceramic Lodge plugs I have in my collection were this 8 UNC thread - CANY plug (common 14mm plug), HL14S (pink ceramic 14mm plug - but with earlier seperate hex component for locking in cermaic and H14S with brass cooling fins fitted (this last plug was the one with the big knurled Lodge nut and cooling fins shown in many of the photographs - that we used as a template for 0895_5)

  - Wipac Pacey: F2.0 - blue ceramic 22mm plug

  - AC :  AC 78 22mm plug, made in the USA.  Note, in the accompanying photograph there is a second very similar plug to this, which is also 8 UNC - but has no marking whatsover.  I think this second plug may be another AC or possibly a Bosche make

  - Autolite: In the accmpanying photograph is a 'new old stock' Autolite A652.  Not a common plug - but I believe a 1960's-80's 14mm long reach plug 

- 4mm x 0.70mm Thread (0895_2 and 0895_5):  

    -  NGK: This looks to be the thread adopted by all modern NGK plugs - in case you want to fit a good quality, easily available, modern (14mm) plug  on your old motorcycle, but still use these knurled brass nuts for a period look.  NGK plugs tried included B6ES (common 14mm long reach, including fitted to many british bikes), B9HC and B77HC

  -  Item 0896_1 KLG Plug: Our 18mm KLG ML50 new plugs (Item 896_1) use this metric thread.  Note; as supplied these plugs come with the normal HT cap modern round nut - so if you want to use a knurled nut, they are with this thread

- Original KLG: KLG FE100 14mm plug, which is 'new old stock' and looks to be of 1950's-60's vintage.  Note: this plug looks very similar in appearance to the FE75 plug above, which is UNC - so it looks like KLG at this period used both thread types!

  - Champion:  I found at least one more modern Champion plug fitted with this metric 0.7mm Thread - Champion N62R (1970's-80's racing plug.  I would not be suprised to find more modern Champion plugs also fitted with this metric thread

- Lodge : This is probably the most difficult make of plug to identify thread for - as I found plugs of same 1930's - 1960's (pink ceramic) era with both metric and UNC thread type.  Those found with this 4mm x 0.7mm thread were - RL51 (the famous racing type plugs so favoured on Manx Norton's, 7R's, KTT's etc) / 2HLN / 3HLN

- 3 BA Thread (0895_3 and 0895_6):  

    -  KLG (very early?): I have read that 3 BA thread were fitted to a few spark plugs.  In my own collection I have only found one plug that uses this thread - but it is the very early KLG Brown Mica ceramic type - model number LK1 (the oldest plug in my collection).    It should be noted that a similar KLG plug to this one - the HS1 type was listed as original fitment for Douglas 2 3/4hp models (amd I would be interested in purchasing if you happen to have 2 of these in working order!)

- 4mm x 0.75mm Thread (0895_7):  

  Similar to the 3 BA thread, I have read that the 0.75mm pitch (4mm) thread was also sometimes used on spark plug HT nuts.  In my own collection I have only found one NGK plug (and an obscure one at that!) that uses this thread, but I have made a small quantity of Champion style nuts with this thread, just in case you want one!:

    -  NGK:  I have one older style NGK plug - an unusual C10M (see photo) plug which employs this less well known 0.75mm pitch thread.  It may also have been used on other early NGK or other makes of more modern plugs.  

- Other thread types not catered for:  I have one other pluge - an 18mm Lodge from the 20's-30's which has white porcelain and a larger 10 UNF fine thread.  I think  this plug is possibly from a motor car, and the top thread may be intended for a wire style HT top clip, not knurled nut.  I have not made nuts for this obscure plug - but if you know of a this or other threads (with some market!) I may consider making a small batch to htat thread (email our normal sales@racingvincent.co.uk).

Final point.  I am not intending to make any other brass spark plug parts in the near future, but if you believe there is a particular type missed or fitted to early Edwardian or Norton motorcycles - then let me know and we will consider making a batch.

Likewise - with older style spark plugs, we are able to supply a small quantity of the rare KLG 18mm long reach plug (similar to fitted to early Douglas motorcycles and possibly some early Norton engines) - but do not have any plans to supply others.  However, if anyone knows of good quality 18mm long reach plugs still available, we would be interested to hear, thanks 

- Woven cloth HT lead of the type originally used on many competition and roadgoing motorcycles from the early 1920's through to the 1940's.  Ochre/Orange in colour with black flecks - this HT lead is sheathed in a durable and waterproof covering that gives a very authentic look - as per the celluloid covering of the original period HT lead.  Price is per foot

This HT lead looks great on any period restoration pre-1950's, but particularly good on competition motorcycles - where this high quality type lead seemed to have been more commonly used (rather than the standard black rubber HT lead we also sell, used on many roadgoing models).  I have seen original competition BTH magneto's fitted with this style of HT lead - although in all cases, the original celulloid was perished and the HT lead was no longer usable.

When ordering - quantity of 1 equals 1 foot (I normally find 18" to two feet is the ideal length for a BTH KD1 on a Norton SOHC engine).

As you can see here, I have shown photos of it being used on some of my Norton BTH magneto's, but also I have used it on my veteran 1919 Douglas model, in conjunction with original brass HT knurled spark plug fittings - where it looks really excellent.  

Note Spring 2019:  I have been looking for a supplier of this type of competition HT lead for many years, so am really pleased we are now able to offer it.  Not cheap (it is manufactured  in the US), but looks excellent and I will be fitting it to some of my restorations in the future

Shouldered 3/8" Whit Hex gearbox belt pulley nut to fit Douglas 2 3/4hp 2-speed (and 3 speed?) gearbox's - in stainless steel with linished hex. 

This shouldered nut is CNC manufactured in stainless steel, with imperial 3/8" Whit hex spanner fitting and correct 7/16 x 20tpi whit form thread (not UNF).  The overall length of the nut is 0.750", but the thread is only 0.500" of that depth (this being the length of thread on the gearbox shaft) - this type of shouldered nut meaning it is easier to get a ring spanner to tighten the nut, when used in the recessed type of belt pulley often fitted to this model.

In truth, I cannot guarantee that the original Douglas nuts were of identical profile, as the early Douglas spare parts catalogs show various numbers and do not have any clear picture of what they look like - but I manufactured this nut profile to be a good fit in my own 1919 Douglas belt pulley (as per photos), and it's length allows me to finger tighten the nut easily, then get a socket or ring spanner easily to it. 

I think it also looks nice and period correct, if not using the tin cover (which was sometimes fitted over pulleys).  It is CNC manufactured in stainless steel , but we linish the faces of the hex as well, therefore it is a very pretty nut.

The thread of the nut is 7/16 x 20tpi, and this is certainly the thread fitted to the (various) 2 speed gearbox's I have - however, this nut may also fit other Douglas 2 and 3 speed gearbox's of similar era - please check the OD and thread of your own gearbox before ordering.  Likewise, I see no reason why this nut cannot also be used with the other commonly fitted belt pulley of similar era - that being the type without recess and no holes drilled (I have another gearbox/pulley of that type for a second Douglas project I have)

This 'variable' item listing offers a number of 17/64" x 25tpi fasteners, as fitted to Douglas 2 3/4hp and 4hp motorcycles in Edwardian times.  This diameter and thread size was obscure - and specific to Douglas models of the Edwardian era, and has not been commonly available for many years.

As part of restoring a 1919(ish) Douglas 2 3/4hp, I have come across a number of fasteners and fittings which were originally 17/64" diameter with a 25tpi thread.  This is an obscure size, half way between 1/4" and 5/16" (which have always been the 'normal' imperial diameter size for British motorcycle fittings of this type), and to my knowledge, is exclusive to early Douglas motorcycles.

I gather the rationale for the Douglas motorcycle company adopting these different sizes, was primarily it would mean that customers had to come back to Douglas themselves when searching for spares!  However, as these thread and diameter types have never been adopted by any other company - it is now an issue for Douglas owners if trying to restore a motorcycle where those fasteners using this thread type are old, badly corroded or just plain worn out!

I found this myself, when sympathetically restoring the original induction pipe and Amac carb on my own project.  I did not want to replate the original Amac (Douglas type) carb - but could see the original long induction pipe studs which pass either side of the carb looked very badly corroded and worn.  Replacing these with new stainless steel studs (with 17/64" x 25 tpi threads both ends) has transformed the overall look of the carb.

As can be seen in the accompanyning photographs - amongst my own collectoin of Douglas 2 3/4hp parts I have 3 induction pipes - but the two shown both came to me looking unrestored and untouched from new (and actually both with what may be WW1 paint on them, indicating they may have been of Ex WD WW1 bikes).  The one with the Amac carb fitted had longer studs fitted, and small 'reduced head' hex nuts fitted, while the second induction pipe had a much shorter stud, but with a normal size nut on it - all these looked original and had 25tpi threads on the nuts.

I have used both of these pipes/fittings as templates to directly copy the dimensions of the fastenings listed here.  All parts are CNC machined in stainless steel and look very nice.  The 'reduced head' nuts are an obscure hex size and required milling from a larger diameter bar - which look particularly pretty (but sorry not cheap, due to machining time required).  The larger nuts are also correct imperial hex, and flats linished.  

Incidentally, I am indebted to to an article posted by 

Note: apologies these items are not cheap - but to make them has entailed purchasing custom taps/dies (as well as CNC thread inserts) and being an obscure diameter, the studs are turned down along their entire length from a larger diameter stainless steel bar.  Therefore a lot of setup effort for small batch's dictate a higher price than similar commercially available fastenings

Table of 17/64" Fastenings Available (which may be added to in the future:

By the way - I am indebted to an article written by Christopher Wright on the Douglas Forum website in 2004, which list all the main Douglas 2 3/4hp fastenings, including 17/64" fastenings:

https://www.douglasmotorcycles.net/index.php?topic=1102.msg20395#msg20395

The fittings listed here may also fit some of those other uses of this thread size.  If you have an original fitting you would like to see included, you can email us on sales@racingvincent.co.uk and we may consider producing it

Good quality copper/asbestos type washer to fit both inlet and exhaust manifold nuts on Douglas 2 3/4hp models.  They should also fit exhaust on EW Models.  Price is per bag of 4.

These are copper/absestos type 'crushable' washers to fit both the inlet manifold and exhaust manifold nuts on Douglas 2 3/4hp models.  They may also fit 4hp models and the later EW model inlet manifold.  If you are nut sure, email for dimension details at sales@racingvincent.co.uk

Note:  although traditionally, this type of heat resistent washer is referred to as 'copper/absestos' type, they are actually mineral filled, absestos having been obsolete and dangerous for many years.

These should be replaced every time the inlet or exhaust nuts are untightened, to ensure proper sealing.  Price is for a bag of 4 washers.

This item listing is for Douglas 2 3/4hp Inlet or exhaust nuts, with milled slots - CNC manufactured from stainless steel, but at this stage is for enquiry only.

As I update this listing (5/10/2020), I have written the CNC programs and produced a small batch of these nuts for my own 1919 Douglas 2 3/4hp restoration project.

However, at this stage I only had enough billets left over from a previous job to make them for my own bike - and because some work is required to remove old ones off an original exhaust system (or the fixed side) of inlet manifolds - I am not sure how many Douglas 2 3/4hp owners there are that would want these nuts.  If I have enough interest, I will purchase a full stainless bar, cut into billets and make a further batch, as per the ones shown here.  

If you want more information or would like a set of these nuts, then email us at sales@racingvincent.co.uk and will consider making a full batch.

They are CNC manufactured from stainless steel billet and original nuts were used for the pattern.  As you can see from the picture - polished they look just like bright nickel plated, but will not rust and look very pretty.

I believe these were the same style as fitted to EW Cylinder heads - and I have trial fitted to a spare head I have, but only the inlet side, as the exhaust port on EW heads has a larger thread diameter