Correct (and as per original) 1/4" BSP 'One Way Valve' - as fitted to all Norton singles, including all SOHC, OHV and SV models - this item screwing into the recess just above the drive side main bearings, allowing the engine to breathe correctly

This special 'one way' valve' looks almost identical to the 1/4" BSP 'straight through' breather that was also fitted to various Norton single cylinder engines, but serves a very different purpose - it being fitted just above the driveside main bearings, and allowing the engine to 'breathe out' but not ''breathe in', which is achieved by the use of small bearing fitted inside the valve.  

This valve was fitted to all SOHC (and DOHC) crankcases (as well as all OHV and Side Valve models) behind the drive side mainshaft casting. On original engines this special valve is almost always badly chewed engines and is now almost impossible to find. They were also fitted originally in bare brass, as shown. This version, like most items I am reproducing, has been manufactured to be indistinguishable to the original, and as normal in this case an original was used as the pattern.

The outer breather union is machined to the same Whitworth spanner hex as the original, is plain brass and has the same thru-hole size as original. It is threaded internally to take a small screw in insert, which retains a small ball bearing (in stainless steel, to prevent corrosion), which provides the one-way breather mechanism.

These should be fitted with the inner screw in section showing uppermost (just in case you are not sure), to ensure the breather allows pressure to escape out - not the other way round.  I get asked by lots of single cylinder Norton customers why their engine may be leaking more oil than normal or not oiling properly - I always direct them first to check if this one way valve has been replaced by a 'straight thru' breather by mistake, or even worse - it is fitted, but is screwed in the wrong way round!

As a final point - like the original Norton Items, our breathers can be stripped for cleaning if ever needed - but it is important to note which way the inner portion is screwed in, as although they look almost identical both ends - they are actually 'sided' with one slightly different to the other.  Once re-assembled, you should always blow through them, to ensure they will only passage of air in one direction

Update July 2023:  Now back in stock - of this popular (and for most Norton singles - very important) part.  FYI - these valves have a lot of setup time and multiple ops - to provide correct dimensions on all parts, including milling.  However - despite the cost of 'Imperial' hex brass bar having almost tripled since we last manufactured a batch 2.5 years - our price increase over that time has stayed far less.  

Good quality Copper washer suitable for 1/4" BSP fittings on most Norton SOHC/OHV/SV engines - i.e. One Way Valves, Breather Unions and Crankcase Oil unions. They can also be fitted to 1/4 BSP petrol taps if required.

Sold as a pack of 3

Update 2022: These copper washers are far better quality than most others I have seen available - they are a good 'close' fit onto a 1/4" BSP thread (most are not), they are not too wide on their outer diameter - just right for Norton unions, and most importantly are a genuine 1.4mm thick - which is perfect for our unions and thicker than most other similar copper washers available.

These may be slightly more expensive than some others you will see - but are the best available I can find (and I have been to a lot of suppliers over the years!)

Note: for many application of breathers and unions on Norton engines - it is usual to find both copper and red fibre washers fitted (sometimes even both togeher!).  I think it is personal preference and have used both types myself - but tend to favour these copper washers over red fibre on breathers and one way valves.  However, if you want a washer that will 'Screw' onto the thread of a Norton 1/4" union or sump plug . . . but is then a good fit on the shoulder behind the thread (which some Norton unions have) - we also sell a special Red Fibre Washer, which we specially thread for this purpose - see item 0249

These are the unions that screw into the crankcase behind the timing chamber - it is the smaller 1/4" BSP side that screws into the crankcase, the larger side is 3/8" BSP and takes the distinctive large oil pipes fitted to Norton Internationals.

These are CNC machined in-house by ourselves from good quality imperial Hex brass, to the original Norton dimensions.

As with the smaller breather union, we also offer a cheaper modern alternative using modern AF spanner sizes on the hex, but the hex on those are larger - while the version you see listed here are copied from a pre-war orignal and are made with the correct Whitworth Hex spanner size and indistinguishable from the original.

I have to say that I have seen SOHC crankcases with original unions both in plain brass (like these) and cadmium plated, but I know the pattern we used for this type came from an original SOHC engine and was in plain brass, and did not have chamfers on either end of the hex (unlike modern equivelants which has a much larger AF hex, does have chamfers, and has a more modern looking cadmium plate finish) - so these brass versions shown here I think look much more correct.   Sorry they are not cheap compared to modern AF equivelant - but they are CNC machined by us - not a mass produced modern version.

Fitted to all SOHC Engines (and I believe also fitted to DOHC engines as well), with two fitted per engine (price is each).  We also sell the correct high quality wide red fibre washers to fit these and ensure they do not mark the crankcases (Item - 0112)

Part 2 of the Gasket and Seal Section lists:

Norton OHV single cylinder engine gaskets 

Email us if you have a particular gasket or seal requirement and do not see it listed here: sales@racingvincent.co.uk

Traditional brown oil resistent paper type gasket to fit on the base of 500cc OHV barrels. Also can be used for some SOHC Models. 

As you can see from the profile in the photograph, these brown paper gaskets are made with the correct profile for early - late 1950's type OHV barrels.  However it is also possible to fit them to SOHC barrels, but they may just require a small amount of 'tweaking' with sharp scissors (depending what type of SOHC barrel you are intending to fit them too).

As there were various OHV and SOHC barrels - it is also important to check any oil drain/feed holes on the barrel match up with the gasket (but again these can be quickly modified or cut with a punch or sharp pair of scissors).

Note that we also sell another cylinder base gasket - 0917, which is a different, slightly thicker oil resistent material, as an alternative to this one - but both are professionally made gaskets by the same manufaturer.

These gaskets are manufactured for us by a specialist UK gasket manufacturer

Final point 2020:  I am also considering having another cylinder base gasket made, with the slightly different SOHC profile (i.e. single vertical tube in centre and open stud corners which original SOHC postwar gaskets had - but in the meantime this gasket and 0917 are alternatives)

This is the small red fibre gasket that was fitted on to the lipped steel union on the outside of the gear oil pump fitted to all Side Valve and Overhead Norton models - and connected the oil feed to the outer timing cover. 

Fitting Notes: This gear type oil pump was fitted to all Norton OHV and Side Valve models through the mid 1920's to 1950's.  As can be seen from the photograph of an original oil pump (this one coming from a 1940's OHV engine), there was a small shouldered steel connector that pressed into the outermost face of the oil pump, which mated with a corresponding recess in the outer timing cover.

A red fibre waseher was used to give a seal between the two.  

We supply two thicker washers (which are the normal fitment size) - but also a 3rd thinner washer, in case the tolerances on your pump and outer timing cover require an additional washer to ensure a good seal.

Fitting Notes:  As this design was fitted for many years, I have seen minor variations in the machining tolerances of the steel shouldered connector that the red fibre washer presses over.  Therefore it is always a good idea to ensure that the fibre washer fitted will actually touch the timing cover mating face (it should just touch as the screws are tightened), to ensure best feed of oil.  There are various ways to do this - one of the ways I use to use was to mark the outermost face of the washer with 'Engineers Blue' marker paste, then ensure that marker touched the timing cover recess as screws were tightened - which would result in the Engineers Blue just touching the washer.  Obviously, whatever method is used - it is very important to ensure nothing enters the oil passageway.

These red fibre washers are the correct imperial dimensions (often - modern washers are too wide to fit in the recessed area in the outer timing cover - you should always check it does fit inside).  We supply two of the thicker washers - which are the normal size + an additional thin washer, in case it is required to ensure a good fit to th timing cover.  

Price is for 3 washers, 2 x thick and 1 x thin

This item is the distinctively shaped twin hole top pushrod rubber seal that was fitted to all OHV 1938-47 models.  This OHV model is easily identified because it had a seperate front rockerbox cover, which had a special cutout area to take this rubber seal - and which both pushrod tubes fed through. the later and more common 1948-56 OHV engine design dispensed with the this method of sealing the top pushrod tubes - so the original rubber seals are now extremely difficult to find - and normally original seals are ripped, soggy and ineffective.

If you look at the accompanyning photographs, you will see how these seals are fitted.

This engine, although less frequently seen than the later 1948 onwards OHV design, is close to my heart - as I owned and raced a number of bikes fitted with this engine type in the early 1980's - and I spent a lot of time scouring through old box's of gaskets at autojumbles trying to find this particular rubber seal!  Therefore, I am very pleased to now be able to offer this seal - manufactured from a high quality oil resistent nitrile rubber.  

To make it - we had our rubber manufacturer make moulds from what is possibly the only original Norton 'New Old Stock' example of this seal still surviving - it coming from an original engine gasket set I have held back from my collecting days in the 1980's.

This seal may be slightly more expensive than other similar seals for other makes and models - but that reflects that we have had to have moulds made and this seal is only manufactured in smaller quantities.  Price is Each.

Update Dec 2021:As a final point on this 1938-47 OHV engine type - we may be manufacturing a batch of the distinctive pushrods (with pushrod adjusters), and possibly the timing case cam followers - both of which have a habit of wearing out and snapping (in the case of the followers) in the near future, email us at sales@racingvincent.co.uk if you wish to go on our Wanted list for these.   And in case you have looked at the photos - and are wondering why the cylinder head in the photo looks silver - the 1938-47 OHV models were only ever listed with cast iron cylinder head, this is actually a Works alloy cylinder head I acquired 40 years ago, which I believe was made for an ISDT engine . . . one day I should rebuild that engine! 

This gasket set consists of the 2 x bottom extra thick Red Fibre seals that were fitted to the 1939-47 type OHV engine bottom pushrods.  This is particularly difficult seal to find now and we have had it made specially for us.  Price is per pair.

Background:  As can be seen from the photograpsh of an original engine - this type of OHV Norton engine - manufactured from 1938 to 1947 used pushrod tubes retained by a large hex nut, and a deep type red fibre seal.  We have had this seal manufactured specially for us by our main UK gasket manufacturer, using an original seal that came from the engine in the photograph.

This listing is for a pair of these bottom pushrods red fibre seals. 

Note Feb 2021: this particular type of engine also used a distinctive two hole rubber seal that located into a rockerbox recess for the top pushrod sealing.  We are currently talking to our rubber manufacturer to have patterns made for this seal - email us on sales@racingvincent.co.uk for an update

Final point -  the earlier type OHV engine, manufactured through the early 1930's to 1937 also had similar nuts and pushrods to this type engine, and I believe used a similar bottom gasket, although the reference number was different.  If you have a pre-37 engine, we would be glad to hear from you so we can confirm our gaskets will fit your engine - these would be supplied free of charge!

This is the oil delivery or return union that was fitted to the crankcases of pre-war OHV and Sidevalve models, then continued on the post-war OHV and Sidevalve (SV) models until approximately 1950-51 when the twin unions were replaced with a single 'cast' union junction box. These unions are CNC manufactured by us and faithfully replicate the original unions, including the correct Imperial hex spanner size.

An original brass A2/721 union (taken from a 1938-47 set of OHV crankcases, and definitely an original item from that engine) was used as the pattern to make these, and the dimensions were copied faithfully - including chamfers and differences in both ends.

Similar to the A11/721 union on SOHC crankcases and cambox's (Item 0248B), these unions have a chamfer to the hex on one end only, and that chamfer coincides with a flat end (as shown in the last photograph) - this is the end that screws into the crankcase.  The other end has a taper (rather than a flat end), and this is attach the standard 1/4" BSP tapered pipe unions.

Two are required per engine (Feed and Return).  Note: please check your crankcases if unsure, but from 1950 onwards, the OHV/SV engine crankcases were modified to use a single oil union block, instead of these seperate unions - see the photographs attached, and email us if unsure.

This is the gasket fitted to tappet covers on all OHV models (i.e. Model 18, ES2, Model 19) between 1938 - 1947.  Manufactured in cork gasket material.

In pre-war catalogs it was shown as Part Number 8899 and postwar I believe it was called A3/95 (although post war Spare Parts Catalogs showing this type of engine were rare, as it was replaced with the later OHV design in 1948. 

Although the tin plate 'Norton' inscribed tappet cover looks the same on both models - the gasket for this earlier engine is subtly different - it is an oval only, with the inner cork segment surrounding the cheesehead screw holes.  This difference is important, as if the later gasket was used - once worn, the inner parts could break off and enter the rockerbox.

This gasket is manufactured for us in good quality oil resistent cork gasket material by a well established UK gasket manufacturer - but please note, as it would be uneconomical to have just this (quite uncommon) gasket made on its own - we take the other gasket and then carefully trim away the excess to turn it into the earlier version in-house.

These are one of the most common leakage areas on this type of engine (probably because of the engine breathing or the pressed steel cover).  Although a new cork gasket like this mostly alleviates the leakage .. . when I was riding one of these models on the road regularly, I also use to smear a light layer of silicone gasket liquid over the cork gasket as well - which seem to make them more oiltight.  It was also common to find the pressed steel cover had its screw holes indented through overtightening the screws.  Turning the cover over on a flat hard surface and carefully punching the holes back flat with an alloy drift would greatly help the issue.