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Norton Engine and Gearbox Sump Plugs: All Types - Pre and Post War and Racing Type (Each)

Product no.: 1101 SumpPlugs

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This is a 'Variable' Listing, showing various types of Norton sump plugs - as were fitted to most Norton models from the 1920's through to the 1950's, both engine and gearbox, and also some additional 'Racing' type, either drilled for Lockwire and even a couple 'Wasted' for weight saving.  All are modelled on original Norton sump plugs - with all major dimensions replicated.  Price is Each

Types Available are as Follows:

Note: I have desctribed below the different variations, and wherever possible - the most common fitment of each . . . to the best of my knowledge from having stripped various original engine and gearbox's over the last 40 years, as well as talking to friends and customers where necessary.  However, providing thread and fitment is correct - you may find these plugs styles also fitted to other models, or different to below:

Update 11/7/22:  At the time of listing this batch - all 1/4" BSP brass sump plugs (as fitted to most gearbox's and all pre-48 engines for all models) are offered in brass - which was an original Norton finish.  However, I will be looking to get some of these plugs Satin Nickel Plated in the next 3 months - state when ordering if you wish to reserve a nickel plated version.

ID Type Thread Attributes Normal Fitment?
1101_1 - Shallow Curved 1/4" BSP

- Norton Shallow/Curved Type

- Brass (unplated)

- Supplied with 1/4" BSP Dowty seal

- Normally seen fitted to Norton road model Gearboxs , both Pre-war and Postwar

- I have also seen this type fitted to OHV and SV engines, late 1930s to mid 1950's

- This type has a shallow hex head with a distinctive 'Norton' type curve to the head

- Ours are identical to the original item, including depth of groove for washer, and slight undercut to avoid hex digging in to casting.  In one of the photos can be a seen a genuine 'New Old Stock' Norton item (plated item on the right in photo), used as the pattern for ours 

1101_2

-Shallow Curved

- Lockwire

1/4" BSP

- Norton Shallow/Curved Type

- Brass (unplated)

- Drilled through head to take lockwire

- Supplied with 1/4" BSP Dowty seal

- As above

- This type is drilled for lockwire - normally found on competition type gearbox's and engines

- Essential fitment if taking your bike onto a track event

1101_3

Shawllow Curved

- Slotted

1/4" BSP

- Norton Shallow/Curved Type

- Brass (unplated)

- Slotted for Screwdriver

- Supplied with 1/4" BSP Dowty seal

As 1101_1 but slotted for a screwdriver

- I have seen these fitted to both gearbox's and pre-48 eingines

- Seem most common on late 1930's - 1948 engines for road going models - SOHC/OHV/SV, as the slot was more accessable for a screwdriver on sump of crankcase, when plug at side of sump

1101_4

Shallow Curved

- -Slotted

- Lockwire

1/4" BSP

- Norton Shallow/Curved Type

- Brass (unplated)

- Slotted for Screwdriver

- Drilled for Lockwire

- Supplied with 1/4" BSP Dowty seal

As 1101_3 above, but these are also drilled for lockwire

- Normally fitted to competition bitkes, but very useful for ensuring it does not come loose and lose oil on road bikes

- Essential fitment if taking your bike onto a track event

1101_5

- Shallow Curved

- Lockwire

- Reduced Weight

1/4" BSP

- Norton Shallow/Curved Type

- Brass (unplated)

- Drilled for Lockwire

- Centre bored and head shaped to reduce weight 

- Supplied with 1/4" BSP Dowty seal

- This sump plug starts off as the Shallow Curved type - as seen on most gearboxs and pre-48 engines, however for these - as well as drilling them for lockwire, we also bore the centre, and shape the head profile to reduce weight

- Although rarely seen on production bikes out of the factory, it was a normal thing for the serious 'Tuners' to do on a competition bike - as they are noticeably lighter than standard

- I will also be the first to admit - they look very pretty and are a 'focal point' on any competition bike - for that extra bit of Bullshit!

1101_6

Norton Deep Head Type

- Slotted

1/4" BSP

- Norton Deeper head /shallower Curve (Pre-War) Engine Type

- Brass (unplated)

- Slotted for Screwdriver

- Supplied with 1/4" BSP Dowty seal

This sump plug is similar to the 'shallow curve' type above, but has a slightly deeper Hex, and the 'Norton' type curve is less pronounced than the type above

- Although not definitive - I have normally found this 'deeper head' type fitted to Pre-War models of all types = i.e. SOHC, OHV and SV models

- I cannot be sure when this type of sump plug was first fitted - but I know that customrs with engines as early as 1930 have provided me examples of this type fitted to their engines 

- May have been fitted to 1920's models - but have not had this confirmed yet (please email me if you a 20's model - and can update listing, thx!)

1101_7

Norton Deep Head Type

- Slotted

-Lockwire

1/4" BSP

- Norton Deeper head /shallower Curve (Pre-War) Engine Type

- Brass (unplated)

- Slotted for Screwdriver

- Drilled for Lockwire

- Supplied with 1/4" BSP Dowty seal

This plug is the same as 1101_6 above, but this version, as well as being slotted, is also drilled for lockwire

- This type would normally be found on the engines of Pre-1948 SOHC models - particularly competition models

- Essential fitment if taking your bike onto a track event

- Note: on many Norton SOHC engines (particularly pre-War), there were two sump plugs fitted - one on the Timing side crankcase, at the side of the sump, and another in the 6pm position of the Drive side crankcase.  This plug type will fit both sides - but we also offer an 'improved' lipped type (below), for the Drive Side, which gives better seating for a fibre washer

1101_8

Norton Deep Head Type

-Lockwire

- Reduced Weight

1/4" BSP

- Norton Deeper head /shallower Curve (Pre-War) Engine Type

- Brass (unplated)

- Drilled for Lockwire

- Centre bored and head shaped to reduce weight 

- Supplied with 1/4" BSP Dowty seal

- This sump plug starts off as the Deeper/Shallower Curved type - as seen on Pre-War engines, however for these - as well as drilling them for lockwire, we also bore the centre, and shape the head profile to reduce weight

- Although rarely seen on production bikes out of the factory, it was a normal thing for the serious 'Tuners' to do on a competition bike - as they are noticeably lighter than standard

- I will also be the first to admit - they look very pretty and are a 'focal point' on any competition bike - for that extra bit of Bullshit!

1101_9

Norton Curve Head

-Improved 'Lipped' Design

1/4" BSP

- Curved Type Norton Head

- CNC machined from Brass bar

- Improved 'Lipped' design, with milled Hex - improved seating of washer

- Slotted for screwdriver and drilled for lockwire

- Supplied with 2 x 1/4" BSP Copper washers

We have manufactured this sump plug to our own 'improved' design - in that these are CNC machined from 0.750" round Brass bar, and then the Norton Hex head is milled as a seperate operation. 

- This broader lip provides a much better seat, when using red fibre washers, to give better sealing

- We manufactured this lipped sump plug specifically for the drive side of SOHC engines that have the 6pm drain plug, with a wide milled face - ideal for this lipped nut (see photograph)

- I have also seen a similar lipped brass sump plug fitted to an original Pre-War Manx upright gearbox - but cannot guarantee it came from the factory with that plug fitted - although it looked nicely tarnished!

- Supplied with copper washers - but red fibre can also be used as lip gives ideal seal

- More expensive than other plugs - as additional milling required and more expensive material used

1101_10

Norton Curve Head

-Improved 'Lipped' Design

- Reduced Weight Racing Type

1/4" BSP

- Curved Type Norton Head

- CNC machined from Brass bar

- Improved 'Lipped' design, with milled Hex - improved seating of washer

- Supplied with 2 x 1/4" BSP Copper washers

As above, this is our own improved 'Lipped' design sump plug - providing a wider face for improved sealing with red fibre washers

- This version also has our centre bored 'reduced weight' head design - so looks particularly pretty, as well as being lighter than the version above

- it is also drilled for lockwire, ideal for racing engines - particularly the drive side SOHC 6pm position hole, or racing gearbox's

- Supplied with copper washers - but red fibre can also be used as lip gives ideal seal

- The most expensive of our sump plugs, as a lot of machining time to manufacture

1101_11

Post 48 Type Sump Plug

- All Models, original design

-Stainless Steel

1/8" BSP

As fitted to most Norton models 1948 onwards

- Fitted to 1948 onwards engines, where sump plug is at bottom of crankcases sump 

- This type copies original design exactly, other than CNC manufactured in stainless steel

- Supplied with 1/8" BSP Dowty seal

It seems that Norton changed the design of the engine sump plug in 1948 - that being to a smaller diameter 1/8" BSP thread, which had a much finer thread than the previous 1/4" BSP plug.  I am told by other knowledgable Norton people this continued to 1961.

- I presume the reason for moving to this finer thread was because the position of sump plugs was also moved to the base (i.e. underneath) the sump of most engines - where there was not much metal in that casting.  (most OHV engines 48 onwards have a ramp under the sump of the engine surrounding the sump plug - to avoid the sump plug being pulled out, if 'grounding' the bike)

This plug copies the original Norton design sump plug exactly, including lips, other than being CNC manufactured in stainless steel.

Please ensure your engine still has the 1/8" BSP thread fitted before purchase (see also 1101_13 below)

1101_12

Post 1948 Sump Plug Design

- This type deeper head and drilled for Lockwire

1/8" BSP

This is the Post 1948 type 1/8" BSP sump plug

- This type has a slightly deeper head than standard, to allow it to be drilled for Lockwire

- Stainless Steel

- Supplied with 1/8" BSP Dowty seal

This Sump plug is similar to 1101_11 above, however we have deepened the head slightly to allow it to be drilled for Lockwire

- As would have been fitted to Post 1948 SOHC models for competition use (but also useful for any Post 48 models, and required if using your bike at any track event

-We have been careful to ensure the depth of the head on this type still does not protrude further than the cast ramp on the crankcase (on OHV crankcases tested - see photo)

1101_13

Post 1948 Sump Plug Design

- Larger diameter thread

7/16" BSF 

- Same dimensions as 1101_11, other than thread - which is a larger diameter 7/16" (0.436") x 18tpi BSF thread

- Stainless Steel

- Supplied with Copper sealing washer

- I am told that engine sump plugs were standardised with 1/8" BSP thread on all models from 1948.

- From 1948, the location of sump plugs (on all models I believe) was moved to the base of the crankcase sump, and a small ramp cast into crankcase, to ensure the sump plug would not be ripped out, if grounding the engine

- However, this thread/diameter does seem to have had a reputation for more easily stripping than the earlier 1/4" BSP plugs, previously fitted. 

- I have two original mid 1950's OHV/SV Norton crankcases in my possession, which I am confident have not been touched since the 1960's.  On careful examination - both sump plug threads fitted to these crankcases are tapped to take 7/16" x 18tpi BSF sump plugs.  Although both threads look original and good condition (see photo for this listing) - which means it may be an original, if unusual, thread . . . it is more likely this was a common 'replacement' thread, fitted in the 1950's/60's, if original thread stripped

Therefore - I have made a small batch of brass sump plugs - which are a hybrid of the original design, but with larger 7/16" x 18 BSF thread fitted. 

Also a suitable replacement - if your original 1/8" BSP thread has stripped . . . but satisfy yourself this thread is correct for your needs and you are able to tap crankcase to this size

1101_14 1/4" BSP Dowty Seal (Each) 1/4" BSP Modern type nitrile inner seal 'Dowty' Washer

- As supplied with each 1/4" BSP sump plug - these are a more modern sealing design and easier to fit than red fibre washers

- This is for a single Dowty washer, which ideally should be replaced when plug removed

- Note we also sell correct type Red Fibre washers if you prefer - Item 0092, but remember, they nee to be a tight fit when fitting onto the thread, to ensure they do not wobble at the final groove position

1101_15 1/8" BSP Dowty Seal (Each) 1/8" BSP Modern type nitrile inner seal 'Dowty' Washer

As above, but this is the smaller BSP size to fit the 1948 - 61 original type sump plug

We also sell copper alternatives - see below

1101_16 1/4" BSP Copper Sealing Washers (Pair) 1/4" BSP

- Soft copper sealing washers

- 1/4" BSP

- Sold as a pair

If you prefer a more traditional seal (other than red fibre) - we also offer these copper sealing washers, as a pair

- they are 0.75mm thick, slightly thinner than most fibre washers - so can be fitted singularly, or as I prefer - as a pair, to give more 'sponge'

1101_17 1/8"BSP Copper Sealing Washers (Pair) 1/8" BSP

- Soft copper sealing washers

- 1/8" BSP

- Sold as a pair

- As above, but for hte 1948/61 original type plugs, an alternative to Dowty or red fibre washers

- Sold as a pair

 

Background and Fitting Notes:

These are CNC manufactured by ourselves, but using original Norton sump plugs as a pattern - which we have copied exactly - including chamfers, grooves (most of these sump plugs have a specific type of groove behind the thread, which I assume was to let the red fibre washer to 'mush out' slightly and give more effective sealing) - and of course, the correct Norton head profiles.  We also linish (with fibre linishers) the head after manufacture to remove burrs, and then finally, every nut is ran down a thread gauge, to ensure the thread is deburred.  We have also manufactured additional varieties with cross-drilled holes for lockwiring - for track and competition use, and also some 'lightened' types with a very pretty drilled head.

Norton sump plugs for Norton singles were manufactured in their 1000's over a 50 year period - and as always there were slight variations and tolerances by batch - but we have compared multiple sump plugs and have tried to adopt 'std' tolerances wherever possible.  However, when fitting, try and ensure the thread fitting you have selected is correct for your model - always grease the thread first, and if not sure - play safe and confirm thread in casing first.

Note - Each of the sump plugs (between 1101_1 and 1101_12) comes supplied with a BSP Dowty sealing washer.  These are much easier to fit than the traditional Red Fibre Washer (which must be a very tight fit onto Norton sump plugs - and are difficult to fit - if they go on easy, they will 'wobble' when they get to the grooved area that all these sump plugs have). 

Dowty sealing washers are a more modern design - consisting of a steel outer with sealing nitrile inner - and are used in most modern fittings for sealing plugs.

We also sell these 1/4" or 1/8" BSP washers seperately (1101_14 and 1101_15 respectively), as ideally they should be replaced every time an oil change is performed.

We can also supply the traditional Red Fibre washers (Item 0091) if youj wish to use the traditional style washer - particularly on the Lipped type washers - but note these are normally a bit more difficult to fit.

Final point - if you have a different type of sump plug to the type shown here, and think it is original (i.e. early 1920's etc) - then feel free to email us and we may consider manufacturing a batch

 

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