The BTH KD1 Competition magneto was the standard fitment to competition Norton Internationals and SOHC Manx Nortons. The competition versions (identified by a brass plate on its side reading either 'TT Magneto' or 'Dirt Track Magneto' and having the icompetition designate in its serial number) were fitted with platinum points and a manual advance/retard mechanism with a 3 screw inspection cover. I can supply most parts to fit this magneto and also occasionaly I have second hand parts as well. PLEASE NOTE: Some of the prices quoted in this section - particularly for small stainless steel screws may seem expensive compared to other commercially available nuts and bolts. Please bear in mind that this is because they are being made specially in small batch's for this magneto. Unfortunately the machinist charges for the number of machining operations - not the size of the screw!!

This item is the 15 tooth magneto sprocket that is driven by the chain from the oil pump gear sprocket (SOHC models) or inlet cam (OHV, SV models), and fits on the end of the magneto shaft (either Lucas Magdyno or BTH KD1). These items are just the same in profile as original sprockets - the magneto sprocket being recessed, just as the original was - and is of the type fitted to almost all Norton single cylinder models from the 1930's to the late 1950's - i.e. SOHC, OHV and SV models

Price is Each.

We manufacture these sprockets in-house, on modern CNC machinery and to a very high standard. They are then hardened (the slight black, mottled finish is as a result of the hardening process).  They are supplied sprayed in Duck Oil (the wet look in the photographs) to prevent rusting in storage.

They should fit most Norton singles from the late 1920's to the late 1950's - including SOHC models, OHV and Side Valve models.  An original 'New Old Stock' Norton magneto sprocket was used to give the correct dimensions and as part of the manufacturing process we ensured they fit on both Lucas and BTH magnetos - as can be seen from the accompanyning photographs.

Although we are not experts on other marques - we believe this same sprocket design (and offset) may well have been used by other motorcycle marques of the 1930's-50's - particularly those models fitted with Lucas Magdyno units.  If you require more information on these sprockets and offsets - you can email me at paul.norman@racingvincent.co.uk.  We have certainly sold far more of this type over the years than we have the engine side magneto sprocket - so we can only assume a number of non-Norton customers are buying them!

We manufacture these sprockets in-house, and do not offer them to any other outlet, they are exclusive to ourselves.  We used original Norton sprockets to ensure dimensions were as original, and the spocket tooth profile is the correct CNC generated profile for the imperial Renolds chain that we can also supply for most Norton single models.

Note: Fitting magneto sprockets - it is always best when fitting sprockets, to smear some fine grinding paste on the taper fit of the sprocket and gently grind the sprocket to the taper, to get a perfect fit. This is achieved when you have got a matt grey finish on both sprocket and taper. Ensure you fully remove the grinding paste before final fitting. Always use a 'puller' to remove the sprocket, do not try to lever the sprocket off with a screwdriver, as this will almost certainly damage the timing case. A tip when using puller's to remove sprockets - fit puller and screw central bolt until a good tension is reached, then give the end of the puller bolt a sharp sideways tap with a mallet - the jarring will easily loosen the sprocket

Update March 2024:  Now back in stock - we have just had a new batch of these manufactured.  See also Item 0392, the matching magneto side sprocket

This item is the 15 tooth Norton single magneto chain sprocket on the engine side - that drives the chain to the magneto sprocket, it fits on the end of the oil pump drive gear (SOHC models) or inlet cam (OHV and SV models). 

These sprockets are manufactured to to the original Norton profile, and were as used on most Norton single cylinder models (i.e. SOHC, OHV and SV singles) from the 1930's to late 1950's.   When manufacturing these sprockets, we used an original Norton 'New Old Stock' sprocket as the pattern.

Price is Each.

We manufacture these sprockets in-house, on modern CNC machinery and to a very high standard. They are then hardened (the slight black, mottled finish is as a result of the hardening process).  They are supplied sprayed in Duck Oil (the wet look in the photographs) to prevent rusting in storage.

They should fit most Norton singles from the late 1920's to the late 1950's - including SOHC models, OHV and Side Valve models.  The only difference to the original Norton design - is that we do not include a slot for a 'woodruff' key on these sprockets - as it is almost universally accepted that the use of a woodruff key on this sprocket is unnecessary - and actually can be quite harmful, as it is the taper that gives almost all of the grip, and if a woodruff key is used that sits even a fraction too proud  of the slot - it will result in a lack of contact of the taper, and therefore more chance of failure).  FYI - I have never used a woodruff key on this engine sprocket in 40 years of ownership of all varieties of SOHC,OHV and SV ownership.

We manufacture these sprockets in-house, and do not offer them to any other outlet, they are exclusive to ourselves.  We used original Norton sprockets to ensure dimensions were as original, and the spocket tooth profile is the correct CNC generated profile for the imperial Renolds chain that we can also supply for most Norton single models.

Note: Fitting magneto sprockets - it is always best when fitting sprockets, to smear some fine grinding paste on the taper fit of the sprocket and gently grind the sprocket to the taper, to get a perfect fit. This is achieved when you have got a matt grey finish on both sprocket and taper. Ensure you fully remove the grinding paste before final fitting. Always use a 'puller' to remove the sprocket, do not try to lever the sprocket off with a screwdriver, as this will almost certainly damage the timing case. A tip when using puller's to remove sprockets - fit puller and screw central bolt until a good tension is reached, then give the end of the puller bolt a sharp sideways tap with a mallet - the jarring will easily loosen the sprocket

Update March 2024:  Now back in stock - we have just had a new batch of these manufactured.  See also Item 0392, the matching magneto side sprocket

This is an excellent reproduction of the aluminium cover that was fitted to many BTH magnetos from the 1920's - late 1950's, including the KD1, MH1, KD2 and other similar models. 

It has a faithful reproduction of the correct BTH motif stamped into it as well as the correct radius to snugly fit round the KD1 type magneto body, as well as cutouts at the base of the cover, which allow for it to be fixed to the magneto by the original screws. It is an exact copy of the original, in the original thickness of aluminum.

Finish is lightly polished aluminium, but is supplied with plastic protective covering.

If your BTH magneto has knocks and scratch's on it - or is missing its BTH motif, as so many now are - then this new cover will help make it look like new again! The first photograph shows our cover fitted to an original competition KD1, with the original (and grubby) cover at the side for comparison

- Stainless steel hex head tapered screws for competition BTH housings. Drilled to take lockwire and with screwhead slot, just as the originals were - Stainless Steel.  Price is each

Not cheap as difficult to make -we CNC machine these ourselves and there are 3 seperate milling operations on them - the hex is milled to the original imperial dimension (as Whitworth hex not easily available in stainless steel), then the  lockwire holes - are in line with each hex and finally the cheesehead screwdriver slot - making it a long program to run for such a small screw, with small tool breakages not uncommon.   However, they do look the business, particularly when fitted with the lockwire! Also, being stainless steel they look very pretty and will not rust. 

Note: normally 3 of these are required per magneto (if used on a BTH KD1).  I believe they may also fit other non competition BTH magneto's - but have not tried.  Email us on sales@racingvincent.co.uk if you want more detail

This listing is for an unmachined cast aluminium 3-screw type points cover, to fit the manual advance/retard housing BTH KD1 TT model magneto.  The casting is a nice quality (lost wax) casting, with (lathe) machining boss attached, and we supply it with an engineering drawing giving machining dimensions taken from an original cover.

As you can see in the accompanyning photographs - this nice quality alloy casting replicates the outer contours of an original BTH KD1 TT magneto cover almost identically - including the unusual little vertical boss coming out from the centre, which was originally intended to allow fitment of an ignition cutout switch if required.  This could still be machined and fitted if required - but is also the main reason why a casting like this is really required to make an accurate reproduction, otherwise it could be machined from billet.

You will also see that the casting includes a machining boss - that allows the outer circumference and rear face of the castingn to be relatively easily machined in the home workshop using a small lathe (and pillar drill or similar for the 3 fixing screw holes).

And finally, to assist - you will see that this listing includes a detailed technical drawing of all the machining dimensions, them being taken from the original BTH KD1 cover shown in the photographs.  However - it is the customers responsibility before machining to ensure that the magneto that this cover will be fitted to corresponds with the dimensions on the drawing - this magneto was made for many years, and like all old motorcycle manufacturers - there can be slight variations in dimensions and tolerances over the years.  It is worth noting that the protruding ring on the inside of the original cover is intended both to locate the cover on the original advance/retard housing - but also to help stop the points ring sliding out, so you should check that the protuberence is only enough to to stop the ring coming out - but should not be touching the points ring once gasket fitted, so as not to make that difficult to move.

It is also worth noting that original covers had a condensation filter fitted.  As can be seen from closeup photos of the original BTH inner cover, this was simply a brass or steel disc, with 4 small holes drilled that were positioned at the top of the cover, so to allow air into the points area, but to capture condensation or damp.  On the original cover, the recess this disc was fitted into was recessed around the surrounding area, but I believe this was because BTH manufacturing then allowed a tool to crimp around that disc.  In our drawing the recess is not included - as if fitting the disc now, we would retain the disc with industrial Loctite retainer, then just centre punch the alloy around the circumference of the disc.

Finally, you will see the original cover has a hole cast in the small boss area on the inside of the cover.  This was to allow that hole to be fully drilled by original customers and fit a cutout mechanism.  We have not included that on the drawing, but there is no reason that could not be fitted.  It would originally have been for a 2BA or similar screw that is retaining a strip of spring steel approx 1.5" long which is bent so when the cover is fitted to magneto the spring steel touches the centre points plate retaining screw on the magneto.  Then where the 2 BA screw protrudes through the cover, a nut would be used to retain the spring, but additional thread - so that a wire with connector could be fitted - running to a cutout switch on the handlebar.  The most important thing about fitting this mechanism (if required), was that the 2BA screw and spring must be entirely insulated from the cover itself, otherwise it will just permanently earth the magneto.  Normally therefore, that hole was drilled larger than the screw so a fibre or non-conducting material could be fitted to isolate the screw.  Email if you wish to fit a cutout mechanism and require more details - some mags used them, others did not.

Final Note - Jan 2021: Depending on popularity - we may be offering this cover fully CNC machined in the future and with condensation disc fitted.  Obviously the machined price will be considerably more than shown here, but email on sales@racingvincent.co.uk if interested

Hex head bolt with screwdriver slot to fit the 3-point competition BTH KD1 cover.  Worth having a couple spare as they tend to get lost easy .  . . I have lost them frequently at race meetings! 

Each screw supplied with small flat steel washer

(note: sometimes I get these as plated steel, other times as stainless steel - both are nice quality)

These are the small round headed screws that retain the alloy BTH embossed cover fitted to most BTH magnetos, as shown here. 

These screws are CNC turned in stainless steel by us, using an original BTH round head screw as a pattern and come with washers. 

Price is for a pair of screws, with two stainless washers included 

- Competition Cover (3 screw type) paper gasket for BTH KD1 competition magnetos

Correct size shims to fit BTH KD1 magnetos and other BTH magnetos with similar housing - i.e. KD2, KH1, KH2 etc.  See detail listing for more information.  

These are the square shims to fit BTH KD1 magnetos, and other magneto's with similar bearing housnigs.  They are used to shim the magneto armature by fitting between the main body and the rear bearing/cam ring housing.  As you can see from the main photo - they are a perfect fit over a BTH rear housing flange.#

The lip of the BTH housing in the photograph that this shim fits over is: 2.165" (and our shims are @2.175" ID to fit over this)

We sell this shim in two thickness's - 0.008" (8 thou) imperial, or 0.004" (4 thou) imperial, so as with any shimming of magneto's if you require a greater gap you will need to fit multiple shims.  Also - original BTH magneto shims I have seen were sometimes in steel and sometimes in copper.  These are in proper shim steel - and the difference is nominal, as both are conductive. Please state which thickness shim you require when completing your online order in the Comments section

28/2/20:   I am pleased to be able to offer these again - as they have been unobtainable to us for about 5 years.

Final Note:  The inner diameter of the large circular cutout on these shims is @2.175" - which is correct for BTH magnetos.  Lucas magneto bearing housings are of a fractionally larger diameter lip and take a slighlty larger shim than the BTH shim.  I did attempt to very carefully linish out one of these 8 thou BTH shims with a flapwheel in a handdrill, while holding the shim vertical in a vice with soft jaws and holding the shim with my fingers at the top - as you can see from the last photograph - I was able to linish it enough to fit a Lucas NR1 racing magneto housing.  Although i cannot tell you it was particularly easy - it took about 10 mins for an thou shim (and please follow all normal health and safety rules!) - but it did open up as you can see in the last photograph.  For the 4 thou shim, I doubt you will be able to linish, but might be possible to trim with sharp scissors. So if you find Lucas shims are not available, this may be an option. However - as you might expect . . . if you wish to try one for this purpose - I will not take Returns if it does not work well! (note - I may get a batch of Lucas shims made in the future but no plans at the moment - i.e Feb 20).