Information Section: Norton SOHC Engine Bearings and Imperial Bearings in general

If you are new to Norton motorcycle restoration - or indeed any classic bike restoration, then you may be more used to going to a bearing supplier for Metric bearings and finding they are available quite cheaply.  You then look here and see these bearings are far more expensive!

Well, the reason for that is that most bearings fitted to Norton SOHC engines are now obsolete or made in very small numbers, therefore if they are available they are far more expensive than metric equivelants - or, as is often the case, they are being held by specialist bearings wholesalers, who buy up any remaining stock - then hold the trade bearing suppliers to ransom!

A couple of the bearings listed in this section are a very good examples of this (see vertical bearing 0005 as the best example), however, unfortunately we are all in the same boat - without major engine surgery it is not possible to fit a modern metric alternative.  Added to this, many of the bearings fitted to these SOHC engines were variants of the standard bearing, with different tolerances as fitted to sports/racing engines, making them rarer again!

Wherever possible, I look to supply the original specification bearing, supplied by a top quality bearing supplier - i.e. RHP, SKF, Hoffman or similar.  Only if absolutely unobtainable now will I list a cheaper quality modern alternative - and I will make this absolutely clear in the listing.  I spend a considerable amount of time every time I need new batch's of bearings going to those bearing suppliers I know and trust . . . and although the bearings are not cheap, I am normally able to negotiate a slightly better price because of the long term relationship I have with them.

In many cases, original Norton single cylinder engines were fitted with 'looser tolerance' C3 fit bearings - which meant that when the alloy crankcases/cambox shells were heated up to accept the bearings - then cooled down, creating an interference fit - the inner bearing race would still run free with the minimum 'running in'.  These C3 (or 3 spot - as in earlier times they often had 3 dots stamped on the outer race of the bearing) are now the most difficult to find and are almost all obsolete from the best UK manufacturer - RHP.  We still make every effort to obtain C3 if we can, but if not we offer 'STD' fit bearings. 

It is each owners choice if they wish to fit these STD bearings, rather than original C3 fit  (many owners are not aware of C3 and may find their bike already has STD fit bearings in) - but most people (myself included) would rather fit the best quality bearing they can obtain - and just take a bit more care running the engine in to allow for this.

Bearing Packaging: Unless otherwise stated these bearings will always be 'brand new' quality supplied in original packaging with absolutely no corrosion.  However, because many of them have been on the wholesalers shelfs for a long time - Sometimes (dependent on which wholesaler the bearing supplier has got the latest batch from) the original cardboard packaging may be tatty, marked or even replaced with new boxes - all of which is absolutely normal when buying from trade bearing suppliers, but the bearings themselves will always be new - never used or corroded!   Also, you will always be able to check the outer track of the bearing itself and be able to check the maker - if it is RHP or SKF, FAG etc . . . then they will have this engraved on the outer track.

You may be able to find cheaper bearings on the Internet . . . but always check with the seller first to find out if they are original UK/European/Japanese manufacturer, or (as getting increasingly more common) a much cheaper Chinese copy.  I am not decrying this - I think eventually we may all be forced down this route - but for the moment I would suggest that if you have the choice and it is just the cost that is swaying your decision - then try and buy the best you can afford - even if you have to give up cigarettes, wine or other vice's for a few weeks! 

With all the above background said, I can only suggest you consider the mindset that I apply - given the (limited) mileage most of us do with these engines - if you buy good quality once, hopefully you will not have to buy again for a long time!

Please Note: When purchasing bearings - do not remove bearing from sealed inner cellophane packaging (if fitted) until you have confirmed it is the correct bearing for your fitment.  Sorry - but we cannot accept returns on bearings once they have been removed from the sealed plastic bag

This is the very important twin row, self centering bearing that was originally fitted in both top and bottom bevel housings in all International and early Manx engines (SOHC and earlier DOHC engines).

They are self centering, because they allow for the vertical shaft to be moved off centre slightly, and therefore it facilitates the cambox being 'swivelled' out from under the top frame tube, when working on the engine.  It also allows for any small discrepancy in the cambox being out of line with the bottom bearing housing.  They were originally made by top UK bearing manufacturer RHP (previously known as Hoffman - in case you are removing an old bearing from an original bevel housing and find one of these bearings stamped 'Hoffman').

Update January 2024:  As I am sure most owners of SOHC Norton engines know - these bearings have been obsolete for many years now, and we have been relying on sourcing old stock at very high prices.

We sold the last of our current stock in July 2023, however, I have just managed to obtain a small batch of genuine new RHP bearings from the one supplier in the country who holds some - but they know how rare they are and therefore the price is very high - I am sorry this is the case, but there are no alternatives - and actually I have managed to negotiate and maintain the same price they were last offered at in 2022.

I am told these will not be made again by RHP (these are 'New Old Stock' which is quite usual for bearing suppliers - who always hold obsolete bearings in 'new' condition) - so once they are gone, they are gone.

Note: these bearings were originallly supplied in greaseproof paper in 'rolls of 5' - see the photograph of a previous batch we supplied, which were supplied to me in that way, in the old 1970's yellow RHP box, which we then split up.  Just like this latest 2024 batch, it is standard practice for bearing suppliers to unpack the rolls of 5 bearings - and wrap them individually in a plastic bag and a bearing box - as these are done.  This latest 2024 batch have been supplied pre-split into individual boxes - the box is marked 'HOF' (referring to the old makers name - Hoffman, but the bearings themselves are marked 'RHP', so  rest assured they are the genuine article!

Additional Information on SOHC (and early DOHC) Bevel Bearings:

Because they have not been available for many years, whatever stock is still out there is very expensive to obtain - the bearing suppliers know this!   So worth noting - for the top bevel housing, it is possible to use a single row 'none self centering' replacement of the same dimensions, which I can sometimes also supply (see Item 0006), however, it is really important that the correct twin row bearing is used on at least the bottom housing . . . failure to do this could mean you canot remove the cambox with the engine fitted in the frame! And if you can afford it, it is best to go for this bearing top and bottom.  You must accept though that if fitting a (cheaper) single row, non self-centering 0006 bearing in the top - movement off verticle of the cambox when removing from a frame may be slightly more restricted.  Both do the same job once in place though.

Final hint on fitting these bearings (because at the cost of them you dont want to waste them!!): I have fitted these bearings into housings many times over the years and I have found it is very important not to knock the inner bearing, or accidentally press it excessively, so that the inner race pushes 'out of centre' to the point where the balls totally lose touch with the outer race. Although the inner race will allow this . . . even with a brand new bearing, it is possible when pressing the inner race back into line that one of the small balls could be pushed out of its bronze cage - and be very difficult to get back in place, particularly if the bearing is now mounted in the bevel housing with no access to the underside. Therefore the message is - handle with great care!  It is also very important to fit the dished washer (Item No. 0007) under the lower bearing - which was designed specifically to capture any errant balls that do drop, so as to avoid them dropping into the bevel box and crunching the gears.  My old mentor Titch Allen told me that this design and bearing kept Norton's Service Department in business for many years!. Finally, whenever stripping the engine down, it is always worth checking this area (and bevel box) to make sure no loose balls have made their way out.  The best advice I can give is - always handle with care and never take them off centre any more than absolutely necessary!

- Unfortunately the original type Twin row self centering bronze caged ball bearing is now obsolete and no longer easily available (item no 0005), therefore extremely expensive. I can also supply this single row (non self centering) variety, also manufactured by RHP, as a cheaper alternative to fit to the  TOP cambox bevel housing only, instead of the original twin row type.

The bearing still performs exactly the same function - but as this bearing has a fixed track (i.e. it is not of the 'self centering' variety) it means the vertical assembly is slightly less flexible, and therefore more fiddly to remove the cambox when the engine is in the frame.  However, I have been told by other Norton friends and customers in the past that it is a comon/cheaper replacement and does still allow some movement.  

NOTE: this bearing should not be fitted in the bottom bevel housing, where it is essential the original twin row self centering type is used. Please bear in mind that if using this bearing in the top housing, you should be very careful not to move the cambox off centre any more than necessary when stripping down, as it will force the bottom bearing off centre 

Update April 2020:  Almost as hard to source now as the original twin row bearing 0005 (although normally much cheaper when I can get them), I have managed to obtain a handful more of these as well.  However - if you can afford it and we still have them in stock - I would still advise buying 0005 in preference to these, as they allow more movement when removing the cambox.

This listing is for the original fitment - Single row roller bearing in C3 size from RHP.  RHP are the top quality UK bearing supplier that originally made this bearing, and before becoming RHP were called Hoffman (which may appear on some original bearings when you strip your old engine down).

This roller was fitted to all SOHC engines, both International and early Manx, on the drive side and was innermost to the crankshaft.  This original 'C3' Version is a slightly looser fit than the standard tolerance bearing - as original crankcases were made to take these crankcases on an 'Interference' fit, and once they had been 'shrunk in', the bearing would still be easily spinning - important for a racing engine with minimum Run-In time available.

Unfortunately the original RHP type have been obsolete for many years and now unobtainable.  We have been sourcing the dwindling supplies for many years - but these have now dried up.

Therefore, these are now the options we can offer:

1. This bearing by Special Order : My bearing supplier does have access to a handful of the original RHP C3 still - and the price here is the Retail price they will be as at Febrruary 2021 (but this may change when order is placed). If you still wish to purchase one of these - place the order here as normal - we will confirm if the bearing is still available and if the guide price shown here is still correct.  We may require a deposit to commit on this item.  Sorry the price is horrendous - but that is the position with those original bearings

2. Still Fit a high quality RHP brand Roller bearing, but in Normal Tolerance (i.e. Non-C3) Size:  This is now the most logical solution for many owners, and the one I will be taking myself for future SOHC engines. This 'non C3' version is also obsolete, and the price of those left is also very high, but we do have a small quantity of these still available in stock (see Item 0019B).  These are still made by top manufacturer RHP - and just the same high quality, but you need to give a little more thought to 'running in an engine' when fitting this type, and maybe consider using 'bearing fit' compound when fitting them if your crankcase journal is getting worn - as so many original crankcases now are.  However, a counter argument I have heard said by knowledgable Norton engineers is - as the original 'Interference Fit' on the crankase journal gets reduced by successive bearing change - so the requirement for C3 bearing tolerances also dimishes!  I will let you decide.

3. Fit the Original Lipped Roller C3 Fit from a Cheaper Modern Bearing Manufacturer:  There are also some limited quantities of cheaper (normally 'Offshore' manufactured) versions of the original C3 type bearing.  Update Feb 2021: We are talking to our specialist bearing supplier about a small batch of these.  Email for details: sales@racingvincent.co.uk 

Single row roller bearing - fitted to the inner of the two driveside mainshaft bearings in the crankcase on all SOHC engines, both International and Manx models.  This listing is for the Non-C3 (standard tolerance) version of the high quality RHP brand, as the original C3 tolerance are now unobtainable. 

This roller bearing can be found in both lipped and un-lipped type, these are the un-lipped version.  It does not make any difference which type is fitted - but obviously you must ensure you fit the original inner mainshaft spacer in place - between roller bearing and ball bearing - and ensure the spacer results in the roller inner race sitting approximately central in the outer race (this can be done before assembling the crankshaft, by just placing the spacer in place on top of the ball bearing with the drive side crankcase lying flat, inner bearings sitting uppermost).  It is always good practice to have the roller inner race running as central as possible to the outer race, while ensuring their is some positive clearance between inner side of roller and flywheels, once the crank is locked to the timing bearing.

We also sell driveside mainshaft shims (Item 0262 and 0262b) for this purpose

Background on the difference between 'C3' fit and 'STD' fit bearings (these bearings are 'STD' fit):

If you have already looked at the detail description for Item 0019 (and if you have not already done so - we suggest you read the bearing background in that detail listing)- you will know that the original fitment in Norton SOHC engines was this same bearing - made by RHP or their predecessor - Hoffman, but in a looser 'C3' tolerance. 

These 'C3' fit bearings from RHP have been obsolete for many years and remaining supplies held by bearing stockits have been virtually used up in the last 15 years, with our last stock being sold in 2020.  Theye are now virtually unobtainable (although I may be able to obtain a small quantity by Special Order - but at an extremely expensive price) - but instead can still offer these RHP 'Non-C3' tolerance version.

These are still manufacutred to the same high quality by the original RHP manufacturer, but slightly more care should be taken when running in your engine after first fitting - to allow the bearings to bed in, as they will have a fractionally tighter tolerance than the C3 version.

However, I have also heard a counter argument from other well known Norton engine builders that says - as original Norton crankcases have nearly always had replacement bearings fitted over the years - so the crankcase journals start to loose their 'interference fit' tolerance, and therefore the need for fitting 'C3' type bearings also diminishes.  I can see the logic to this argument - particularly as many Norton original engines used to spin their bearings anyway, but I will leave the choice with you.  However, I know for my part - I will be fitting this bearing into any future engines I build for myself, and just ensure the crank spins freely and the journals are in good condition on engine assembly.

As a final point - many owners over the years did not know that Norton engines were originally fitted with C3 bearings (or sometimes called 3 spot bearings in older times - as sometimes the outer ring of a C3 bearing had 3 dots stamped on it) - so you may find that your engine has already been re-fitted with 'Std' tolerance bearings anyway, and the tolerance difference is minimal.  Normally if a bearing does not have 'C3' or 3 dots ground on the outer ring information, it is a standard bearing.

Sorry these are not cheap - but as at Feb 2021 these are now obsolete too and are getting just as difficult to source as the C3 type.  Therefore the price I am having to pay to source them reflects this.  Again - the supply is also very limited . . . and once they are gone they are gone! (the minimum batch quantity for RHP to make a new batch would be prohibitive for us).

We do occasionally get stocks of these bearings from cheaper (normally 'offshore') brands.  If you are prepared to use non-RHP brands, email us on sales@racingvincnent.co.uk and we can confirm availability - we normally have at least one of these cheaper bearings available in stock.

Single row ball bearing - Fitted to the outer of the two driveside mainshaft bearings in the crankcase on all SOHC engines, both International and early Manx.  This is the correct C3 (loose tolerence) type, from top quality manufacturer RHP.

Feb 2021:  Sorry to say, that just like all other SOHC RHP C3 (loose tolerance) bearings, these are now obsolete and we are down to our last handful of bearings we have been able to obtain.

Once this small stock has gone I fear we will either have to supply RHP non-C3 type or those from a lesser brand.

Single row ball bearing - Fitted to the outer of the two driveside mainshaft bearings in the crankcase on all SOHC engines, both International and early Manx.  Originally Norton would have fitted a slightly looser tolerance 'C3' fit bearing, but with them now being obsolete, the next best thing is still to take the same bearing - from top quality UK manufacturer RHP - but these being the standard (STD) tolerance.

Jan 2023:  Sorry to say, that just like all other SOHC RHP C3 (loose tolerance) bearings, Item 0018 (C3 version) - are now obsolete and we are only able to get them in occasionally as we find them - however, this STD fit bearing (0018B) is still the same high quality RHP bearing of the correct type, we just recommend that when running the engine in, you give it a few more miles to let it bed in fully.

Like all other original 'Imperial' fit high quality RHP bearing - they are now obsolete and are difficult to obtain - however, much better to fit best quality RHP bearings when we are able to obtain them, rather than a lesser offshore manufactured bearing

By the way - it is worth pointing out - as I sometimes get asked this by customers:  a 'C3' fit bearing, just means it is slightly looser tolerance than the STD fit bearing.  This means (as they are normally fitted into crankcases with an interference fit), that once fitted - they will spin more freely than a STD fit bearing initially.  When used on a racing bike, where less time is allowed for 'running in' this can make a difference . . . but on a road bike - using a STD bearing should not be an issue . . . I would normally just allow 500 - 750 miles of steady running in first (and actually - many old owners were probably not aware of what a 'C3' bearing is, I have stripped many engines and found replacement STD bearings already fitted!).

Single row ball bearing. Fitted to timing side Model 30/40 (International) SOHC engines, in correct RHP C3 (loose tolerence) type, from top quality manufacturer. Now obsolete and extremely difficult to source 

Feb 21 Update:  Like all original RHP main bearings, these are now obsolete and are not likely to be available again once current stocks have gone (I know, as we have consulted with RHP and cost for their minimum batch run for making the correct C3 type is prohibitive).

We have managed to source one last small batch of original new RHP C3 tolerance bearings - listed here, but once this batch has sold there may be no further stocks available.

However, we may be able to obtain 'Standard' tolerance (i.e. Non-C3) type in the future.

Timing Side SOHC Bearing - Background Information:  The aluminium crankcase SOHC version (i.e. CS1/CJ or Model 30/40 International) all used this single row ball bearing on the timing side.  However, magnesium crankcase M30/M40 and later Manx (both SOHC and DOHC) adopted a twin row ball bearing on the timing side - giving additional strength and rigidity and a fractionally narrower crankshaft.  Therefore before ordering these bearings - confirm that your SOHC engine is aluminium crankcase version.  If you have a magnesium crankcase version (i.e. M30/M40 Racing International or Manx) then you will require the twin row bearing which we also supply - Item 0021. 

Obviously, the twin row bearing is not interchangeable with the single row type (and actually is still occasionally being made - so is actually cheaper on our catalog than the single row shown here, even though it is bigger - sorry!).  

Single row ball bearing. Fitted to timing side Model 30/40 (International) SOHC engines.  These are from top quality manufacturer - RHP, but are in a standard (non-C3 tolerance), slighty cheaper than Item 0020.  Now obsolete and extremely difficult to source.

These are of the same RHP high quality as our Item 0020 (which is the looser tolerance 'C3' fit), and are the same bearing - but are in the normal 'Std' tolerance.  Norton SOHC engines were originally fitted with loose tolerance C3 bearings - but as most people know, the C3 are now extremely difficult and expensive to source, and these are slightly cheaper.  For many owners - a 'Standard fit'  bearing is fullly acceptable (and actually - some find their engines had been previously renewed with stanard fit bearings!), you just need to be aware and alllow a little more time for running in (remembering these were originally fitted to race engines - where running in could have been just a couple of laps!).

May 21 Update: 

Like all original RHP main bearings, these are now obsolete and are not likely to be available again once current stocks have gone (I know, as we have consulted with RHP and cost for their minimum batch run for making the correct C3 type is prohibitive). For these particular bearings - i.e SOHC International Timing side, as at this point, we have been able to obtain another small batch of 0020 (C3) fit bearings, but knowing they would quickly run out, we were also able to obtain a batch of these non-C3 fit at the same time . ... as both are now obsolete, we decided to get both types now, while we still can! 

Timing Side SOHC Bearing - Background Information:  The aluminium crankcase SOHC version (i.e. CS1/CJ or Model 30/40 International) all used this single row ball bearing on the timing side.  However, magnesium crankcase M30/M40 and later Manx (both SOHC and DOHC) adopted a twin row ball bearing on the timing side - giving additional strength and rigidity and a fractionally narrower crankshaft.  Therefore before ordering these bearings - confirm that your SOHC engine is aluminium crankcase version.  If you have a magnesium crankcase version (i.e. M30/M40 Racing International or Manx) then you will require the twin row bearing which we also supply - Item 0021. 

Obviously, the twin row bearing is not interchangeable with the single row type (and actually is still occasionally being made - so is actually cheaper on our catalog than the single row shown here, even though it is bigger - sorry!).  

Twin row caged ball bearing. Fitted to Model 30M/40M (Manx) SOHC engines in original C3 looser fit, from high quality SKF manufacturer.  

This is the twin row bearing fitted to the timing side of SOHC magnesium crankcase M30/M40 (i.e. pre-Featherbed) Manx models.  It is different to the aluminium crankcase International models timing side bearing (which is only a single row bearing) - making the M30/Manx models stronger in this important area (which may explain why pre-featherbed M30/Manx magnesium crankcases are often found with the drive side crankcase damaged but timing side ok).

Original bearings had steel/bronze cages, but have not been available in that form for many years.  Modern versions of this bearing are now supplied with a nylon cage.  This is the correct looser fit 'C3' bearing as fitted to original models - but bear in mind the cage is nylon when soldering the whitworth screws over the bearing retaining plate - particularly if using a blowtorch, do not get the heat too close to the cage!

SKF is a high quality manufacturer of the same qualithy as RHP manufacturer, and now very difficult to find.

Update April 2020: For the last 5 years this bearing has been getting progressively more difficult to source, and back in 2019 we ran out of them completely.  I have marked this listing as new again - to highlight to customers that we have managed to source a small quantity of this bearing from high quality SKF manufacturer in the correct 'C3' looser fit size (as originally fitted).  although not cheap - if you have a magnesium crankcase M30/Manx, these are the correct bearing and not sure if they will be available again when these have gone