Engine identification required

http://classicenglishbikes.com/tech_file/norton.html

Yours looks about 1947 vintage.  Someone has enjoyed a nice machine.  10M on the frame declares a Model 40 (350cc).

Looks like magnesium cases, consistent with Manx type.

Looks like a nice used machine...   try  keep  it  that  way

J

The logbook number suggests a 1947 (letter B). The 10M suggests a model 40M Manx 350. The serial number 10096 is in the 1947 range. So the original engine was a doubleknocker.

What your engine actually is I don't know, but maybe a pre war one. A cammy (SOHC) 350 engine with probably magnesium alloy parts. The TT9 also might be pre war.

It is fairly common that old bikes used for racing got a lot of transformations.  An original race bike is a very rare bird. Hopefully you will get better answers from our wiser members.

The club holds factory records for this period. I suggest that you go to "records" on this website where you will find information about how to obtain a dating record for the frame and engine.

Hi William,

   Your frame and engine look correct for a 1947 350 Manx, and the number 9326 could be a shop frame number for production reference. The frame number should be on the left side of the front petrol tank lug, or possibly the front engine lug. The engine number should procede the 71 x 88, unless the crankcases have been replaced and not stamped up. Both these numbers should be the same if they are from the same machine. The DOHC engine wasn't available to private buyers until the latter half of 1949.

   Looking at the other parts on the bike, it could have been built up from spares. The gearbox is the early post-war road spec type and the oil tank is also road spec. The carb and the mag are both as used on the standard Inter and would have had a dynamo fitted for road use. 

   As Tim says, your best bet would be to get a factory record, but your will need to find the frame and engine number first.

with some variations from what one might expect as a 'catalogue' machine.  The coding B10M is exactly what I would expect for a 1947 350 Manx.

I would say that the engine is mostly Manx, but the cylinder barrel looks like an International one - it appears to lack the 'square' top fin and rapidly tapering to round of a low-case long-stroke Manx.  The upper bevel cover plate is for cam-centre oil feed, but is alloy, I would expect it to be magnesium. Some Inters got alloy cam-box and magnesium bevel plate. The cam-box is magnesium, and not machined for a decompressor.

Having said that, this could be one of the very first Manxes made. (Pedant note - the 1939 customer racers were 'International Nortons to Manx specification', and were not 'Manx Nortons'.) The factory may have been short of parts, and eager to get machines out the door to customers at the IoM, and used what they had.

I would say tidy it up and get it running. If you take it to an event or two in its grass track form, it may attract attention from old-timers who may remember how it was done 'back then'.  You may find out about first-batch Manxes and grass tracking mods of the day. 

It would be really interesting, and help with identifying what you have

- that front brake looks like a roadster iron half-width hub with a Manx sls brake plate (it looks like alloy, not magnesium) fitted to it.  But Norton did not do an iron 8" front hub then.  Is it 7" or 8"?  Curiouser and curiouser.  The first Manxes got iron rear hubs.

The cylinder barrel is definitely Manx, not an alloy International one.

It's a lot tidier than you suggested earlier.  I would suggest sorting out its obvious defects and go for a ride.  It probably needs a rear chainguard, functional lights (if you go all-LED, a battery only will do for a few hours' night riding...) and a registration plate holder. 

Is on the top casting on the seat post. Often upside down.  I have it on both my plunger frames, so I believe it to be a part number for that casting.   That is a full on Manx spec frame, with the “V” cut lugs and window tank and engine lugs.  As Paul said this is a very neatly turned out machine. Not a million miles away from ready to ride. .  Many interesting features that I’m sure the specialists will pick up on.

You have the necessary documents to register. It predates requirements for testing so if you feel confident to go over the basics and necessaries I would get a few miles on it and then work out what to do about authenticating later.

 Very nice find :-))

J

Footrests are a possible issue.  Left side is on the rear set lug, with rear set brake lever.  So it either stays there, or move it forward and you need a standard brake lever.

The right side rest seems to be missing.  If you put it on the rear lug, you'll need to sort out the kick-start.  The gear lever is set for a forward footrest which then allows the kick-start to stay as it is.

Original tinware (primary chain case, chainguard) will be hard to find.  It might be worth approaching one of the restorers first.  Lots run with only the top cover on the primary.  It looks hazardous...keep fingers away and wear decent boots - and don't get your trousers caught...

Rear chainguard protects you from a chain break, and protects the machine from chain lube being flung everywhere.

It would be a shame to keep it off the road for want of the correct tinware.  Beyond that it's your call.  Summer is (we hope) approaching.  Not the best time to have the bike off the road.

Dynamo would have been removed for racing.  LED lights mean you now longer really need it just to get home late.  Some riders do big mileages with total loss LED lighting.

I'm lazy - I'd add red coachlines inside the black on the tank, and some proper Norton transfers, add a top chainguard and get it on the road, sort out footpegs and see how it behaves.  Then you'll find out if it's mechanically sound, or if it needs mechanical work.  Next winter will be the time to do the complicated things.

is to ease out those rusty front engine bolts, clean them and put back with some grease. 

If it goes like some of my efforts , now may be the only time you get to ride it. All too easy to pull apart and create another basket case. Change oils ,do some fetling  and safety inspections and get some riding in.  You will soon find enough to do.

Hi William,

   I thought you may (or not) want more observations on your new aquisition. I believe your frame is a later replacement as it has the later "V" section plunger suspension castings which were not in general use until the 1950 season. You might see earlier bikes that have this shape, but these have been modified individually. All the other features pertain to the 1947 type frame. This may be the reason why there is not the correct number stamped on the frame. 

   If the engine number has been removed, it may be possible to find trace stress pressure marks by chemical identifying process, although that's probably a step too far. These crankcases were used from 1936 until 1947 and the big fin head and barrel from 1939. The number 9326 on the frame would equally be a 1939 350 engine number as they had their own number series pre-war.

   Paul is correct regarding the front hub. This is a 7 inch iron hub as used on racing Internationals from 1934 to '36 before the introduction of the 8 inch conical hub for 1937. The hub is finned for cooling and slightly wider than the road spec type. The aluminium brake plate is correct and has magnesium brake shoes which have forked ends and pivot on a single spindle.

   The petrol tank looks to be a 1950 DOHC aluminium type and the clutch and brake pedal are the correct Manx items. You will need to get some Norton books with photos of original machines if you want to make it a race bike, or build the bike with what you have for the road.

   If you have got a V5c, I wouldn't bother chasing the numbers too much.

The primary chain appears to have little or no slack. Not good for engine or box bearings.Check the Box fixings are ok. My 36 bike had some poor substitutes that allowed the box to pull back and did some mischief to the main bearings.

Also check primary slack when fully warm. Anyway on later Manx. On the one I now own, chain broke at last lap in -63 Junior TT.

Thank you for posing this article, the responders are every knowledgable and we get to learn a bit more about the development of the Norton.    

As you are bike savvy, (you must be if you are a Velo man… :-).  ) you will already be aware of the required adjustments; both chains are well tight and the rear spindle nuts not home. The rear brake return spring needs to be set the adjuster setup is a bit unusual for me, it limits the amount of pressure you can apply but in off-road use that may be an advantage.

 The frame has an Andre damper anchor plate, which I thought was dropped by 1950?  The bars look to be Triumph TR style, whatever they are a good shape for off-road. 

As Richard says the front brake would be pre 37 and the shoes would be 1.5” wide.  I guess you have a collection of bits that came with the machine as some of it is not consistent with the current build state. Single feed banjo with twin tap tank. Mag Dyno but no regulator, (dynamo drive plated off).   Your fuel enrichment device on the carb is locked off to a fixed position. It works opposite to a choke but acts on the primary circuit not strangling the air flow.  It’s a 1938 version of the 10TT carb.

It has its own story which you should try and investigate, it’s far more interesting than a factory finished example.  The pegs and levers are as they should be though as per David’s comment kickstart will me an issue.  Norton did a folding foot peg for this scenario but you can easily fashion one from a pillion peg.    

It is a nice machine and look forward to hear of your progress with it 

Best regards

Jon

If you take a look in there you will see yearly brochures of the models and can pick out some of the major changes.  They are not always accurate but you get a feel for the differences.  Hope this helps.

Jon

the so-called 'doll's head' is the pre-WW2 road gear-box.  It had a round-ish cover over the positive stop mechanism, and the clutch quick-thread lifter arrangement was external.  Post WW2, the gearbox outer cover was changed, so that the outer cover was oval and covered the positive stop, the clutch lifter and went around the kick starter as well.  This is the gearbox you have, which I am guessing is a close-ratio International box. 

If it has a high-ish first gear (27-14 tooth), and a HUGE jump to second, and then close 2-3-4 ratios, it's an Inter box.  If so, converting to Manx spec means getting a race-type end cover (it keeps the doll's head look, and as far as I remember, kept the external clutch lifter) and a different first gear pair 25-17 tooth.

Just for a little extra confirmation, those Roadholder forks are Manx.  The sliders are the early type with the mudguard stay bolts one above the other, directly above the lug for the Manx brake plate.  It lacks the lug for a  roadster front brake. FWIW the iron-lug frame Manxes kept this early Roadholder style fork slider right up to Featherbed Manx.  Manx ones are forged, roadster are cast.

The first couple of years of road bikes (1946-48 ish) had a slider that looked just like this, with a lug for the roadster brakes as well (the Manx lug was not machined..)  Should you be in need of a pre-fetherbed Manx slider, then an early road one will do at a pinch, machine the unused Manx lug, and cut off the road brake lug.  My 1955 Dominator has the un-machined Manx brake lug, but '56 bikes did not.

Footrests - road Inters mounted them in the same way as any other road Norton, using a long stud passing between engine and gearbox. From memory the footrest arms are a little longer to move the rests backwards a little.  Now there's a good idea, I should do that to my Dominator......  The road Inter frames came with extra lugs to mount the same footrests in the rear position as on a Manx.  You do not get the fittings to use the front position on a Manx.  You could get some Inter engine plates and a kit of footrest parts if you are really determined.  You will need to change the brake pedal and gear lever as well.

A 1950 Norton Singles Parts book (Model 7 Dominator got a separate book) will be useful, that was the first one published by Norton post WW2.  You may get lucky and find one on the net.  Bruce Main-Smith used to do photocopies of such things.  Should you be desperate, I have a '50 Singles parts book which could be photocopied.  You should also get Norton's Maintenance Manual which covers the plunger International and early Manx.  I just had a look in my copy, it has notes in it made by my father in 1954 or '5, with an annotation pointing out that Fig 4 on page 11 has an error - it shows 12 vernier holes on the inlet cam, same as the exhaust.

Detailed information, the 1950 Spares manual is also available in the library section. Online version.  I think the MagDyno is not correct for an Inter; it is tight cable advance and should be slack ( the manual cable is on the wrong side). But if you want to turn I into it’s Manx origins then Lucas or BTH magnetos were offered.

Enjoy!

Hi William,

   Your gearbox with the small round access cover will most likely have standard gears which are preferable to the close ratios for every-day riding. The access cover was modified to the oval type for 1947. You can fit a non-kickstart racing end cover to your casing, but you will need a layshaft to suit. 

   The reason your lock stops don't line up is because you are missing the round chamfered edge stops that fit on the protruding bolts. The reason for these was that Norton used the same headstock as that used with girder forks and the round stops were a cheap solution. I think these are available from the NOC shop.

   I have attached a scan of the parts book that will be the most suitable for your bike. Also there is some good info on Ken MacIntosh's website at    www.postwarnorton.com

The gear ratios were stamped on the rear of the gearbox casings before the war.  Both on Inter and the other road bikes.  Post war I believe they only stamped the Inter, but might be wrong. It's worth a look.

If you have the Inter ratios, RGM sell the "Daytona" first gears. A higher first gear closes up the jump from 1 to 2 and makes it much more road friendly.

The Dommie version of malleable iron casting for the footrest hanger will fit.  The actual Dommie peg is only a plain bar but it will unscrew to allow the proper footrest to be added.

1.77 is the bottom gear for non- kick-start Inter.

Hi William

Great looking bike, and will make for an interesting project.

if needing any inspiration attached is my road registered Manx/Inter special built in 1951, pre war engine, late 40’s double knocker Manx frame.

as many on here have said get it all safe and out on the road.

regards 

Simon

The gearbox on Simon Carver's bike is the Doll's head box.  This was used from 1934 when the Sturmey Archer gearbox became the Norton box, made by Burman. This version continued until some time in 1947, when the slightly improved 'vertical' box was introduced.  It had a larger vertical oval cover encompasing the positive stop, clutch lifter and kick start boss.  The kick start lever return spring remained under a removable cover.  This is the gearbox on William Monteith's machine.

The racing gearbox, as on Manx and Clubman's International had essentially the same end-cover as the Doll's Head box, but lacking the kick starter boss area. Note that the clutch lifter arm is external.  This end cover was used on all plunger Manx machines. The advantage of a proper Manx gearbox outer cover is that the layshaft ran in a ball bearing set in the gearbox end cover, instead of a bush inside that kick start shaft.

The featherbed Manx adopted a version of the 'horizontal', or 'laydown' box - also made by Burman for Norton.  I suspect that it was machined from the same castings as the road box. 

For details of finishes, you need Bacon's 'Norton Singles'

Rims would be chrome with black centres and red coach lines.

But although 21" ribbed front tyre is still made by Avon (unless they stop later this year....) the 20" rear tyre is not so easily found (except for off road machines). You might be better off with 19" rear and 3.5 section tyre than the correct 20" rear and 3.25 tyre.  The Featherbeds all had 19" at each end.  So check if you can find the correct tyre before you put time and money into wheel rims.

The lug in your second picture has the scallop shape cutaway of racing frames. Saving weight and perhaps improving brazing penetration inspection.

Hello NOC I bought a 99 dominator in Birmingham 10 years ago, I drove with many miles without problem. But after a engine trouble I opened it . I thought it was a 600cc but not it's a 500cc

Can you explain this transformation to me where is it original ? N° frame M14 73201 and N° engine L14 69013 and on the rear crankcase 99 1284

Thank you all

There is no dimensional difference between 88 and 99 crankcases ,cylinder heads and connecting rods. Its only the cylinders, pistons ,cranks,pushrods, carbs and gearing  that are different. This makes it easy to swap whole engines and build mongrel engines . No one at an Mot station or Tax office would have a clue that changes have been made . It was usually done to avoid expense and use locally found spares. Just live with it. But be aware that some mixtures will need modified parts to avoid mechanical mayhem. If you have such an issue you would know all about it by now !.