The 1931 Norton brochure

Sent by Wim

The Franks redesign of 1931

By Simon

The Franks redesign which resulted in the 1931 range of production Nortons was not an unmitigated success! I have already mentioned my late friend Jack Bindley's experiences with his new '31 ES2. He was as disappointed with the bike as he was with Norton's response to his complaints. Last week I came across a few back numbers of the Beaulieu magazine 'Veteran and Vintage' and found further criticism therein from Richard Chapman, who worked for Eric Fernihough (amongst other well known people) at Brooklands in the thirties. Richard bought a new 1931 Model 18 from dealers in Trowbridge, to which, after careful running-in, he attached a new TT Hughes sidecar. He goes on to say..

"This machine was the slowest thing on wheels and a great disappointment. With the light TT sidecar and a passenger, the maximum speed was about 50 mph and after a while I rode the machine to Birmingham to see the makers about her. A tester took her for a run round the houses and reported that she was up to standard, which drew from me the comment that their standards must be pretty low! After a lot of postal haggling, Nortons gave me a set of what they described as 'dirt track rockers' (ie cam followers) for the crankcase and these improved matters a little. I then got going on my own and raised the compression. I increased the inlet tract bore, fitted a larger inlet valve and a 10TT25 carburettor. This, with stronger valve springs, rebalancing and some work all over the engine, improved matters. The final result was that I could get 80 mph with a passenger in the sidecar, under reasonable conditions."

Richard must have had considerable tuning skills - doubtless enhanced by later experiences with Fernihough.

The reference to Dirt Track Rockers is intriguing as the dirt track model (above) was only made in 1930 - not '31 - and it would be interesting to know just how the rockers differed from the standard profile. And there is a possibility we can find out: a 1930 dirt track engine bottom end has surfaced in NZ and although rather hacked about, I am encouraging the owner to take it apart and see just what is inside! So watch this space!

The decline actually seems to have started with the 1930 enclosed rocker box set-up. The geometry of this rocker box is such that the valves open less than the lift on the cams while with the open rockers they open more...And why did Norton dowtune these engines? My guess is that they were seeking longer term reliability. What else could it be? From a marketing (doubt if the word had been coined then!) point of view it was perhaps no bad thing to have the OHC machines as real flyers and the over the counter bikes as just reliable moderate performance means of transport.

1931 Model CS1 Norton - Sold

Sent by Alf. From the April 2011 issue of The Classic Motorcycle.

Don't bother contacting Marco, it's gone already.

Colin's 1931 Model 18 Norton

Colin in the UK sent me these pics of his '31 Model 18; note the left-hand exhaust, Enfield rear hub and Sturmey Archer four speed gearbox.

In addition he sent a few photos (below) of a c1931 four speed positive stop mechanism that he picked up recently. Does anyone recognize the part? Is it a fitment to a vintage Sturmey Archer gearbox? Please let us know, Colin would like to fit it to his Norton. See this blog entry for more info.

1931 Model 16H Norton

Not the most exciting Norton ever made but an interesting model anyway. This is a 1931 Model 16H, still with the  Enfield rear hub and Horton front hub. The first year to have the magdyno situated behind the barrel, dry sump lubrication, Sturmey Archer three speed gearbox. In quite original condition (apart from perhaps the front forks that may be from a later model) and for sale at Dutch Lion Motorbikes.

Max's 1931 Model 20 Norton

An email from Mike Slater

"Thought you might be interested in this pic; this is my great uncle Max's bike, pictured in 1939 (at least the license plate makes it pretty easy to date the photo). I don't really know much about the bike, apart from the fact that it seems to be a Model 20, with what looks like an aftermarket suicide shifter fitted and the tool box removed."

JdK: It's a 1931 Model 20 Norton. Note the twinport exhaust, the position of the magdyno behind the cylinder, the Enfield hub at rear, the Horton hub at front and the early Norton forks (without the typical Webb wing nuts). An interesting feature is the instrument panel mounted on the front forks. The gearbox lever for the Sturmey Archer box is original, as is most of the rest of the bike.

1931 CS1 Norton

This CS1 has been advertised on Ebay for a while now and what follows is the description by the seller: "According to the Works Records this Norton left the factory fitted with a close ratio gearbox, racing magneto and racing carb, all of which are still there.When I bought this machine 10 years ago it was fitted with a Honda tank and Suzuki wheels. I have found and fitted the hand-made steel tank (which needs major welding) that was fabricated by the man who raced this bike with some prominence in the 1930s. I have found and fitted an original oil tank. I have fitted a correct front wheel and a period correct rear. Also fitted are a correct Andree steering damper and solid control levers. The engine and gearbox appear to be in excellent condition. Bidders should be aware that this bike was raced continuously from it’s delivery date up to the ‘60s so deviation from standard spec are to be expected. I have a lot of pictures of this bike as it was raced at Daytona, Langhorne and Savanaah in 1935, already a 4 year old machine it lapped Langhorne at over 83 mph beating factory Indians amongst other current race bikes."

A very nice Norton and an appealing story but there are a few issues; the page in the Works Records (below) where the entry for this CS1 should be has been damaged and while the gearbox (as fitted to this CS1) is listed, the numbers for the frame and engine are missing. While the framenumber as used by this CS1 could be correct, it is also a bit high to fit comfortably within the sequence as in the records. Further, as indicated by the vendor, many parts have been replaced since the Norton left the factory.

Is this a problem? Not for the Norton, it will be a very fine bike once it has had the attention that it deserves. The problem is that the story comes with a price tag and I would be worried about finding a next owner willing to pay the extra money for what's basically a few black and white photographs and a torn piece of paper.

The 1931 TT races

Photos by Howard, research by Simon

The winners of the 1931 Senior TT; Tim Hunt (number 46, who came 1st at 77.90 mph), Jimmy Guthrie (number 44, 2nd at 77.34 mph), Stanley Woods (number 38, 3rd at 76.35 mph); all riding Model 30 International Nortons.

The woman with her hand on Tim's shoulder most probably is his mother. The man with his hand on Jimmy's shoulder, wearing the hat, on his right is Nigel Spring who entered him for the race. Arthur Carroll is behind Woods, his head is above his right shoulder.

The photo below shows Hunt again, the winner of the '31 Junior on his Model 40

Sven's 1931 Model CS1 Norton

An email from Sven in Sweden: "I found another old photo of my CS1; my father, mother and sister (sleeping in my mother's arms) are going for picknick in the summer of 1948! Note the left-hand side upswept pipe without a silencer!"

1931 Model 20 crankcases wanted

An email from Albert in Malta: "I wonder if you could help me? I gave my 1931 Model 20 crankcases for welding as I discovered some hairline cracks around the bearing bosses. The "professional" welder I gave them to managed to ruin them for me (he did not normalise the cases prior to welding) and they are now useless, as they cracked up when cooling down. Do you know anyone who might have a spare set for sale? 1931 and 1932 Model 18 are similar. Best regards, Albert"

Anyone who has a spare set of cases or an engine  for sale can contact John and I'll forward your message to Albert.

1931 Model 19 Norton outfit

Clearly a 1931 model; it has the magdyno behind the engine but the front- and rear hubs are still Horton and Enfield respectively. No cradle frame and as it is hitched to a sidecar it's likely to be a Model 19. The black-out mask suggests a wartime photo.

Overhead Sidevalve Norton

This Norton is for sale at Yesterdays. At first glance a normal sidevalve 16H Norton but when you look more carefully you'll note that the inlet stub and the exhaust pipe are not where they ought to be. Some clever modifications went into this engine, apparently in the way the valves are situated.

The engine was discussed in several issue of Old Bike Mart and above is one of the suggestions as to how it could work. In this setup, the valves are opened by the valve springs and closed by the cams. A flaw in this design is that tappet clearance is still required (metal expands when it gets hot) and as the valve springs open the valves, the valves will not close completely unless forced to do so by the cylinder pressure of a running engine. 

This very nice drawing (above) is another suggestion as to how it could work and frankly, I don't get it; there is still a provision for tappet clearance but now the valve springs close the valves; I don't understand what opens the valves unless these "yokes" could pull the valves open in the presence of tappet adjusters.

The photos above show how it actually works in this Norton's engine; the valve springs close the valves as in a normal engine but the modified cam followers pull the valves from their seats. The valve seats are in the cylinder head now and the valve heads are reversed, as predicted.

So what problem has been solved? In my opinion no more than a slightly more efficient gas flow; less bends to take and perhaps a little bit more performance! On the downside, there is a lot of ''play'' in all the parts that move the valves around and it is hard to envision that this engine will be either very quiet or rev like a proper OHV machine.

Thijs of Yesterdays assures that the machine runs very well, and it looks looks like a lot of love and care went into it's construction. A real opportunity to buy a truly unique part of motoring history!

An envelope

Another contribution from Martin in the USA:

"This is the back of an envelope I purchased several years ago. It was mailed from Tallinn, Estonia (a country in north-eastern Europe) on October 31, 1935. It was sent to the RCA Victor Company, Inc in Camden, New Jersey, USA.

Has anyone ever heard of Mr. Freybach? Maybe a racer or "local hero"? According to Google Translate, "masinate kauplus" means "machinery shop". Maybe he was a dealer or motorcycle tuner of note? Whoever he was, he went to the expense of having his envelopes personalized." 

The motorcycle appears to be a modified 1931 ES2; the magneto is behind the engine but it still has the Royal Enfield rear hub and the exhaust pipe on the left hand site.

Discovery of a 1931 Manx Grand Prix winner

Mr Jock Muir (above) was a student at Cambridge University and came from Radlett, a small town close to Luton in Bedfordshire. Jock raced Velocettes with a great deal of success. At one point in the 1930 Junior Manx Grand Prix he was second to Freddie Frith and he settled the fastest lap before retiring due to mechanical problems. In the Senior race he finished 5th, mounted on a 350cc (!) Velocette!

It's a fair bet that agents ‘Dunham and Haines’ supplied Jock’s Velocettes. Dunham and Haines were in Luton, very close to where Jock lived. With Jock’s performance in 1930 they managed to get him a works Norton to ride in the 1931 Manx Grand Prix; the Norton factory supplied their expensive works machines to successful riders only. Sure enough, there is a note in the Norton factory dispatch records that a specially prepared CS1 model with engine number 51750 was delivered to Dunham and Haines on the 26th of August 1931.

Jock did not disappoint Norton and won the 1931 Manx Grand Prix on the CS1; the page above from the 1932 Norton catalogue “That brilliant motorcycle” reports on his victory. The photo at the top of this page probably shows him on his Norton during the race. Happy with the outcome, Dunham and Haines displayed the machine in their shop and the photo below shows the Norton on display, along with Jock’s Grand Prix trophy.

Jock continued to race his Norton and was quite successful and photos of him appeared in the 1934 ‘Roadholder’. One has the caption “J M Muir during his record breaking run of over 101 miles in the hour”. He raced against riders like Frith, Daniell and Crasher White and certainly was no slouch.

Then comes a gap of about 60 years when in 1996 a long standing friend of Alf purchases the remains of a Norton from a farmer in Northern Ireland. The machine was in pieces and in very poor condition. It looked distinctly pre war but it had had a swinging arm conversion and a pair of BSA telescopes replaced the original girders. On his friend’s behalf, Alf sent the engine and frame numbers to the Science Museum in London who at that time held the factory dispatch records and the records stated the magic words; the frame number and the engine number matched and the machine was a works special prepared for the 1931 Manx Grand Prix!

It took Alf another five years to persuade his friend to part with the Norton. As the owner, Alf continued his search and wrote to Old bike Mart who published a photo and description of the bike. There were many replies from Luton residents and a note turned up from a Mr Peter Roydhouse stating that a Norton with engine number 51750 had been supplied to Mr J M Muir in 1931. We can only conclude that Alf most probably owns the remains of the genuine 1931 Manx Grand Prix winning Norton!

The engine of Alf’s bike is of a later type than 1931 as it has the timing side rib in the later position and the filter bolt under the bevel housing that was introduced after 1932. It also has a more modern bronze head and a magnesium cam box with a central oil feed fitted. The engine is stamped as per the original number and there are no signs of another number that has been erased. There seems no doubt however that favored customers could and did return their bikes to the factory for up-dating and the fitting of such things as new crankcases, bronze heads etc. so all of these changes may have been made in the machine’s active life as a racer. Jock retired in the 1933 Senior TT so perhaps he wrecked his engine?

Alf started the restoration in 2003. Engine and gearbox (still containing the original close ratio gears) have been rebuilt by now but Alf intends to leave the frame as it is; all part of the bikes incredible history! (Story by Alf)

Rebuilt engine

Finally the engine is back in the frame. New seals in the cambox, new bearings for the vertical shaft, a new gudgeon pin and new valve spring top clips. Bigend and main bearings appear to be OK and were left well alone. I would have fitted new valves and guides if I could have got them in time, they will do for another season. Fitted the BTH magneto.

At least I can start the engine to see what it does, no disasters should happen.

Rikard's 1931 CS1 Norton

Rikard bought his CS1 norton new in 1931 at the age of 20 and kept it untill he passed away at the age of 69. The pictures above were taken in 1931, 1946, 1953 and 1969 respectively. Read the whole story on Paul's blog!

The CS1 Works records

The VMCC archive holds the original Norton works records. These records can be searched for data regarding your Norton's engine and frame numbers. This results in extracts as depicted; the one below is for the CS1's frame (frame No. 446xx), the one above for the engine as currently fitted (engine No. 53742).

Clearly, the engine left the factory in another frame, but, the frame is a genuine 1931 CS1. The engine may be from a CS1 or a M30 International but that's hardly relevant as a later cylinder head has been fitted. The record for the frame indicates that the bike left the factory as a special, sporting a specially tuned engine, foot change and a right hand exhaust. I really like the remark about "tuned for monoplane fuel" which indicates it must have been fitted with a seriously high compression piston. This confirms again that the Norton factory was very easy on what they sold to the public; whatever you wanted and paid for you could have, which makes it hard to define what's 'original' or not.

This must have been one of the fastest Norton's you could buy in 1931 when the M30 International still had to be launched. Unfortunately, someone blew up the engine and it had to be replaced. At least it was used as the maker intended!