1934 Norton International

Andy Marks
4 days ago
8 min read

I bought my 1934 Norton Model 30 International on eBay in 2011 as an incomplete project with many major components missing. Rather than restoring it as a museum piece, I rebuilt it into the kind of pre-war road-going racer I wanted to own and ride. This page follows the restoration, engineering work and modifications that returned the bike to regular use

A Brief History of the Norton International

When Walter Moore left Norton for NSU in 1929, Arthur Carroll was tasked with re-designing the OHC (Overhead Camshaft) models. The 500cc Model 30 and the 350cc Model 40 Internationals were first listed for sale in 1932 and were quickly adopted for competition use where they proved incredibly successful throughout the 1930s.

Two vintage racing Norton motorcycles numbered 27 and 3 in front of a stone wall in a black-and-white scene. — A pair of Norton Internationals at the 1936 IoM TT

After WWII, the Manx took over as the number one choice for competition and the Inter, now fitted with plunger rear suspension and Roadholder forks, saw little further development until 1953 when it gained the already proven featherbed frame. However, this only lasted a couple of years as, in 1955, the International was dropped from the Norton catalogue.

My International

I bought my International unseen, on eBay, in 2011. I knew very little about it at the time but took a fancy to it and decided to take a bit of a chance. It was advertised as a 1935 bike and from what I could see the rigid frame and all alloy engine looked about right.

After a conversation with Chris Streather at the Norton Owners Club I discovered that what I had was actually a 1934 frame and 1936 engine. This didn't worry me in the slightest, my plan was never to build a perfect, matching numbers bike for display in a museum. I wanted to build a bike in the style of a pre-war racer and then use it on the roads, this project fitted the bill perfectly so I got to work.

Shown in these pictures is all that was present. Parts that needed to be sourced included wheels, mudguards, handlebars, control levers, brakes, engine plates and so the list went on.

Over the next 18 months I was able to find most of the missing parts and, what I couldn't buy, I made or adapted from similar parts.

The Dry Build

I will say this until I am blue in the face, the most important part of a project like this is the dry build. I had to make, modify and fit so many parts from different sources that getting the frame painted as the first job, although looking nice to begin with, would be a disaster. It's a lot easier to work on a bike when you aren't worried about the paintwork on the bits you've already finished.

Gearbox Repairs

A common problem on Nortons fitted with the 'Dolls Head' and Upright gearboxes is broken lugs on the top of the gearbox. This is caused by excessive wear on both the top of the gearbox and the pivot at the bottom. This allows the mainshaft to twist the gearbox in the frame and snap the lugs off of the top.

Fortunately this gearbox had not yet broken but it was worn, so I had to do something to prevent future damage.

I bored out both the frame and the gearbox to take top hat bushes. I then made a complete set of new fixing bolts to ensure a tight fit and no room for any twisting.

Close-up of a metal gearbox housing mounted in a black Norton frame in a workshop, with tools and parts blurred in the background.

With this one, I used top hat bushes in the top lugs to ensure a tight fit on the frame. If this isn't tight the ears would be pulled in when tightening the gearbox up and, not designed to bend, I'd probably have ended up breaking the ears off.

Since doing this bike, we have carried out repairs on other Norton gearboxes and now do it slightly differently. I've written a technical piece on how we Repair and Modify Norton Dolls Head and Upright Gearboxes.

Wheels and Brakes

The hubs were missing all together but fortunately all 1930s Nortons where fitted with the same ones so they are fairly common and I was able to find a pair. I did however have to make wheel spindles and modify the front brake plate. Most 1930's Nortons had the brake plate fitted on the left, so a left hand brake plate was easy to find. The Inters however have them on the right so I needed to turn the anchor over and move the speedo drive.

Once the bike was on the road the front brake turned out to be woeful. I had a new brake drum made by a friend who was, at the time making Vincent brake drums for the VOC. He turned it from a solid piece of cast iron complete with stiffening ribs around the outside. This gave me a huge improvement in braking performance!

A cast iron brake drum for a 1930s Norton

Mudguard Brackets and Stays

I bought the mudguards from Paul Norman at Racing Vincent. The quality was superb and all I had left to do here was make brackets and stays as shown in these pictures. I purposely left this job until after the wheels, with tyres, were fitted so I could ensure the mudguards followed the line of the wheels properly. Nothing ruins the flow of an early race bike more than poorly fitting mudguards!

Close-up of a rusty motorcycle wheel hub and spokes, with a shiny bolt and axle rod against a dark background.

Metal parts and swaging tool laid on a worn workbench, showing a workshop scene with no people or text. — The swaging tool I made to flatten the ends for bolt holes

I made the top mudguard bracket from a flat sheet of steel. Cut, filed and formed manually, it was very time consuming but there was no point making jigs and tools for a one off like this.

Close-up of a rusty Norton girder fork bolted metal mudguard bracket on a black cylinder, beside a red-green braided cable.

Tank Brackets

These were not available at the time so I had to make one. This is just one example of the huge range of brackets, bolts, fixings and so on that I had to make. It's a good job I have access to a well kitted out workshop!

The rubbers and cups came from Paul Norman, again. He now also does the aluminium brackets, bolts and a huge range of other parts for SOHC Nortons.

Girder Fork Repairs

Four metal girder fork spindles for Norton laid diagonally on a bright blue surface, showing worn ends and hex nuts.

The forks and spindles were badly worn so I bored out the forks and fitted bronze bushes.

This was before the days of Kingpin Components but I still took plenty of pictures and many of them are used in the Technical section of this website. I won't repeat myself here so please take a look at my articles on Girder Fork Repairs if you are interested in this part of the job,

I also made a new set of spindles from EN16. We now have Norton Girder Fork Spindles and other Girder Fork Parts for sale in our shop.

Clutch

Something else unique to OHC Nortons is the narrow clutch. It uses the same plates as all the others but with only 3 friction plates instead of 4. The one that came with my bike was badly worn so I bought a new ES2 one, turned it down to the correct thickness and machined the cutaways in using the indexing head on our Bridgeport milling machine.

I then sent the basket away to be copper plated and the pressure plate was chrome plated. I assembled the clutch using Surflex plates and was rewarded with an incredibly light clutch which works as well as I've experienced on any bike I've ever ridden.

I made new adjusting screws in stainless and put a steel plate behind the pressure plate to spread the load when operating the clutch. I found otherwise the pressure plates in these tend to distort with just the clutch mushroom pushing on the centre of them.

Close-up of a Norton motorcycle chain, sprocket, and foot peg with chrome clutch cover on a rough pavement background

With the dry build finished, I stripped the bike and sent it away for blast cleaning and painting. When it all came back it went back together very quickly as it really was a case of just bolting bits on.

The Engine

While the cycle parts were away being painted, I started work on the engine. I had no idea of the condition so it was taken apart with an open mind.

For the most part it was in very good condition. The piston was damaged so needed replacing, I had the barrel linered back to standard an fitted and ES2 piston to drop the compression ratio and make the bike more useable on the road. The valves and guides were worn so I had them replaced and the seats re-cut.

Clean

Two silver metal Norton engine crankcases on a red patterned carpet, one open to reveal inner chambers.

After stripping the engine, I had all aluminium castings vapour blasted. This really does make for a great finish but it is incredibly important to ensure they are cleaned out properly afterwards. One stray bit of grit could cause major problems later on!

Crankshaft

I assembled the crankshaft with a needle roller bearing from Ian Bennett, balanced it to suit the heavier ES2 piston and trued it up on our Alpha jig.

Following a lot of advice, I settled on a balance factor of 70% for this engine. I have since balanced several more Nortons in the 65-70% region and, although you'll never completely stop the vibration on a Norton single, I have found the results satisfactory on all of them.

Oil Pump

The oil pump was in generally good condition so I stripped, cleaned and reassembled it. New ones are available from a number of sources including Andy Molnar if required.

Cambox

Close-up of a SOHC Norton cylinder head with valve springs in a workshop, silver metal parts against blurred shelves.

The cambox was probably the worst part of the engine in terms of condition. The cams and shaft were badly worn so I bought new ones, again from Ian Bennett. The tunnel, which is an important part of keeping them oil tight was also broken up.

I've written a technical page on Norton SOHC Tunnel Repair so, again to avoid repeating myself, please take a look over there if you are interested in how I do this.

Final Assembly

Close-up of a motorcycle engine on a stand, with a timing degree wheel and a magneto static timing light against a blue backdrop.

This was carried out including tasks such as valve and ignition timing and cable making. No wiring on this one at all!

These tasks were relativity quick and easy due to the comprehensive dry build I'd already carried out.

The 'Finished' Bike

The initial restoration was finished April 2013. Just a few weeks after completing the bike, I rode it on the Sunbeam Club's Welsh week with only one mechanical issue and the usual fettling. I've since done over seven thousand miles on the bike and I've completed a range of events including the VMCC's Coventry to Brighton and International West Kent Run, the SMCC Welsh Week several more times. In 2015 Rick Parkington wrote an article on the bike for Classic Bike magazine and in 2017 and 2019 I took the bike to the Isle of Man where I did several hundred miles each time including a few laps of the mountain course.

The International has taken a bit of a back seat in the stable since my 1928 Norton CS1 came along. Although I have built it to work on the roads, the International still behaves like a race bike and although it is great fun for an evening ride, the CS1 offers a gentler ride and I tend to use that for the rallies and events now.

When you use a bike on the road, they are never really finished. Since putting this one back into use I have made several changes:

Fitted an Oil Tap with Cutout Switch. This one was made before I started Kingpin Components or had any plans to make them commercially available. The tap fitted to this bike became the first prototype!
Added a rear chain guard and a rack
Modified the rear brake pedal to make it more comfortable to use
Added the improved front brake drum mentioned further up
Re-routed the crankcase breather away from the primary chain in an effort to keep the bike slightly cleaner.
Fitted a rear view mirror