1934 Norton International
When Walter Moore left Norton for NSU in 1929, Arthur Carroll was tasked with re-designing to OHC (Overhead Camshaft) models. The 500cc Model 30 and the 350cc Model 40 Internationals where first listed for sale in 1932. They where quickly adopted for competition use and proved incredibly successful throughout the 1930s.
The Internationals sold to the public where usually just behind the works racers in terms of development and engine tune and came with a list of options for items such as cams, gearbox ratios and lights. Although fundamentally unchanged the Internationals where developed throughout the 1930s with improvements such as alloy barrels and heads and, later, plunger rear suspension. By 1939 the Inter had been developed as much as it was every going to be.
Post war the Manx took over as the number one choice for competition and the Inter, reintroduced in 1947, went back to a cast iron barrel and head and was given the standard garden gate frame and roadholder forks. By the late 40's the Manx had well and truly taken over as the serious racers choice, as did the BSA goldstar for the clubman racer. 1953 saw the adoption of the featherbed frame and the restoration of the alloy barrel and head, however this only lasted a couple of years as the International was dropped from the Norton catalogue in 1955.
Production of the Manxs continued to 1963 and by then they resembled the early International very little with short stroke double OHC engines, featherbed frames and AMC gearboxes.
My International
Purchased on eBay in 2011 this International has a 1934 rigid frame and 1936 alloy engine. Shown in this picture 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 all the missing parts where sourced, and what couldn't be sourced was made or adapted from similar parts.
The Dry Build
Possibly the most important part of a project like this is the dry build. So many parts need to be made, modified and fitted 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 paint work on 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 main shaft twist the gearbox
in the frame and snap the lugs off of the top. Fortunately this gearbox had not yet suffered this, however it was worn so something had to be done to prevent future damage.
Both frame and the gearbox where bored out and top hat bushes where fitted. This, combined with new fixing bolts ensures a
tight fit and no room for movement.
It is vitally important when working on the top mount to ensure the gearbox is a tight fit over the frame. If it isn't the lugs can be snapped off when the gearbox is tightened up as they do not bend in to take up any slack.
If a gearbox has already been broken it is possible to weld the casing and then carry out this type of work to prevent it happening
again. If you simply weld the lugs back on and don't get rid of the wear everywhere else it wont be long before the box breaks again.
Mudguard Brackets and Stays
Mudguards where bought from Paul Norman at Racing Norton. The quality was superb and we then made brackets and stays as shown in these pictures.
A swaging tool was made to be used with a fly press for squashing the ends of the tube. Much neater than simply squashing it a vice, stronger too!
The top mudguard bracket was made from a flat sheet of steel. Cut, filed and formed manually. No point making jigs and tools for a one off like this.
Tank Brackets
These where not available at the time some one had to be made. This is just one example of the huge range of brackets, bolts, fixings and so on that where made in house
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.
Fork Repairs
The forks and spindles where badly worn. The forks where bored out and bronze bushed fitted. We show you how to do this in one of our technical pages. We also made a set of the spindles from EN16. We now have these and other fork parts for sale in our shop.
Wheels and Brakes
The hubs where missing all together but fortunately all 1930's Nortons where fitted with the same ones so they are fairly common. We did however have to make wheel spindles and modify the front brake plate to work on the right hand side of the bike as this was unique to Internationals. Everything else had them on the left at this time.
There are plans to make an aluminium brake plate in an effort to further improve the front brake as and when time allows.
Once the bike was on the road the front brake turned out to be woeful. A new brake drum was made from a solid piece of cast iron complete this stiffening ribs around the outside. This considerably improved the brake.
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 the bike was badly worn so an ES2 one was bought, turned down to the correct thickness and the cutaways put in using the indexing head on our Bridgeport milling machine.
The basket was then copper plated, the pressure plate chrome plated and the clutch assembled using Surflex plates. The clutch is incredibly light and works as well as on any bike I've ever ridden.
New adjusting screws where made in stainless and a plate was put behind the pressure plate to spread the load when operating the clutch as the pressed plates in these tend to distort with just the clutch mushroom pushing on them.
With the dry build finished the bike was stripped and sent 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. Some things where modified after riding the bike, as well as the front brake drum mentioned above, the crank case breather was routed away from the primary chain as otherwise the back end of the bike was permanently mothered in oil and the rear brake pedal was bent to sit in a more comfortable position for use.
The Engine
While the cycle parts where all away being painted, work on the engine was carried out. We 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, we had the barrel linered back to standard and fitted and ES2 piston to drop the compression ratio and make the bike more useable on the road. The valves and guides where worn so where replaced and the seats re-cut.
Clean
After stripping all aluminium casting where 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
The crankshaft was assembled with a needle roller bearing from Ian Bennett, balanced to suit the heavier ES2 piston and trued up on our Alpha jig.
Oil Pump
The oil pump was in generally good condition so was stripped cleaned and resembled. New ones are available from a number of sources including Andy Molnar if required.
Cambox
The cambox was probably the worst part of the engine in terms of condition. The cams and shaft where badly worn so new ones where bought, again from Ian Bennett. The tunnel, which is an important part of keeping them oil tight was also broken up. We have a Technical Page on SOHC Oil Leaks so more information on this work is there.
Final Assembly
This was carried out including task such as valve and ignition timing and cable making. No wiring on this one at all!
These tasks where relativity quick and easy due to the comprehensive dry build carried out.
The Finished Bike
The restoration was finished April 2013. Just a few weeks after completing the bike completed the Sunbeam Club's Welsh week with only one mechanical issue and the usual fettling. As off 2020 it has over seven thousand miles on the clock and has completed a range of events including the VMCC's Coventry to Brighton and International West Kent Run, the SMCC Welsh week several more times and in 2017 and 2019 I took the bike to the Isle of Man and did several hundred miles each time including a few laps of the mountain course.
Since the bike was ‘finished’ we added a rear chain guard and a rack, modified the rear brake pedal and added improved front brake as mentioned further up. There are further plans to continue improving the bike but in the meantime it has proved to be a great bike, if a little impractical in traffic!
In April 2015 Rick Parkington did an article on the bike in Classic Bike Magazine.
