Norton Model 18

Norton Model 18 Road Test

Norton Model 18This superb 1938 Model 18 trials replica might not see much of the rough stuff, but it’s a wonderful celebration of a bygone age of motorcycling. Sometimes you just know. Know that a bike’s performance is going to live up to its looks, and that’s just how I feel about this superb Norton Model 18 trials replica.

The starting drill is as simple and straightforward as the bike itself. Fuel and oil taps on, retard the ignition slightly using the lever on the left handlebar, pull in the de-compressor to get that 79mm piston moving up and down its long, 100mm stroke, and swing on the folding kick starter like you mean it. I’m rewarded first time by an, only slightly muffled, bark from the gleaming, high level pipe snaking down the right hand flank of the bike. This is clearly a well-prepared and set up machine.

Norton Model 18After a few moments to warm the bike up, I hook the sweet acting gearbox up into first and nudge the advance retard forward as I pull away, marvelling at the lightness of the clutch action. Cracking along some back lanes out in the Leicester countryside, the bike is in its element. These are the sorts of roads that time seems to have forgotten and the Model 18 is made for them.

A builders’ van swinging out of a side road brings me back to the 21st century with a jolt and gives me a rapid demonstration of the effectiveness of the 7in drum brakes. Like everything else on the bike, they’re not only well set-up, they’re also remarkably effective and I’m soon safely back in the Thirties. Winding open the throttle brings the lusty urge of the long stroke engine into play and I enjoy the sound of the exhaust bouncing back at me from the rich red Leicestershire brick of a farmyard wall. Summers are made for bikes like this.

Model 18 NortonThe gearbox is a delight. It is essential to take gear changes slowly and even precisely, I did find third gear slightly difficult to engage sometimes but I would put that down to my lack of experience on the type rather than a common problem. And as for the clutch, Even after repeated, feet-up U-turns for the camera in a narrow lane, dragging the back brake and slipping the clutch, it still steadfastly refuses to slip, drag or otherwise misbehave.

Back on more open roads, I can explore the trials replica’s performance at higher speeds. Out of respect for the age and condition of this superb machine, I’m not tempted to see if our top speed estimate of 80mph is realistic, but I’m impressed by the Model 18’s willingness to whip up to 55-60mph in no time. Who needs more than that for an hour or two on proper English country roads like these anyway?

Norton Model 18Performance is not what a bike like this is all about anyway; leave that to the Gold Stars and Vincents. What this bike does so well is to transport its rider into the past. A past where there’s less traffic, lass hassle and more time to enjoy the simple pleasures of life. Pleasures like having no particular place to go on a beautifully restored and impeccably behaved British single. And if that single looks as good as this superb Model 18 trials replica, then that’s just a bonus.

On the rough – Norton’s pre-war trials option

The Model 18 was a significant machine in Norton’s line-up, being their first overhead valve model when it was introduced in 1926. But, by 1932, the Model 18 had moved out of the vintage era into a brave new world between the wars. With dry-sump lubrication and the magneto re-sited behind the cylinder barrel, the bike looked positively modern in comparison to its predecessor. And, by 1938, a four-speed, foot-change gearbox and enclosed valve gear could be added to the list of refinements.

Norton 18 ModelBut if, as a sporting type, you wanted more than the standard Model 18, from 1935 Norton offered a Competition option for an extra five quid. Your fiver bought you a diamond-type frame, offering extra ground clearance, a stylish, high-level pipe, narrow forks and a non-QD front hub gleaned from the cammy model parts bin, a folding gear lever and slim, chrome-plated mudguards, together with trials ratios in the gearbox and knobbly tyres. That might not sound too impressive, but that would bring your bike very close in specification to the works machines of Norton trials ace Jack Williams, Ralph Dee and others. In other words, it was enough for a gentler era of trials.

Nortons OHC engines

The Norton overhead camshaft engine is probably one of the most famous motorcycle engines ever made, spanning 5 decades.

Norton Model 18The OHC engine was designed by Walter Moore during the winter of 1926/27 with its familiar dimensions of 79 x l00mm and was initially tried out by Stanley Woods in Germany in early 1927. One part of the design which never changed was the use of bevels for the camshaft drive, but early on tooth failure was a problem, a problem which was to reappear later.

The bottom half of the engine was based on the existing Model 18s but there the similarity ended. The camshaft was driven by two pairs of bevel gears and a hollow vertical shaft. The bottom gears were contained in a blister on the crank case and the top pair were encased in an aluminium cambox with the magneto placed behind the engine.

It is generally understood that Walter Moore received a better financial offer from NSU, which he decided to accept. He personally owned the design of the OHC engine, which he proceeded to make available to them and they later produced a Norton look-alike OHC engine, this in turn prompted Norton to redesign their own engine.

Arthur Carroll took over as Chief Designer, assisted by Edgar Franks and a Norton rider/development engineer, Joe Craig. Carroll, a draughtsman, together with Craig designed the now famous ‘Carroll’ engine, which first appeared at the North West 200 in the spring of 1930.

Norton Model 18This engine incorporated extensive changes from the Moore design but still retained the original bore and stroke. Then for 1932 the International appeared in both 490 and 350cc classes, and a name which was to represent world-wide sporting success was established.

During the 1930s the design changed little although coil valve springs were replaced by hairpin springs on the works bikes because of breakage (to be followed later on production models). Different materials such as magnesium and ally-bronze were used, helping to improve engine performance by reducing its overall weight and rolling resistance.

For 1935, hairpin valve springs were specified and the petrol tank was increased to 4 gallons and the oil tank to 7 pints. The gearboxes were now of a new type built by Burman and virtually copied from the Sturmey-Archer design except for a fully enclosed positive stop mechanism. This cluster was to be used virtually the same in the Commandos during the 1970s.

During 1936, the works bikes used a plunger-type rear suspension but for all others solid rear ends were the norm. From late 1937, selected riders were given the new plunger type rear suspension but without all the lightening holes.

In January 1939, Joe Craig who had been involved in the development of the OHC engines since 1929, left Norton to join BSA and Norton eventually pulled out of racing. A racing International with telescopic forks was catalogued for 1940 but never produced. The ‘over-the-counter’ Model 30 (500cc) and the Model 40 (350cc) Internationals continued with steady sales and were more popular than the CS1 and CJ versions which were dropped from production after 1939.

Specification: 1938 Norton Model 18 Trials replica

  • Engine type – ohv single
  • Bore and stroke – 79 x 100mm
  • Capacity – 490cc
  • Compression ratio – 6.5:1 (6.2:1 standard)
  • Carburettor – Amal Type 76
  • Lubrication – dry sump, gear oil pump
  • Claimed power – 21bhp @ 5000rpm (for 1946 engine fitted)
  • Transmission – four-speed
  • Ignition – Lucas magneto (magdyno)
  • Electrical system – 6 volt dynamo
  • Wheelbase – 54.5in
  • Front tyre – 3.00 x 21in
  • Rear tyre – 4.00 x 19in
  • Front brake – 7in sls drum
  • Rear brake – 7in sls drum
  • Dry weight – 360lb (est)
  • Fuel capacity – 2.75gal
  • Top speed – 80mph (est)

Norton Model 18 Gallery

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