Comparing the BSA A7 and Norton Model 7

By Robert Smith
Published on May 29, 2013
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BSA and Norton responded to the twin format with their own take, but each adopted design approaches that were different from the other — and from Triumph.
BSA and Norton responded to the twin format with their own take, but each adopted design approaches that were different from the other — and from Triumph.
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The A7 powertrain went into a conventional lug-and-braze mild steel tube frame, with a rigid rear and BSA’s own telescopic fork at the front, though the frame did make somewhat ingenious use of the seat tube.
The A7 powertrain went into a conventional lug-and-braze mild steel tube frame, with a rigid rear and BSA’s own telescopic fork at the front, though the frame did make somewhat ingenious use of the seat tube.
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The Norton makes 29 horsepower.
The Norton makes 29 horsepower.
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The BSA’s twin makes 26 horsepower.
The BSA’s twin makes 26 horsepower.
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The Norton Model 7 used a built-up crankshaft, with the inside webs bolted together through an integral flywheel.
The Norton Model 7 used a built-up crankshaft, with the inside webs bolted together through an integral flywheel.
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The BSA A7 is functional and spare, almost stark — especially its rigid frame — though the gas tank is lavishly chrome-plated, a BSA hallmark.
The BSA A7 is functional and spare, almost stark — especially its rigid frame — though the gas tank is lavishly chrome-plated, a BSA hallmark.
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Presumably to avoid infringing BSA patents, Norton chief designer Bert Hopwood positioned the single camshaft at the front of the engine instead of the rear, driven by chain from a half-time gear.
Presumably to avoid infringing BSA patents, Norton chief designer Bert Hopwood positioned the single camshaft at the front of the engine instead of the rear, driven by chain from a half-time gear.
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The BSA A7 and the Norton Model 7 may look quite alike, but the Norton feels more precise going down the road.
The BSA A7 and the Norton Model 7 may look quite alike, but the Norton feels more precise going down the road.
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BSA owner Dave Higgs (left) rides with Norton owner Jim Bush.
BSA owner Dave Higgs (left) rides with Norton owner Jim Bush.

What if Harley-Davidson announced they were going to build an inline 4-cylinder motorcycle? Or Ducati said they would build a triple? It just wouldn’t be right, would it?

Now imagine the furor surrounding Norton’s 1949 announcement
that they would launch a twin-cylinder bike. From the time they started
building their own engines in 1912, Norton had produced only singles, including
sidevalve and overhead valve units and the famous overhead cam Manx. For Norton
to forsake its heritage was something close to sacrilege — “Pa” Norton would be

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