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The suspension was designed to absorb shocks and bumps
consistency under racing
conditions. Racing motorcycles
were subjected to extreme stress
during races, and engine failure was
a common issue. AJS engineers
incorporated advanced lubrication
systems and carefully tested each
engine component to ensure it
w o u l d p e r f o r m u n d e r
d e m a n d i n g c o n d i t i o n s
competitive racing.
Another challenge was the bike's
aerodynamics. The Porcupine was
designed to achieve the perfect
balance between speed and
handling, and every part of the
bike's design was focused on
achieving this goal. The frame was
crafted from lightweight materials
such as chromium-molybdenum
steel to ensure both strength and
flexibility, while the suspension
was designed to provide stability at
high speeds.
4. Technical Specifications of
the AJS Porcupine
Engine and Powertrain
The AJS Porcupine was powered
by a 500cc parallel-twin engine
that utilized a dual overhead
camshaft design. This was a
revolutionary feature for a
motorcycle of this size, as most
bikes in the 500cc class were
powered by single-cylinder
engines. The parallel-twin design
not only provided more power but
also contributed to improved
engine balance and reduced
vibration.
The engine's bore and stroke were
carefully optimized to provide a
smooth power delivery across the
rev range, making it both powerful
LHR Motorcycle Magazine Issue 12
and responsive. The engine
produced approximately 50
horsepower at peak performance,
which was competitive in the 500cc
class at the time.
The transmission was a 4-speed
gearbox, providing the rider with
the ability to manage power output
t h e effectively on the racetrack. The
o f gear ratios were chosen to provide
optimal acceleration and top speed,
depending on the race conditions.
Chassis and Suspension
The frame of the AJS Porcupine
was built using chromium-
molybdenum steel tubing, which
was both lightweight and strong.
This allowed the motorcycle to be
agile and responsive, crucial
qualities for a racing bike. The
frame design also ensured that the
engine was well-supported,
contributing to the overall stability
and handling of the bike.
The suspension was designed to
absorb shocks and bumps while
maintaining stability at high
speeds. The front and rear
suspension systems featured
telescopic forks and twin shock
absorbers, providing a smooth ride
and better control over rough
terrain.
The brakes were also designed for
high-performance riding. The AJS
Porcupine featured drum brakes
on both the front and rear wheels,
which were powerful enough to
bring the bike to a stop from high
speeds.
Design Aesthetic
T h e A J S P o r c u p i n e h a d
distinctive look that made it easily
recognizable. The spiked fins on
the cylinder heads were one of the
most notable visual features, giving
the bike its "Porcupine" moniker.
These fins were not just for
show—they helped dissipate heat
from the engine and were part of the
overall cooling system design.
The rest of the bike featured
smooth, aerodynamic lines that
were designed to reduce drag and
improve the bike's top speed. The
tank, fairing, and tail section were
21
carefully sculpted to minimize
wind resistance and improve
handling at high speeds.
Racing Success and Legacy
T h e A J S P o r c u p i n e i n
Competition
The AJS Porcupine made its racing
debut in the early 1950s, quickly
establishing itself as a formidable
competitor in the 500cc class. The
bike's advanced engineering and
impressive performance allowed it
to compete against some of the
most iconic machines of the era,
including the Norton Manx and
the Gilera 500cc.
One of the most notable successes
of the Porcupine came in the 1952
Isle of Man TT, one of the most
prestigious motorcycle races in the
world. The AJS Porcupine secured
a podium finish in the 500cc class,
further cementing its reputation as
one of the best racing machines of
its time.
Although the Porcupine did not
dominate the racing scene in the
s a m e w a y a s s o m e o f i t s
competitors, it was highly regarded
for its technological innovations
and its consistent performance on
the track.
The Legacy of the AJS Porcupine
The AJS Porcupine became a
symbol of British engineering
excellence and innovation.
Although it did not achieve the
same level of fame as some of the
other racing motorcycles of its
time, it remains one of the most
admired bikes in the history of
a motorcycle racing. Its development
marked a significant milestone in
the evolution of racing motorcycle
technology, and its influence can
still be seen in modern racing
machines.
Today, the AJS Porcupine is highly
sought after by collectors and
motorcycle enthusiasts, with
original models and restorations
commanding high prices at
a u c t i o n s . I t s l e g a c y a s a
groundbreaking machine lives on,
and it continues to inspire
engineers, designers, and riders
April 2025