Ariel Twin-Cylinder Motorcycles
Ariel Twin-Cylinder Motorcycles Background & History
Ariel Twin-Cylinder Motorcycles were meant to follow Triumph’s successful foray into vertical twins, starting with the seminal 500cc 1938 Triumph 5T Speed Twin, the world’s first ‘modern’ vertical twin (aka: parallel twin). Triumph too the world (the motorcycle world, that is) by surprise and by storm with the bike. Instantly, the whole landscape changed in a market ruled by big single-cylinder bikes. The rest of the British motorcycle industry (those who could afford it, anyway) scrambled to develop their own vertical twins. Alas World War 2 happened and froze everything for 5 years, but when it ended motorcycles started pouring out of England again, into the waiting hands of the anxious masses. BSA was first in 1946 with their own vertical twin, the 500cc BSA A7. Ariel was next in 1948 with their own twin-cylinder motorcycles, the 500cc KG (mildly tuned) and KH (high-performance version). Norton, Matchless/AJS and Royal Enfield all hit the market with their own vertical twins in 1949.
Ariel twin-cylinder motorcycles all started with this model in 1948, the 500cc KH. This one is a 1954 Ariel KH.
Ariel Twin-Cylinder Motorcycle Design
Designed by genius motorcycle designer Val Page, Ariel’s 500cc twin-cylinder motorcycles were produced from 1948 through the 1957 model year. Offered in two versions, standard (KG) and hot rod (KH), much like Triumph had done with the 500 Speed Twin (standard) and the T100 Tiger (the hot rod). Ariel’s new line of twin-cylinder motorcycles showed great promise, and Ariel along with parent company BSA were optimistic about its future. However, the market was stacked high with worthy competition, a market totally dominated by Triumph and to a lesser extend BSA. But, the new Ariel KH was a handsome machine with it’s red-and and it was fast, capable of 90 mph, easily keeping pace with a Triumph Speed Twin or a BSA A7. And the Ariel was even priced lower than most of their rivals. What they lacked was street cred and racing pedigree. They had a well-earned reputation for quality and dependability, which wasn’t enough in a market flooded with hot, sexy bikes. As the result, the sales never really came and the whole line of Ariel twin-cylinder motorcycles failed in the marketplace. Today you rarely see them at shows or auctions simply because few were sold and so few were built.
This 1954 Ariel KH500 shows how Ariel's 500 vertical twin was a unique piece, developed completely in-house at Ariel. The later 650s were rebadged BSA A7s.
Ariel Twin-Cylinder Motorcycle Models
Upon initial launch, all early Ariel twin-cylinder motorcycles used rigid frames from Ariel’s single-cylinder fleet, however Anstey-link plunger rear suspension was available as an option. Swing arm rear suspension hit Ariel twin-cylinder motorcycles in 1954. Telescopic front forks were parts bin-sourced from parent company BSA’s vast inventory. Also in 1954 the alloy cylinder head became standard. In 1956 the ancient steel single-sided hubs were replaced by modern aluminum full-width hubs. Over the next few years, these Ariel Twin-Cylinder Motorcycles were steadily improved and ‘hopped-up’. In 1954, the KH got a new, higher-performance variant, the KHA which had an alloy cylinder head, instead of the old cast iron head. Bear in mind that the competition, mostly from Triumph, but now from the others as well, was fever-pitched and Ariel, along with everyone else, was constantly looking for an edge to exploit for their own vertical twins’ success. Once the rest of the industry caught up with Triumph’s 500cc vertical twin in 1949, Triumph did it again and punched out the 500 to make the industry’s first 650 twin with the 1950 Triumph 6T Thunderbird. Again, the rest of the market rushed to catch up. Ariel fielded it’s first 650, the Model FH in 1954. But this time, instead of following Triumph’s example and simply boring and stroking out their existing 500 to get to 650cc, Ariel, now owned by BSA, simply used BSA's 650cc A10 engine and dolled it up with unique ‘Ariel’ side covers. Badge engineering had arrived at Ariel.
The engine in the 500cc Ariel KH was unique to Ariel, not a BSA piece.
Ariel Cyclone
The ultimate iteration of Ariel twin-cylinder motorcycles was the 650cc Ariel Cyclone which was in production from 1958 through the Again, it was based on BSA’s 650cc A10 Golden Flash but with some mechanical differences that were exclusive to the Ariel. It wasn’t just a cosmetic makeover. Among other things, Ariel added a hotter cam, a better crankshaft with bigger bearings and a higher 8.5:1 compression ratio to the BSA A10 to create the Cyclone. The Ariel Cyclone was advertised as “40 cubic inches and 40 horsepower”, which put it on par with the fastest bikes from Triumph, BSA and Norton.
Ariel's 650cc entry into the vertical twin race was the model FH. But the hottest vertical twin that Ariel made was the 650cc Ariel Cyclone, based almost entirely on the 650cc BSA A10 Golden Flash.
The End is Near
Alas, none of this helped. Only 300 Ariel Cyclones were sold (Buddy Holly owned one). BSA pulled the plug on the 500cc Ariel KH line in 1957 and the 650cc BSA A7-based FH in 1959. Ariel struggled on for a little while longer, trying to sell their ugly line of tiny, budget-minded bikes, the Ariel Leader and Arrow. BSA finally ran out of patience in 1967 and pulled the plug.
It's easy to spot the obvious similarities to the BSA A10, because it is one, other than the Ariel-unique timing cover which reads "Six Twin Fifty", whatever the hell that means.
Ariel Motorcycle Books
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Ariel Twin-Cylinder Motorcycles
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