Sunday, January 29, 2012

1958 Ariel Square Four MK II and Ariel Motorcycle History

"You will never find, see, or ride, a better example of the famous Square Four Ariel. It was restored to absolute show condition by a very experienced Texas restoration expert and collector. The engine/transmission was built by Keith Martin of Big D Cycle fame. It has been the center piece of a private museum for the last several years. The bike starts, runs, and rides just as it looks. The torque of the four cylinder engine is amazing. It starts very easily and after a few minutes of warm up runs out better than it did in '58. This is obviously not an everyday bike, but it can, and should, be ridden regularly. There is no problem keeping up with modern traffic, but you must remember the bike has brakes from the fifties era.  The bike will be delivered to the new owner with a fresh service, fully charged battery, and ready to show or ride. This is isn't a distress sale, and is not cheap, the best never is. 

I've been collecting vintage motorcycles for over 30 years and I've never seen a Square Four even close to the condition of this bike. You  can be assured you won't see another like this at a show or Sunday ride. If you are interested in seeing the collection's website visit  PLEASE DO NOT email me about other bikes that might be for sale. If anything is for sale it will be on ebay at a future time.

I'm selling this bike only because I don't ride it often enough. I'm selling a few of my bikes that are not ridden often enough, or that I have more than one example. The bike has a clear and open Texas title. It has not been registered in Georgia since I just never used it that much."

1958 Ariel Square Four MK II
1958 Ariel Square Four MK II
1958 Ariel Square Four MK II
1958 Ariel Square Four MK II
1958 Ariel Square Four MK II

More information about Ariel Motorcycles from

The 1957 Ariel Mk II motorcycle was developed by one of the British motorcycle industry's more adventurous manufacturers. Begun in 1902, Ariel produced an array of singles and twins of both two- and four-stroke design, but it is this unusual four-cylinder model that is perhaps best remembered.

During the 1920s, Ariel's Edward Turner had dreams of changing the world of motorcycling. For many years, twin-cylinder engines were the powerplant of choice, but Turner had grander ideas.

Envisioning a four-cylinder engine that would fit neatly into a typical frame, he devised the unusual "square four" design. It used two crankshafts geared together and four cylinders arranged in a square pattern, with a pair of pistons tied to each crankshaft.

Displacing 500 ccs, the first Ariel Square Four appeared in 1931, venting its exhaust through only two pipes. The four was enlarged to 600 ccs in 1932, and then to 1000 ccs in 1936.

In 1953, the Ariel 4G Mk II version appeared, carrying a four-pipe exhaust system and an alloy block in place of the previous iron version.

Some other changes were evident by this time as well. The tank-mounted instrument panel was eliminated and the gauges were now mounted atop the wide headlight nacelle.

A new plunger rear suspension provided a softer ride but needed fresh lubrication every 250 miles. The girder front fork had been converted to telescopic in 1946 and went largely untouched.

Turner left Ariel to join Triumph in the mid 1930s, where his talents in developing the Speed Twin helped revive the ailing concern.

Ariel's success with the Square Four continued through the 1950s, after which the company concentrated on medium-displacement two-strokes that were a cross between a scooter and a motorcycle.

The engine of the 1957 Ariel 4G Mk II motorcycle used the "square four" design, which consisted of two crankshafts geared together and four cylinders arranged in a square pattern, with a pair of pistons tied to each crankshaft.

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