1956 AJS 18CS: Street-Made Dirt Bike

During the war years, American GIs fighting overseas had the opportunity to become acquainted with the light and agile English machinery, and they were impressed: Where our bikes were lumbering twins, theirs were mostly slimmed-down singles. Soon after our boys came marching home, civilian versions of British military bikes went on sale at a discount in America. England, desperate to pay off war debts, had devalued the pound and pushed manufacturers to export, and export they did.

Dirt bike for the street

Although the 1956 AJS 18CS was basically an offroad competition machine (what would now be known as a motocross bike) in England, the used 18CS that John bought in 1958 on his return home from military duty was set up as a road bike, as apparently were all 18CSs imported to the U.S. He found it at Ghost Motorcycles, the AJS/Matchless dealer in Port Washington, N.Y., one of the largest bike dealers on the East Coast. “I was fresh out of the Marine Corps,” John remembers. “I commuted on it and I loved it. It was a fun bike.”

Although the AJS motorcycles imported to the U.S. apparently had lights already bolted on (in England, lights were an extra charge item), a plug built into the bottom of the headlight shell made it easy to detach the headlight for a day of scrambles or flat tracking. Cooper Motors, the California AJS/Matchless importer, advertised the AJS 18CS as “a real sports motorcycle, ready to go in the dirt or on the road” and capable of “over 100mph,” which was more than a little optimistic.

For the 1956 model year, the AJS 18CS had a redesigned, almost square (equal bore and stroke dimensions) 497cc engine (earlier bikes had a smaller bore than stroke, or under-square design). The redesign featured a more robust crankpin running on long caged roller bearings. The drive side mainshaft was supported by ball bearings, the timing side featured a bronze bushing, and a third roller bearing close to the flywheel provided additional support. This third bearing was a feature of all AJS/Matchless bikes.

The cylinder barrel was made of aluminum alloy with a bonded cast iron liner and built-in pushrod tunnels. The aluminum head used on earlier models continued with no changes. Compression ratio was 8.7:1, a major advance from the early Fifties when ratios were in the range of 7:1. (Postwar Brit bikes ran low compression in order to cope with the horrible English gasoline of the time.) Gas mix was provided by an Amal Monobloc carburetor, spark by a Lucas magneto and light by a Lucas generator.

The CS frame was new for 1956, with a shorter wheelbase. It was basically the same as the one used on the road bikes, albeit with some additional bracing to keep it from suffering under the rigors of trail use. Tradition was maintained by using the famous “Jam Pot” rear shocks (so named because of their fat upper portion) first introduced in 1951. A further selling point was the strong full-width hubs used front and rear. The bike came with Dunlop trials tires, and John remembers that his AJS would go anywhere and do anything he wanted it to — except go fast. “I loved it, but it wasn’t fast enough. I traded it in for a Gold Star,” he says.

AJS number two

In the 1970s, by this time married and with family, John suffered an offroad accident scary enough to push him to trade in his motorcycle habit for sailboat racing. But as the years went on, sailboat racing started to become tiresome. Besides the expense, John says that finding competent crew members was always a struggle.

In 1995, John was diagnosed with kidney cancer. Looking for a distraction, he happened to read how old bikes were becoming popular, and thought he might try his hand at restoring one. Shortly afterward, he discovered one of his neighbors had two Triumphs, and better yet, he knew of a BSA Lightning for sale.

John bought the BSA, and recovered as he restored the motorcycle. Healthy again, he decided he liked working on old British iron and looked for another bike to restore. He was poking through the local paper when he saw an ad for a 500cc AJS single. “I called and asked what the engine numbers were,” John recalls. “The seller said 18CS. I said I would be over there in five minutes.” The bike proved to be an older restoration in need of TLC, but it was just like his first AJS. “It was running — but barely — and the frame was bent, but the CS is really neat and hard to find,” John adds. Naturally, he bought it and went to work.

The first stop was to a frame man to straighten the bent frame. The wheels were treated to new bearings and new tires. John was able to find a Dunlop rear tire, but the closest front tire available in a 21-inch size was a Barum from the Czech Republic.

The wiring harness was the usual snarl, prompting John to throw it out and replace it with a new one. Most of the running problems were due to the bike’s Amal Monobloc carburetor, which had worn out completely, a common problem on old Amals as they used a body and slide made of the same soft alloy, resulting in rapid wear to both pieces. John’s solution was simply to buy a new Monobloc.

The previous restorer had a sign painter craft the AJS logo on the tank. Whoever he was knew what he was doing, because it’s quite fantastic. John wisely chose to preserve that part of the old resto, so he had paint man Joe Cook carefully clean the old paint and put a new layer of clear coat over the entire tank to preserve it. He also repainted the oil tank and toolbox. The results speak for themselves.

Although he now has a variety of motorcycles in his garage — including a new BMW — John chooses the AJS for short breakfast runs and longer club rides on back roads. “Some friends and I were going to a meet, so we trailered our bikes up the freeway and then unloaded and explored all the back roads leading to the meet. I took the AJS, because it’s really good for that kind of smell-the-roses riding,” John says. Given its intended role as a trials bike, he’s pleased with its road manners, although he thinks it would be a great motocrosser. “It has lots of torque, a wide power band and it’s very forgiving. It isn’t very fast, and it brakes like an old British motorcycle. I downshift a lot and use engine braking. The Burman 4-speed box is smooth shifting, and it’s comfy to ride at a moderate pace,” John says. “I ride it accordingly.” Sounds like a recipe for a perfect Sunday. MC