AJS produced a 368cc motocross bike, the Stormer Y5, from 1969 to 1974. The Stormer Y5 was a two-stroke dirt bike that was modeled off of the Villiers Starmaker. It was also called the AJS Stormer 370.
Engine:
Bore and Stroke: 83x68mm
Capacity: 368cc
Compression Ratio: 11:1
Port Timings Exhaust: 180 degrees, Transfer: 130 degrees, Inlet: 170 degrees.
Ignition Timing At Piston: 2.5mm at Crankshaft: 20 – 22 degrees.
Contact Breaker Gap: .38mm
Spark Plug NGK B8ES – Champion N3 Plug Gap: .635mm
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The Cagiva WMX125 was first released as a prototype in 1978, and became the world’s first production motocross bike that was liquid-cooled when it entered production in April of 1979. The WMX125 had a single-cylinder, 124.6cc engine. The engine used both air and water to cool itself. It had a 34mm magnesium Dell’Orto carburetor and magnesium engine covers. Reed-valve induction and a six-speed gearbox were other features on the first WMX125. It also had an aluminum cylinder with a nikisel bore, making it stronger than most of the competition’s chrome system. This 125 lead its class in power output, with about 30hp. Great power for a 125cc, especially for the time period.
The frame of the WMX125 was constructed using chrome-moly tubing, and the suspension first consisted of 35mm Marzocchi leading axle forks with magnesium sliders, and were soon upgraded to 38mm. A pair of Corte Cosso gas shock absorbers were in place in the rear of the bike, an aluminum radiator was used to save on weight, and a very strong American-made swing arm.
The bike was tweaked a bit in the early 80s. Cagiva’s 1983 WMX125 had a mono shock that they called the “Soft Damp System”. Other changes lead to a higher power output of about 35hp. The carburetor was increased to 36mm, too, and the bike was quickly becoming a contender for the world motocross championship. Cagiva actually won the 125cc world championship in 1985, and released a “World Champion Replica” production bike in 1986. The only thing that differed from the actual championship-winning bike was the bore-and-stroke dimensions. Soon after their win, however, Cagiva purchased Husqvarna and the Cagiva WMX125 was no more.
Danny LaPorte is a motocross racer that had a big hand in further popularizing the sport in America. LaPorte was born in Southern California in 1957, to a father that was an off-road motorcycle racer himself. LaPorte began racing local motocross races at age 11, and soon realized his talent. He began riding at a professional level in Southern California when he was 16. He was so much better than the competition, however, that he became bored by the time he was 17.
Around this same time, LaPorte made a trip to Snake River Canyon, Idaho to watch Evel Knievel’s tragic rocket cycle jump. “There was a motocross race held in conjunction with the jump and it had a $100,000 purse. I watched Marty Smith win the 125 race and I couldn’t believe it,” LaPorte said. He had previously raced against Smith multiple times, and usually beat him. Watching Smith win with such ease, and win $100,000 was the inspiration that he needed to get back in the sport. He did so well the next season that Suzuki called him, asking him to be a part of their factory team for 1976. LaPorte accepted, and made his debut in the AMA National Motocross Series on a 125.
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