In a recent post on CycleWorld.com, Maria Guidotti asked several top MotoGP riders how they'd feel about a return to 500cc two-strokes in, say, 2017. A few realists dismissed the question, but most others expressed curiosity and willingness to have a go.
In any era, there are always romantics who cherish the idea that some previous technology was the true test of "real men," which insultingly implies that today's men are somehow false. In the years leading up to 1913, racing cars were basically a chain-drive ladder-frame chassis, rolling on wood-spoke artillery wheels, with the very largest possible 4-cylinder engine shoehorned into it. Engines had displacements in the range of 16 to 20 liters (976 to 1,220 cubic inches). Those giant racers had pistons like water buckets and revved no higher than 1,300 to 1,600-rpm, making up to 200 hp. The "Beast of Turin," Fiat's S.76 record car of 1,728 cubic inches (that is a cubic foot!) developed 300 hp.
Impressive though the numbers seem, these cars were in 1912 and 1913 defeated by more sophisticated cars of only 7 liters displacement (427 cubic inches) and revving much higher thanks to double overhead cams, four valves per cylinder, and other advancements. The new Peugeots showed that cars could lap even faster if they were given a balance of qualities rather than just raw power.
So it was with the astonishing two-stroke 500s in the period leading up to 1990. Engine development seemed effortless at the time—two-stroke power gains came at a steep rate. Tires and chassis lagged behind. Kenny Roberts' 1980 aluminum-frame 0W53 (main photo) weaved so violently at Assen that its front tire went flat at 150 mph. In 1982, riders were coming to the line with tires shiny from mold release—not even scuffed, in hope of eking out another good lap or too before they turned to grease. Marco Lucchinelli's winning strategy was to hang back for seven laps or so to let the leaders "burn down" their tires. Then, with his own tires largely undamaged, he would advance to pass them all. Violent two-stroke powerbands made mincemeat of tires.
The coming of radial-ply construction and intense tire competition produced tires with phenomenal grip, but with essentially no warning of when all of that grip ended. That, combined with the two-stroke's sudden, peaky power, led to a growing number of corner-exit highside crashes. Riders, striving to maximize acceleration, drove their tires into a cycle of slip-and-grip that was spectacular but too often ended in a violent highside. The FIM responded with an increased weight limit and threatened to require intake restrictors.
The first year of electronic rider aids was 1990. Torque was limited in lower gears. The violent highsides receded. As the 1990s unrolled, a variety of engine-smoothing and traction-enhancing technologies were adopted. In 1997, I marveled as Mick Doohan went out to practice at the German GP, his NSR500 Honda pulling from low revs in a smooth grrr.
Spectacular though the two-strokes were, and remarkable as they were in their ability to match or exceed the best four-stroke combustion pressures, these were machines that riders were lucky to walk away from.
Not only that, their lap times had stagnated. Power from the 500cc engines had zoomed to very near 200 horsepower, but then it had to be moderated for human rideability. The firm Swissauto produced a 500 two-stroke that did make 200 hp, but that raw power—like that of the 16-liter giant racers of 1910—rendered it unable to lap competitively. Sadly, the two-strokes had become muscle-bound.
The goal of design in racing is to win races, not to produce accidents and injuries. When 990cc four-strokes in 2002 produced a clearly superior match of engine torque output to what tire traction could handle, lap records began to fall again, and have been doing so ever since. I loved my 20 years with two-strokes, but I saw their inherent problems up close. I would love to see two-stroke GP bikes built with today's technologies, but understand why that is extremely unlikely.
