Editor’s Note: Indian Motorcycle has responded to a trio of rule changes in the Twins class set forth by American Flat Track. One of which Indian Motorcycle feels unfairly singles out the Scout FTR750: increasing the allowable throttle body diameter from 38mm to 40mm for production-based engines. The Scout FTR750 is not a street-legal production motorcycle, and Indian feels that it will not be able to compete on a level playing field with its smaller 38mm bodies, citing a 20- to 22-percent increase in airflow in a 40mm throttle body over a 38mm unit. I asked the guru for all things technical at Cycle World, Kevin Cameron, for his take on this rule change.
For many years dirt track racing in the US was dominated by the made-for-racing aluminum Harley-Davidson XR750. The idea of a production-based dirt-tracker didn't really become important until veteran tuner Bill Werner—and others—made the Kawasaki Ninja 650 competitive (legally bored and stroked to 750). Just before Indian fielded its made-for-racing FTR750 V-twin two years ago, a pit walk revealed that the Ninjas were the most numerous bikes in the field.
Yet the very expression “production-based” has no precise meaning. Production parts in that Ninja parallel twin include the crankcase and cylinder head, but the crankshaft, connecting rods, pistons, and certain other critical items are racing parts manufactured my specialist firms in small numbers. That makes them expensive. In the case of Harley-Davidson’s “G-bike,” based on the single-overhead-cam “Street 750” production bike, Harley’s racing subcontractor Vance & Hines has had to make racing-only double-overhead-cam cylinder heads. If Harley decides to make these bikes available to private teams (it has not yet done so), will the DOHC heads be considered “production-based”? If so, could those engines legally be increased to 900cc displacement? As these examples show, there is no hard line between racing-only and production-based. Formula 1 teams employ lawyers to work out precisely what is possible under particular rules wordings.
Indian’s success in AFT racing has been overwhelming, such that AFT feels it necessary to make some adjustment to improve the competitiveness of production-based bikes. That takes the form of 2 extra millimeters of minimum intake-tract diameter—a change from the 38mm allowed on the 750cc race-only engines, to 40mm for production-based engines up to 900cc.
Ninja-based engines are already very strong on the mile, and the increased intake diameter will add to that strength.
Indian Product Director Gary Gray acknowledged that while winning races is the goal of its racing, boring single-brand dominance could reduce the power of AFT to get spectators excited about motorcycles. While he understands AFT’s goal in making the 40mm change, he says, “It’s what happens in the last 50 feet before the finish line that concerns us.”
Handling and just the right kind of power delivery launch a bike off the turns, but, “Air is what they need for the finish.” Gray believes the change to 40mm intakes will put Indian at a competitive disadvantage.
The engineer’s way of looking at this would be to observe that equal intake areas should result in equal horsepower—regardless of engine displacement.
In the past, AFT has allowed 44mm intakes on very large production-based engines as an incentive to bring more brands to the show. None of them has been successful—private teams have been unable to combine competitive handling with the right kind of power delivery, and other manufacturers have not stepped up as Indian has with a fully engineered package. Bill Werner explained that peak horsepower cannot make up for what less developed bikes lose in not hooking up and getting the drive off the turns.
The new rule will limit production-based engines to 900cc. This extra displacement is allowed to compensate for these bikes’ higher weight and non-racing design.
Werner commented that even if teams running production-based Ninjas or Yamaha twins wanted to increase displacement to 900cc, the design of those engines would limit the increase to 20cc or so—not significant.
There is more. AFT has announced a production class to run at 10 or 12 events next year. This provides an intermediate step for riders moving up from Singles to Twins and, as Werner comments, “should be well-received.”
Is this production class just another race in the show? Or is it the seed of what the AFT series could become if interest shifts away from the “three-horse race” of Indian versus the Ninjas and Harley? In the early 1950s, Alfa Romeo dominated F1, so promoters switched their focus to the more numerous entries in Formula 2.
That leads to yet another question. It’s expensive to build a competitive Ninja and requires special skills. In a world where those skills are increasingly rare, where would all those engine builders come from? That question was answered in Dorna’s Moto2 class by adoption of a single spec engine—identical for everyone. Seen that way, the Indian is a valuable gift to American racing. Instead of struggling to make a homemade or artisan chassis hook up while engineering traction-building flat torque into a Ducati, KTM, or Triumph streetbike engine, a team might put that effort and expense into a fully engineered racebike that works. This is a choice.
Americans love to root for the underdog, the do-it-yourselfer, the little guy. Racing itself will determine which way is the future.