Cycle News - Archive Issues - 1980's

~ Cl<") l-< V ,.!:j S The flow bench at Jerry Branch's southern California facility was utilized during the AMA commissioned test sessions. . V U V Q Jerry Branch and carb restrictor plate. From C.E. Axtell's business card: Old age and treachery will overcome youth and enthusiasm everytime. The AlMA and restrictors: Why? Will it work? By Joe Minton American professional dirt track racing is in a crisis. It is becoming more difficult to fill both ~he stands and the starting grids at National dirt track events. Racers, tuners and sponsors are quitting or choosing not to get into competition . h f' 1 F be l~ t ~ lfst pace. ans ~e ginnIng to stay away and It has become popular to boo the currently predominant manufacturer, Honda. A lack of participants must cover the ever increasing expenses, and - as the cost of operating a professional dirt tracker continues to go up. On the surface at lea t, the AMA's role is simply to define the rules under which racing is to take place in order to ensure that it is fair and interesting. That, of course, is a simpie minded view oC the reality of the thing. In fact, members of all parties concerned look to the AMA for an· swers and guidance. At the same time, a vocal minority stands ready to condemn any action the AMA might actually take. Ideally professional dirt track racing should be directly profitable for all concerned and, if there is to be any racing at all, must be profitable for some. The fans should leave an event pleased and feeling that they got the show they paid to see. Close racing without the winners being entirely predictable generally does that. The promoter must make a profit or he simply won't hold the race next year, that is beginning to happen. It is unlikely that there will another Houston TT as only ~bout 4500 spectators showed-up thiS year as opposed to 45,000 four or five years back. Except for a few at the top, tuners and riders have never made a profit. Knowing this, most have been satisfied if they coould meet expenses. Very few are even doing that now and tuners, sponsors and privateer riders are quitting the game in dramatic numbers. It ha sometimes been difficult to fill the starting grid this year. In 1980 there were about 3600 Expert c1as rider registered to race with the AMA; now there are 650. There will be Cewer yet in 1987. How can intake air flow restrictors help this ituation? Well, they will reduce the cost of running a Honda or Harley-Davidson engine by limit· ing its maximum rpm and increa ing its reliability. They should also c1oseupJ.he racing a bit as the power advantage of the best engines will be reduced. Roughly and simply stated: In racing practice an engine's power making limits are set either by its breathing ability or its mechanical limits.lf it runs oUI of air before it runs out of rpm, it will tend to be reliable. If it can breathe beyond its mechanical limits, it will be either unreliable or expensive to maintain. Branch monitors the testing while engineer Kevin Cameron (right) looks on. Cameron writes a monthly tech article for Cycle magazine. Both the Harley XR750 engine and the Honda, w'lich was patterned after it. can now be made to breathe beyond their mechanical rpm limits. Both are expensive to run. TheAMA madea small and informal survey among the front runners this year and learned that a good Harley can cost between $4000 and $7000 to operate for one year. A Honda runs from $7000 to $11,000. By restricting the total amount of air either engine can process, the maximum useful rpm can be brought down and they will be more reliable and cheaper to maintain. Such Iimita· tions naturally go against the grain of tuners who might see part of their hard-won power advantage taken away by a set of restrictors shoved into their engine's expensively modified intake manifolds. Opposition to a move towards restrictors is, predictably, opposed by many, perhaps most, tuners. However, the most popular and profitable racing in this country is stockcar(NA CAR) racing. The competition is intense, the outcome of any particular race is often in doubt un til the very end and lOs oC thousands of fans flock to see it all happen. If there is a single factor that has kept NASCAR racing popular and profitable it is the close control of the race cars themselves. If one brand or model gains a clear and boring advantage, something is done. Usually that something is to change the s,ize of the inlet restrictor plate that NASCAR rules require between the carburetor and the intake manifold. If a new model car or engine gets too fast, it's going to get a smaller straw to breathe through. The success of the NASCAR ap· proach has not been lost on W.A. "Bill" Boyce, manager of professional racing, and others within the AMA. They argue that restrictors can serve 11

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