The Sept. issue MotoCross Action pg.32 has a good article on this issue. The writer makes compelling arguments for reasons why 2smokes will be phased out. Its a good read. Here's the article in its entirety: "Under current AMA rules, it is legal to race a 550cc four-stroke in the 250 class. No matter how conflicted you are about the four-stroke formula, it's time to suck it up and live with it. Four-strokes are here to stay- in fact in the not-too-distant future, four-strokes could be all that the Japanese manufacturers are producing. WILL TWO-STROKE BIKES BE BANNED? Yes and no. Most manufacturers are working under a five-year plan to phase two-strokes out of their line-ups. However, even if the Environmental Protection Agency cracks down on two-stroke off -road machines, it will not restrict two-strokes for closed-course racing. Two-strokes will not be banned, but they will be limited to race courses only- and while the smog police may not crack down on you for riding in your back yard they will make the manufacturers' lives miserable. If the scales of two-stroke bikes are diminished in significant numbers by a closed-course-only restriction, the manufacturers will not have the economy of scale necessary to continue producing them. Under the five-year plan, the manufacturers are planning on replacing two-strokes with four-strokes. It's inevitable (just as it was with street bikes 15 years ago). WON'T THE FACTORIES KEEP RACING TWO-STROKES? No. Once the factories make the move to phase out two-stroke production(estimated to happen in 2008), they will be geared up to race and sell four-strokes. Time Ferry, Doug Henry and Ryan Hughes are stalking horses for what will be a wholesale switch to four-stroke race teams in the next half a decade. There is no reason for the factories to race bikes that they don't sell. Plus, once they commit to 250cc and 450cc four-strokes, the horsepower numbers are going to skyrocket while the dry weight comes down. In short order the new breed of four-strokes will dominate. WHAT WILL HAPPEN TO THE AMA CLASS STRUCTURE? It's history! The 250 class will become a 450 class (and every manufacturer will build bikes right to the 450cc max) and the 125 class will become the 250 class. Even if the AMA continues to call the classes the 125 and 250 National Championships, there won't be any bikes of those displacements in the classes. The writing is on the wall for the 125 class already. This year's AMA 125 National Championship has seen an influx of privateers mounted on Yamaha YZ250Fs- and they are doing well. Once Honda releases its anticipated CRF250, no one will be on a two-stroke except factory-sponsored two-stroke riders. You don't have to have a crystal ball to predict that next year's 125Nationals will have twice as many four-strokes (and so-on through the years). WHY WILL THE FOUR-STROKES TAKE OVER SO QUICKLY? Thanks to years of road-race technology, the factories have the where-withal to procuce phenomenal amounts of horsepower out of a 250cc four-stroke cylinder. As development dollars are thrown at the next generation of four-strokes, they will only get faster, lighter and torquier. At the same time, development dollars will be withdrawn from two-stroke technology- meaning two-strokes will stagnate at their current horsepower ratings. Since Yamaha is the only manufacturer to produce a 125 two-stroke and a 250 four-stroke, they will be the first to see market share stolen by their own bike. Sooner or later, YZ250F sales will harm YZ125 sales. When that happens, Yamaha will drop the YZ125 and put all its eggs in the four-stroke basket. IS THE 125 CLASS DEAD? Yes. Under the current rule structure the 125 class is doomed (although we are in for five thrilling years of two-stroke versus four-stroke dueling). How will you know when the days of two-strokes are numbered? When a factory team puts its number-one rider on a thumper. The day that happens is the day the two-stroke aficionados can start chiseling a tomb-stone. Paradoxically, the mini class is also perched on the edge of a major change. Honda and Yamaha currently make 50cc, 70cc,90cc, 100cc, and 125cc four-strokes. They don't plan on continuing to produce 85cc two-strokes forever. The AMA must develop a displacement formula for minicycle-legal four-strokes. And no matter what formula they choose, there will be howls of protest. WHAT WILL THE AMA DO TO SAVE THE DAY? Hopefully they will seek outside help because their track record for making sensible and pro-active decisions is pitiful. There is lots of pressure for the AMA to rewrite the 250cc four-stroke formula to essentially neuter the YZ250F. This would be a big mistake. First, because Yamaha would have them in court quicker than you can say "shyster". The four-stroke formula was written with the intent of encouraging four-stroke development. To change the rules now, after Yamaha has spent mult-millions of dollars responding, would be interpreted as restraint of trade. As a starting poing, the AMA needs to sit down with something better than a foggy crystal ball and get a clear view of the future. They need to delve deeper into the factories' five-year plans, analyze where the machinery is headed and try to develop formulas that will not only work today, or five years from now, but far into the future." end All this means the 4stroke battle will really heat up. Very cool.