Here's from MXperts in the new MXA,... "Why didn't four-strokes replace two-strokes years ago?It is so obvious that four-strokes are better." ...Answer... "So much for your deductive powers,Sherlock.In truth,two-strokes are the ultimate motocross racing engine.A two-stroke engine weighs less,has fewer moving parts,has a significantly reduced maintenance cost,revs quicker,is cheaper to manufacture and produces more horsepower per liter than a four-stroke.If two-strokes had been invented yesterday,we would be hailing their arrival as a watershed moment in engine technology.So ,why are four-strokes dominating now?It is a combination of pending EPA legislation (with which the manufacurers must comply),me-tooism on the part of consumers,and the fact that four-strokes are allowed,under AMA rules,considerably larger displacement.Without the extra displacement,no one would be racing a four-stroke today."...I thought the "me-tooism" was pretty funny,to bad so many people just jump on the four-stroke wagon because of a magazine,dealer or Joe Blow told them to.