Some people are certain that the new four strokes are going to be a great addition to our sport. Some people are sure that it will mean the end of the world. Some people are wondering about the advantages that the four stoke will offer the trials rider.
While it is true that we won't know for certain how they will perform until they get here, I found this description of four stroke power, written by Cycle World's Technical Editor Kevin Cameron, very interesting.
"The major advantage of the four stroke is that its power, as the throttle is initially opened, begins near zero and increases smoothly, especially in mildly tuned engines with short cam timing. In the two stroke this is not possible, because at low throttle, fresh charge is so diluted by exhaust gas left from the previous cycle that it cannot at first be ignited. When it fires, (two-stroke) it does so only after several cycles have delivered enough charge to be ignited. Torque therefore increases in chunks, as eight-stroking becomes four-stroking, and four-stroking jumps to steady firing-torque doubling at each step. Devices such as exhaust power-valves have helped, but this problem has never gone away. Therefore a rider on a four-stroke can safely send power to the rear tire sooner, and so begin acceleration earlier."
Kevin Cameron - Technical Editor Cycle World Magazine - February 2003