horsepower (as a measure of the breadth of the bike’s most usable powerband). Finally, along with each chart is a quick analysis of what it all means. BASIC DYNO ETIQUETTE MXA breaks in every bike at the track, and then takes it to the dyno. We test every bike on the same dyno and have used the same dyno for a decade. We try to control all the factors to ensure that we get the most accurate dyno runs possible— and we return to the same dyno when it comes time to test pipes, pistons, port jobs, ignitions or fuel. You cannot make comparisons from different dynos; you have to use the same one if you want valid numbers. As much time as we spend dyno- ing bikes, you would think that we would rely heavily on the results. We don’t. We still test the old-fashioned way. We race. We switch bikes. We fill out test reports. We let our emotions run free. Then—and only then—do we consider the cold, hard facts of the dyno. Why do we downplay the dyno’s influence? Because we’ve ridden bikes that were roaches on the race- track and jewels on the dyno. These are called “dyno queens.” We have also ridden bikes that could barely move the needle on the dyno chart but worked wonderfully on the track. We like to think that we can use the dyno to confirm what we felt on the racetrack, unless it doesn’t confirm it—in which case we go with our feelings. Sadly, this story isn’t about our feelings, but about the cold, hard, statistical facts of the dyno.
ANALYSIS Everybody loves charts and graphs—except the losers
In the process of testing motocross bikes, MXA takes months to form an opinion. We live with the bikes, fix the problem areas, struggle with the bugaboos, race them, sound test them, weigh them and dyno them. In this article, we have gathered to talk about MXA’s dyno runs on the 2013 250cc four-stroke motocross bikes. The following information is based on MXA’s dyno runs of the six major 250cc four-stroke motocross bikes. We isolated the horsepower ratings at 8000 rpm, 10,000 rpm and 12,000 rpm to get a graphic display of what the power looks like at three major points on the curve. Then we graphed peak horsepower, peak torque and, most important, we measured how wide the rpm range was where each bike topped 35