We like power. We often think of our dirt bikes from a perspective of how powerful they are. Visit your local race track and you might hear talk about what bike has more power. Visit manufacturer websites, dirt bike magazine reviews and “shoot outs” and you’ll certainly see some discussion on power. Power is indeed important, but will a more powerful dirt bike make you faster? The answer to this question is a resounding “maybe”. So, before you conclude that you need to run out and grab a more powerful dirt bike, read on for some insight.
First, you should realize bikes are designed and tuned for their intended purpose. You can find dirt bike models for casual trail riding, aggressive trail riding/racing (such as enduro), skills based riding (such as trials), long distance desert riding and motocross/supercross. Keep this in the back of your mind as the discussion continues.
Let me be clear on what power really is. Folks talk about it and they know that an engine produces power, but do they really understand what it is? To some degree, of course. Power is often discussed in terms of Horse Power (HP) but Horse Power is a specific unit of measure. Horse Power is equal to 550 foot pounds per second (approximately 746 watts). This means that a 1 HP engine can produce the equivalent of 550 pounds of force acting on a one foot lever arm for each 1 second in time. You can imagine this acting in a continuous circle having a radius of 1 foot.
The part of this that is missing is that everything takes time. No engine reaches its fully rated Horse Power the moment the throttle is opened. At idle, an engine produces a small amount of power because there is a limited amount of fuel and air entering the combustion chamber. As the throttle is opened, more fuel and air is introduced which results in more combustion energy and therefore more power output. Again, this takes time. Realize that engine designs can be altered to either speed up or slow down the time to reach full power.
Going back to the “intended purpose” concept, a motocross bike would be designed to reach maximum power very quickly where as a trail bike would be designed to reach power more slowly. In these two examples, we should see that it is all about the need for control. A very quick motocross bike would difficult to handle in tight, rough mountainous trails. Obviously there can exceptions to this as there are many riders in the world who are not human and who exhibit amazing talent. For most of us though, trying to navigate very tight, gnarly trails on a hard hitting mx bike would make for a lot of work. Realistically, you would probably go faster on the more mild trail bike. Conversely, trying to win a motocross race on a trail bike would be a big fail.
With this last explanation, I have strayed from the idea of power a bit (with regard to being faster). You see, there can be two bikes of equal power output each having very different characteristics of power delivery. One achieves power delivery very quickly and the other more slowly, by design for the intended purpose. Let’s move on…
Let’s stick to one venue as an example: motocross. I want to point out that most motocross bikes are very quick. Even the smallest bore motocross bikes are very quick actually. Put an expert skill level 10 year old on a modern 85cc two stroke or 150cc four stroke and you would see these bikes are very fast. Now, put me on a 150cc four stroke or an 85cc two stroke and the bike will be severely under powered for my massive 225 pounds. Put me on a 250cc four stroke and that will be better but likely still not good enough. Obviously, I would be faster on a 450cc four stroke because the smaller bore bikes simply do not have enough Horse Power for a rider my size. Now, consider the expert level 10 your old kid on the large bore bikes (assuming he could fit). The likely hood of him being any faster is basically zero. Why? Because all the increased power is of no benefit. If the 250 has more than enough power already, then a 450 certainly would be pointless.
As I said once already, there are exceptions. More power does in fact provide the potential for more acceleration. However, too much acceleration can be a detriment by making it difficult for a rider to handle the bike, thus actually slowing the rider down. Furthermore, if a bike already has more than enough power to pull a rider’s weight, it is unlikely a more powerful bike will make the rider faster.