Hey where is our HP?
 

I am sure everyone will look at this :D

I started wondering what the difference was between this and half of the Ninja 500 that I am going to pick up next week.

I think it is basically two of our motors but the specs I have read put it at almost 50 rear wheel HP. The specs for the KLX are closer to 20 if that. So where is our 5 HP?

Remember too that there is somewhat of an exponential rise in HP with displacement, so it's not just adding the power of 2 KLX engines together. Plus the kind of power that's designed into a Ninja 500 engine is not the kind of power, and specifically not the powerband, that one would normally want in a DS dirtbike. It truly is a good example of the old apples-and-oranges comparison.

The most important factor I think is the bore to stroke ratio. The Ninja has 74x58mm, vs 72x61.2 for the KLX. This makes the Ninja engine a higher rev one, mainly due to larger valves. This comes with an attendant decrease of service life, which might not be so noticeable for the Ninja500: a street bike typically does not experience the same duty factor as a dirt bike, specially a 250cc one.

Thanks for the insight. Somewhere I found a power curve for the Ninja and it was not hugely different than the KLX as far a where the power peaks etc.

I thought wrongly they were the same bore and stroke. Bigger valves will do it. More air more fuel more power.

I actually don't, at this time, need more power out of the KLX. I was really curious and this clearly is the answer.

TNC, I had never heard of the exponential rise in HP with displacement.

I guess if you are always higher in the power band you will decrease service life. More friction more wear. They have been know to run a long long time with maintenance.

I think the KLX even on the road will see more wear on average. You have to be a bit higher in RPM to keep her going. I was able to loaf around at 3k on the Ninja with no lugging. I have to be 4K with the KLX and if there is any load 4.5k is better.