What do they mean by 28 Horse Power?

[Sparks425Ex]

Everyone knows that a 400Ex has 27 or 28 HP.

I was just in a convo about this and we weren't sure if it was 28 HP (At The Crank) or 28 RWHP

And when they talk about a CRF450 producing 53 Horse power is that at the crank or at the RWHP

[UglyMotha™]

the ex's 28 is taken at the rear wheels but i dunno about the crf

[Natertot426ex]

I am sure that they would measure everything at the rear wheels because that is where all the power is transfered.

[Dirt]

But on a Bike? hmmm...

[jhr400EX]

I am almost positive that the crf's reading of 53hp is taken at the crank.

[Dale512]

Im going to go with Josh on this one and say the CRF is taken at the crank.

[Bretmd94]

You sure the 400ex's isnt at the crank also? Most companies that sell cars and bikes always take the HP rating from the crank. Ive seen dynos with 400ex hp at around 25. And with exhaust they get up to 28-29.

[H_W]

When I bought my 400ex from the dealer, it came with a paper that lists the specs. It has horsepower at 34, I have seen others post about this also. I believe that is measured at the crank and the 27 or 28 is at the rear wheels.

[KY Woods Rider]

Originally posted by H_W
When I bought my 400ex from the dealer, it came with a paper that lists the specs. It has horsepower at 34, I have seen others post about this also. I believe that is measured at the crank and the 27 or 28 is at the rear wheels.

Yep, the "Certificate of Origin" that I received when I bought my EX says 34.2 horses. That is crankshaft horses. The 27-28 HP that most people quote for the EX is measured at the rear wheels (what is actually getting to the ground).

As for the CRF, I'm pretty sure that is rear wheel horsepower. However, it won't make nearly as much rear wheel horsepower in a quad chassis. The reason is that it doesn't take as many horses to turn a bike's rear wheel, it's just a tire, hub, rim, spokes, sprocket, and rotor. In a quad frame there is more weight to turn before the power gets to the ground; two heavy tires (compared to bikes), two solid aluminum wheels, two hubs, sprocket, rotor, and a fairly heavy axle. In a quad frame I'd say a stock CRF motor should be putting somewhere around the mid 40s to the ground. However, I haven't seen a CRF motor dynoed in a quad chassis, so that is just a rough estimate.

[BigAl]

I'm pretty sure the 50-55 hp numbers for the CRF and YZF are at the crank specifications.