The reason they both put out the same horsepower is that the Raptors engine is very mildly tuned which means it would gain lots of power from performance stuff like cam, high compression piston and stuff like that. The YZ is a HIGHLY tuned engine made specifically for MX Motocross, and it won't benefit from cam, and high performance piston and stuff like that.

 

With the power to weight ratio of the 426, you could probably gear the thing to have more top speed than any atv easily.

 

The YZ is a racing motor. The DS & Raptor are for fast riders, but still not pure racing.

Talk to the racers, both expert and begginer, and ask what last longer without work/maintenance, an XR400 or YZ400? But which is more powerful?

That dyno is for a YZ400 I think. In '99 it turned 426, and got faster. In '00 and again in '01 they made it faster again.

The YZ250F, 4-stroke, revs to 13,500! Think that will be as reliable, or trail-rideable, as an XR250? Nope, but it will tear-up the race tracks.

Yamaha could have made a YZ426 quad, and been faster than a Raptor, but the majority of the ATV riders don't race competitivly enough to justify the work required that goes with it. Actually, most ATV riders, even sport riders, don't really seriously race at all.

Just my opinion.

 

My dad has a raptor 660 and I have a 426 and I smoked him, and my dad loves speed but my 426 kicked the raptors *** in a drag

 

They established that 15 years ago man lol

 

Oh well

 

Those 2 stroke big bore Motocross flew. They where called open Class for Baja type riding never meant to go around tracks.

Its Yamaha version that competed against the CR500,RM500 and KX500.
The 250 class are scary and race the new 450 4strokes so just imagine the 2 stroke 500s.

There about 50hp and weigh only 240lbs so no ATV would touch one not even the old 500 Kawasaki and 500 Suzuki Quadzilla 2stroke ATVs with the same motor.
My guess it they do 80.
A ATV may go 80 as well but it will not get to 80 nearly as fast ,I can guarantee you that.

I only rode a Honda CR500 but I imagine the YZ426 is the same thing pretty well.
Hang on tight is my advice.

 

the 426f was a 4t that was replaced with the 450f. It was not a 2 stroke.

 

OOps I was thinking of the YZ490. Sorry.
Better drop my speed and acceration figures way down then. LOL

 

Think about it, even a light sport atv still weighs a whole lot more than any dirt bike. The bike doesn't even need to have as much power to be faster, power to weight is very important when its 250 lbs vs 400 lbs. Its less important the heavier the machines get, more power will prevail in that case and with 1000 cc 4x4 quads, massive weight gets overcome by huge v-twin power. The Sportsman 1000 has a claimed 88 hp, for example.