Dirtbike vs Quad motor

[BLU82]

I read in my transworld motocross magazine that the 09 kx450f bike makes 55 horse stock! What is so different between the bike motor and the quad motor? I know the cams are and the angle of the piston is different but that would'nt account to nearly 17 hp. Could be that much of a difference in drivetrain loss, or is something else going on?

[CTmxyfz]

prolly different crank and stuff like the yfzs and stuff. I havent torn into the bottom ends of the kfx yet or the kxf but i do know of course that the pulser coil location is definately different. Hense the custom BCS stator covers when switching to carbs. Im sure the head, piston, crank, and we know cams are different.

Its been heard that stewart is actually using the GYTR YFZR head on his dirtbike

[LT-R450 131]

motors put out different HP do to weight like if you would put a car motor in a quad it would have way more hp than it would in the car...and also putting a 55 hp crf motor in a hybrid quad would put out less hp

[rider250ex]

Hp at the crank wont change no matter what you put it in. Im sure the way the fuel injection is tuned makes up for some of that power, along with the restrictive intake.

[chipworkz]

Originally posted by LT-R450 131
motors put out different HP do to weight like if you would put a car motor in a quad it would have way more hp than it would in the car...and also putting a 55 hp crf motor in a hybrid quad would put out less hp

WHAT???
How does the weight of something effect the horsepower of an engine. The power to weight ratio would change but not the horse power.

How does the weight of a vehicle have any effect on a vehicle when it is strapped to a dyno?

[Drewltr450]

Alot more stuff to turn. Huge car wheels Huge axle Huge driveshaft.

[trx250rider]

yeah the weight will not affect the hp at the crank...the cr 250 r puts out a lot more hp then the trx 250r also..i read somewhere that the quad motor came detuned from the factory, this is mostly porting and reed setup...