seriously.. can sumone answer my ?.. this is a serious ?.. why is it that dirt bikes top out faster than quads.. even if the quad is a 350.. and your going against a 125 cr..?? y is it.. is it just bc of the wayy biggerrr sprocket.. or wht?? can sumone please let me no?

 

I think the bigger sprocket is needed because the wheel is bigger. Weight and friction have some to do with it being faster. A dirtbike weighs less and only has 2 skinny tires touching the ground. Plus the YZ, CR, KX, & RM engines are just awesome. They have a power valve that helps also.

I'm not an engine builder, so I don't understand how they do it, but I'm sure the engine design helps alot. The stroke of the crank will determine how an engine performs, and engine builders can tune the engine for the purpose they are trying to achieve. Dirtbikes are made for one thing - winning motocross races. A 350 quad (Warrior or Raptor 350) is designed for slow to mid-speed trail riding. A Banshee is also a 350cc, but it runs completely different than a Warrior 350 and is a whole different beast than a 4-poke Yamaha 350.

 

I'm guessing it's the weight difference.

For instance, the YFZ and YZF 450's have practically the same motor, but the YZF being substantially lighter is definitely gonna have the power to weight advantage...

..but I'm not a mechanic..this is just my opinion...[img]i/expressions/face-icon-small-wink.gif[/img]

 

I think its mostly weight and secondly dirtbike motors tend to be tuned to make more power. Ive found that if racing a 2 stroke dirtbike on a quad you need about twice the motor to win if your on a 2 stroke or a newer 4 stroke or 3-4 times the motor if your on an older 4 stroke. My Warrior 350 will almost keep up with a CR125. My modded 91 LT250R was faster than a RM125. My 86 stock LT250R was a bit slower than a RM125 but was stock and slow for a 250 2 stroke. Never raced a 250 dirtbike on the LT500R. Pretty sure my 87 would have won on pavement but I dont consider that a real race cause its not what they are made for. Offroad its hard to say cause the 500 would spin its wheels on dirt all the way to to top speed so it was not making use of all that power.

 

its can only be three reasons. 1 dirt bikes are lighter then atvs, 2 the back tire is taller 3 dirtbike engines have a small difference from atv engines i know the honda 450 quad has two rings on its pistons and makes more torque but less hp then hondas 450 mx bike which has one ring on its piston aswell as a lighter rotating mass.

 

ok thank you very much.. but woulndt u say tht quads have more torque than dirtbikes.. so saying that if i went up against my friends cr 125 on 1/8 mile straight away .. would i prolly win?? but if it is longer like 1/4 mile or 1/2 miles straight away .. he would prolly win>>??

 

Most likely you will lose. He weighs a ton less than you, that will more than make up for the low end torque advantage by itself. You prolly dont have much more power overall and the bike is geared to use its power optimally. You originally brought up a 350 so I assume a Raptor/Warrior. Mine is tuned up good has a few mods and still wont quite keep up with a stock CR125. If you want to race dirtbikes you need to buy a fast quad and make it faster or get used to losing.

 

The power to waeight ratio on a dirtbike is much different than a quads. The dirtbike has a better power to weight ratio. this also means in a drag race they tend to spin alot off the start. This is also due to the fact that they have less surface area on the ground. So on an 1/8 mile track maybe. But on a 1/4 you better be ready to eat dust. Then again dirtbikes are tuned for the track and are geared differently so even if the dirtbike was a 250F and the quad was a 350 or 400 then the dirtbike would still win. Just because of those factors.

 

quad engine has to spin 2 tires, dirtbike only has 1. that and the weight difference would be my top reasons...only my opinion though.

 

ok wht would u say if i got a jet kit for it, k & n air filter, better reeds, big gun evo x exhaust, bigger piston, a smaller rear and a bigger front sprocket(for more top end) and a stage 3 hot cam??? then wht would u say??.. do u think i could take the cr 125 then??