A YZ125 will run around 75mph, give or take. I know that it can stay with a stock DS650. A 250 should be able to hit around 100mph and a 500..........well, you do the math. Trust me, a 250 has more than enough power. How many motocross racers or freestyleist do you see with 500's?????? They are all riding 125's or 250's....for a reason. HAve you ever sat on a 125 or 250??? Two of my riding buddies have YZ125's, one is a 95 and the other is an 03. They are both around 5'8" to 6' tall. They have a hard time touching the ground. One of them weighs around 230lbs, and he is the one that edged out the DS. All he has is a ProCircuit platnum pipe and race silencer. He has a hard time keeping the front end down. Unless you are just desert racing wide open, then a 500 is OVERKILL!!!!! Stick with a 125 or 250, trust me. I have an old '71 Yamaha DT250. Pretty much stock with a .40 bore and mx pipe. It is even air-cooled it is so old. The whole thing is made out of steel except fot the plastic fenders. That thing will hit about about 90 mph

 

I am 5'9 170lbs and a very experienced bike rider, riding since the age of 12 and my 125 hauls me around just fine. You don't need a 500, you will kill yourself guaranteed!! One of my friends was 6'3 280lbs and he could not keep the front end of the CR500 he owned down, he had difficulty controlling it a lot of the time. Like the others said, a 125 will suit you well, a 250 is pushing it. The CRF 450 runs like a CR500, I was shaking after I finished riding my friends that only had exhaust as a mod. Not to mention my old roomate who never owned a dirtbike, owned a 1100 harley and thought a CRF450 was a joke, bought it and ruined it his first time out...haha!

 

ok heres what i think. u cant be scared of ur bike cuz u will hurt urself. when i got ma first 250R i was scared of it but once u learn how to manhandle the bike and know it wont hurt u because ur in control ur all good. and i would get the hond 450. i dont really like kawasaki and they arent half as reliable as a honda.

HONDA FOR LIFE.

i mean look ma bike is a 1972 its honda and it is still runnin(ma xr 250) i mean how many kawasakies do u see runnin that r that old

 

going from a honda 480mx bike that was made back int he day. going to a kx500 u would die. ive rode bikes quads since was 5 im 16 now and i rode a few 500s in the dya im 6'1 160 lbs and i am scared. the 125 is a good machine but if u gonna jump and do stuff like that go w/250 u will be better off downt he road. and dont worry a 250 has plenty of power. seen a guy with a ktm 250 start at a dead stop out at a bottom of this hill/jump thing and 125s clear it but have to start att eh top of it. go downt hen up the other sid.e this guy went to the bottom stopped and cleared it liek ti was nuttin. u jump the hill inot a doulbe type/step up jump. so a 250 will have plenty of power

 

Okay look as a fellow kid( i am fifteen too) listen to me, i personally have not even rode a 250. butt. a 125 should have plenty of power plus i am 6' and i can barely touch teh ground on a 125. my cousins Yamaha yz100 is fast enough to pull a mojave and a blaster in a drag race.

 

AND MY PARENTS SAY I HAVE A DEATH WISH[img]i/expressions/face-icon-small-wink.gif[/img][img]i/expressions/face-icon-small-tongue.gif[/img]

 

man ur an idiot sexybeast im 14 bout 6 2 165 lbs and i have been riding four wheelrs and dirtbikes awhile. one u know that the size of the engine doesn't mean how fast itll go. 2 if you dont have the knowledge of riding a 500 at yu age and size and jumping it would be suicide. I have rode a down the blockon a 500 and only had the ***** to get in in third. Never the less jump the thing. Whut HA2 said ill buy it when u crash for when i get way older (4yrs)

 

i have a 2001 kx500 and i'm 5'9' and 200lbs and been riding bike's,atv's for over 20 years. the kx is better for open trails and area's. it jumps great but it really has too much power for jumping. a 125 or 250 would be alot better. i had my 500 slam me on my butt in third gear and took out the subframe and fender from getting too much traction in the mud. my 250 is alot better for tight trails and jumping and alot more forgiving.

 

theres this guy that runs our local harescramble series and he's always ridden a cr500. and the trails you have to push your bars through

 

im 16 6'1 205lbs and my CR250 has plenty of horsepower...IMO u'd be better off on a 125..i can touch the ground fine on my bike..as for top speed it doesnt matter how big the motor is nessecarily, u can always re-gear it to run on top or bottom end.