Motocross/Dirt Bike Help! (Not Mechanical)?

I am looking for more power in my motocross bike, it is a CRF250R, I want more bottom end to top end, a CRF450R is a bit big for me, seeing that i am only 13 and 5'2, but I am open to suggestion.

Do you know if slip on mufflers make any difference, i can't afford to blow $1000 for just a few hp on a full system.

If you do suggest a motocross bike, keep in mind that i want a 4 stroke, 2 stroke are a thing of the past (sorry 2t lovers) and i want motocross not enduro or offroad.

would a 450 be out of the question?
Is a big bore kit ok?
what should i doOOO?

thanks a million, no wait a bazilion!!!
(bad joke, i know)

I want more power, not more speed or acceleration

'I want more power, not more speed or acceleration'
' I want more bottom end to top end'
Very confusing statements, but your CRF250R's power curve has already a great low end and top end to begin with.
Sounds like you want more hp and the way to get it is to go the way of a big bore kit.
http://www.powersportspartsonline.com/Sh...
http://www.powersportsuperstore.com/Prod...
Good luck on your upgrade.
Good riding.

the Athena big bore cylinders are probably the best bang for the buck, cost about the same as a full exhaust but gives much better performance gains. honestly though, if your only 5'2 you probably don't weigh very much and the bike has more than enough power already. if you're gonna spend money on anything, a motocross camp would make you faster than adding horsepower

so you want more horsepower and you
want it from the bottom to the top.
the only way thats going to happen
is if you spend a hell of a lot of money.
how much money do you have to spend.
i would say that to do what you want to
do would cost at least five thousand dollars
parts and labor. you are not ready for a 450
yet. you need to ride that 250 of yours for
another 2 or 3 years before moving to a
bigger bike.

have you tried changing the sprockets to a different ratio? that would be a cheap fix for the time being. besides, a 450 would end up taking you for a ride rather than you being in control. keep with 250 for a while longer. Get some more practice and move up when ready. remember, anyone can go fast in a straight line, its when you turn the corners and ride the bumps fast that requires the skill