i have a 99ex and im gettin 440 kit and i was wondering if i will be able to keep up with the new 450s and if not how close would it be and would a sprocket kit change it any... the 440 bigbore kit includes this - Namura 440cc Big Bore Piston, Rings, Circlips, Pin, 440cc Hi-Performance Gaskets, Advanced 440cc Sleeve, Magnum Hi-Performance Rev-Box, Magnum Stg. Performance cam. I also have white bros pipe and uni airfilter with no airbox lid and im also getting the white bros header pipe soon.With all that would i be able to keep up with 450s

you should be able to keep up with them as long as they stay stock.
you can regear to gain top end speed but you loose low end torque

If the machines are all stock excpet yours fr sure, you will beat the 660r but will have a major battle with the 450's, it also depends how good the kit was installed.

i would thik it would if the rest are stock and you have the equal amount of experiance as them

lol, High-Performance Gaskets. [img]i/expressions/face-icon-small-smile.gif[/img][img]i/expressions/face-icon-small-wink.gif[/img] I think you should have no-problem keeping up with the 660R's and YFZ's.. i dont know about beating them. My friend has a 430ex and he isnt close to a YFZ in a drag race in sand pits..

You'll need some head work.