at my last race almost all the quads there didn't have a airbox, just ran the filter right to the carb. to accomadate for the extra air how many main jet sizes should i go up.

y2k400ex
www.400ex.homestead.com

 

You don't say whether you have an aftermarket filter or not. Assuming you do not, I'd go two sizes fatter just for the box removal. If in fact you DO have a K&N or similar filter & haven't jetted for it then I'd go up three sizes & test/read the plug. Always best to err on the side of rich than lean, so if the electrode/insulator is black, drop a size.
I just finished loading a pic of my Split Fire plug that shows the coloration for proper jetting. If you need to see it email me.
BTW, I tried to pull up your site, but Excite could not find it, Also failed to open it from your profile. ??????