Instead of drilling the jets, I recommend you follow the advice posted in the following threads.
http://www.chinariders.net/showthread.php?t=6501
http://www.chinariders.net/showthread.php?t=6528
Mikuni jets shouldn't be very expensive. You can buy several jets, both larger, and smaller, than the jet recommended in the threads listed above. In this manner you can experiment with several sizes of jets to determine which works best for you.
__________________
Spud
"Never argue with an idiot. He will drag you down to his level, and beat you with experience."
Mark Twain
2015 Zongshen ZS250GY-3 (RX3)
2006 Zongshen ZS200GY-2 (Sierra 200)
2005 Honda XR650L
2004 Honda CRF250X
1998 Kawasaki KDX220
Mods made to my Zongshen ZS200GY-2:
http://www.chinariders.net/showthread.php?t=6894