need jet advice

I had to drill out the main jet on my cns2 on a 48cc grubee to get it to run right. The stock on mine was a #70 drill bit, I started with a #69 and doing runs and plug checks till it ran right & the plug was light to med. brown. I ended up at a #64, I know it sounds big but with the sbp air filter thats what it likes. Biknut did alot of work on a 66cc that may help you out.

http://motorbicycling.com/f34/omg-i-have-tune-cns-help-30169.html

Here's a cheap set that will get you by.

Amazon.com: 21 Pc Mini Drill Bit Set Tools Precision Tool Model Car: Home Improvement