Yeah, dustin has a point.
Jetting is more than a number. What you're trying to achieve is an ideal air/fuel mixture.
Too much fuel (which is what happened when you drilled out your jet) will make you bog, or foul plugs, or not run at all.
Too much air (too small of a jet) will cause it to burn too hot. Sometimes you'll go faster running lean, but this isn't what you want. Too much heat and it'll eventually seize, likely ruining your cylinder/piston. This is bad.
So you want to find the perfect balance. You do this by doing plug chops with different jets. Plug chops are easy, but I don't want to explain them here, because they've already been explained very well elsewhere. So your homework is to go find them. Search the wiki, search the repair forums, search the performance tuning forums.
In fact, here. A link : http://www.mopedarmy.com/wiki/Plug_chop
And another good one: http://www.mopedarmy.com/wiki/Fred%27s_Guide
If you post a question, and it can be answered by that second link, then you'll probably either get a bad response, or no response. Everyone should read Fred's Guide at some point.
Wheee.... Coffee makes me type lots....