Originally Posted by Greg58
I have a drill set with a pen type drill handle, the solder and drill method is what I do also. The one thing I have learned is everyone of these engines are different, what works on one may not on the next. On my 48cc with the cns2 I'm at a 66 drill size, that's where the plug color got right. On other bikes I've tuned the stock jet (71 I believe) was OK. These things are very simple, that's why they drive us crazy!
So far all of my 66cc engines with NT carbs have liked a jet drilled with either a #72 or #73 wire bit, my RT carbs have both run perfectly with the #70 jet that came with them, only slight low rpm 4 stroking and zero under throttle or at cruise speeds and a nice medium brown spark plug electrode, climate and altitude play a part in all this jetting stuff also, so yes it is not universal when tuning the carbs, it's a matter of running the engine and figuring out what it needs and like the best based on how it is set up and with what exhaust it has which has a lot to do with the amount of air that can flow through the engine.