The bike now Idles perfect with the carb on the third notch! Much more responsive in mid throttle. The engine still 4 strokes now and then but It did help the over all performance. I used .75 mm or .0295in bit. I was surprised that I could just use my fingers and the drill bit. Just the slightest amount of material. This mod was done to my 48cc Grubee, slant head. I a run a E3.12 sparkplug. I have also port matched the gaskets and cleaned up and polished the chamber in the head. I can also reach my top speed quicker. Anyone else have success with this?