gas oil ratio

When you order your motorized bike kit the manuel says to put 16:1 mix and than 20:1, well I use 40:1 and It runs great. My first tank of gas was 40:1 mix. Should I use 20:1 or 40:1

what is the proper oil/gas ratio for breaking in a 66cc china girl ? I've heard 24:1 or 32:1 ............... but we all know too much oil is bad and too little worse ............... Ive been using 50:1 but its a little too rich it bogs down (so much smoke also) ....... i use synthetic oil...