Motorcycle Repair: 78 hondamatic, air fuel ratio, speed jets

Question
You answered a question for me before about the air cutoffs.Well i replaced them and that did not fix the problem.I am getting a backfire on the left side and not the right.Cleaned both carbs and it is still doing this.The left spark plug looks different then the right looks like it might be leaner then the right one which looks perfect burning.I need some help

Answer
Michael, backfiring is normally caused by a lean mixture.  The air fuel ratio is too lean to ignite when the sparkplug fires.  The raw fuel is pumped into the exhaust system and then gets ignited by the hot exhaust from the other cylinder.   The air fuel cutoffs, prevent the problem by shutting off the fuel completely so it doesn't load up the exhaust.  

You are looking for something that is leaning out the mixture. Either the air cutoffs are still not working, or you have an air leak that is causing the mixture to go lean.  The float level could be too low in that carb or the low speed jets are partially plugged.

Regards
Rich