Using an O2 sensor to tune an engine is only worthwhile when the engine is 100% spot on running perfectly. Remember an oxygen sensor senses oxygen, not carbon monoxide, not CO2, not hydrocarbons etc. A cylinder misfire results in unburned fuel and air so your oxygen sensor will see high O2. Are you going to assume lean because of this? O@ sensor tuning is only for fine tuning a properly running engine. Using it to diag a drivability issue will send you down a rabbit hole. Since you are carbureted, don't bother. Fix your timing and then play with your carburetor.