coil you can test if you have a coil tester but doubt you do. CDI cant be tested. could also be a pick up coil on the stator, ignition switch, kill switch, tether if it has one.
Sometimes when bad parts heat up they fail. I have seen this with the cdi. Be very aggressive when checking your connections. Do you lose spark after it has been run for a while or at certain temps?
something is still wrong in the carby or the fuel lines to the carby
did you check the float level before assembly
Change the plug leads to a better quality and replace the plugs
is the exhaust system clean and not blocked with carbon or rust
White smoke would be water. Blue smoke would be oil. Was the engine overheated ? If so probably a blown head gasket. Check oil and water to see how low they are and how milky they are.
guessing you changed the spark plug? .. you can fry the coil from heat...I used to wrap coils in rags when I tested them on a coil tester to try to make them break down from the heat quicker. It worked too.