You didn’t say, so I’m going to ask…are you turning off the choke after you start it and let it run for a few seconds? This sounds like the engine is running too rich after starting. You might want to also check the linkage between the choke lever and the choke plate itself. You might THINK you are turning the choke off but it still might be set. You can usually see the choke plate by removing the air filter housing (not just the air filter). It’s usually a butterfly plate that pivots 90 degrees when you “choke” the engine and should be parallel with the airflow when the choke is off.
If that’s not it, you should replace and gap the spark plug (you said spark plugs…but I believe this engine only has 1). You’ll need a spark plug socket and a spark plug gap setting tool (they around $5). Someone should teach you how to do it the first time, as they are really sensitive. Note the old plug when it comes out, it should be dry and tan in color ideally. I little bit of dry black is ok too. Oily and black and that means you have oil in the combustion chamber. Not ideal but might be ok. Replacing the plug will tell you a lot when you look at the old plug.
Hoping one of these helps you out.