I would say bad rings or head gasket. Does it smoke at all? It might be really faint and hard to see, so you could shine a flashlight next to the exhaust to see it better. Also check that your choke butterfly is open all the way 😉
BUT it is normal, some engines smoke on startup naturally or due to age, etc. All of my riding mowers smoke on startup, but there's nothing wrong with them 🤷🏼♂️
Ok, it the gov is adjusted, that's a bad internal governor. Also, what color is the smoke? Blue is burning oil, black means it's running rich and the carb probably needs to be cleaned and adjusted.