The fact that it was flooded and would not start when you went to buy it should have been enough to walk away.
The flooding problem is going to be carb related, a problem with the needle valve/seat or float. You could also have air leak trouble if it over revs.
Unless you know how to strip, check, and reset carbs I would leave well alone and take the bike back.
If the carbs are this bad, what other problems are going to come to light later??
Should have got a Honda
