got the fuel to oil ratio mix right 20 to 1 or 32 to1?
4 oz. of oil to 1 gallon of regular gas for 32 to1 mix.
will the throttle slide open all the way? do you know which way the choke is on and off? lever up choke is on lever down choke is off.
spark plug gap is it at 0.020"
I don't have a lot of info to work with.
new engines take a while before they run good they need to broke in first and will sometimes run crumby until they are broke in.