Need Help!

http://motorbicycling.com/f4/motorized-bicycle-carburetor-pictures-how-install-195.html
This might help to get you familiar with the carb.

Sometimes the throttle slide barrel thingy will stick. Take your filter off look in the back of the carb to see if it moves without sticking. You can get a clear look at it that way. The needle clip needs to be on the second notch from the top. That is where most of them work good at. If the throttle barrel body sticks you can gently remove any burrs you might find with Emory cloth. [a fine grain sand paper]

A 16 to one oil mix is too rich try around 24 to one.

Your carb may have something in the needle seat be sure you are using a fuel filter as the smallest fleck of trash there will upset it and make it overflow.

Don't over tight the throttle cable housing ether as it can make the throttle barrel stick.

What cc engine you have.... I think engine is running on more rpm than it should run on.... and yes try the oil thing also see it could help a little or not... it will definitely reduce the white smoke from your ride!!!