Vehicle is smoking when changing gears

The car is driving smoothly and it is having power but it is smoking. The smoke is white and is not too much. It is giving out smoke during the first and a second gear. I changed the valves.

A second problem occurred when I sprayed the carburetor with a carburetor cleaner, I sprayed it whilst revving it hoping that it will stop smoking but instead it lost power. Now I have to do a lot of downshifting.