Does a toy top weigh less when it is spinning?

To a certain extent yes, if you take aerodynamics into account. Specially made top can deflect air to provide a lift force. Exaggerated example is a helicopter.

A better example though is Frisbee. But it's not because the mass reduced or something is done to gravity, it's just a force exerted by surrounding air. 

Why does a clockwise-spinning top suddenly spin counter-clockwise right before it stops? The phenomenon is caused by the fact that the top exhibits unstable rotation in other axes besides the one it's spinning in.  

As the top loses momentum in the key direction, and it falls over, the spin in one of the other directions can be transferred into the stable one.  It suddenly briefly rights itself.

You can see it even more clearly when you've got something designed to exaggerate the instability.  A toy called a "rattleback" does just such a thing:

http://upload.wikimedia.org/wiki...

You can see that just before it reverses direction, it wobbles (pitches).  That energy is then transferred into spin in the direction in which the spin is stable.


https://physics.stackexchange.com/questions/33866/does-a-toy-top-weigh-less-when-it-is-spinning
https://www.quora.com/Why-does-a-clockwise-spinning-top-suddenly-spin-counter-clockwise-right-before-it-stops