It is normal for the tappet to rotate when it is being lifted, though there is nothing wrong if it doesn't. You might check whether it rotates all the way around over a few turns, or rotates part way and then slips back to its original position. The latter would indicate a bent tappet.
It is also normal for some air and fuel to be pushed back through the inlet port and carburetor during the early part of the compression stroke, when the inlet valve is still intentionally open. It should not be a lot of gas, but it is always quite noticeable. Normally the air cleaner traps it so it does not cause a fire hazard.
Does your engine start easily and run properly?
