its a combo of the intergear notch/dist lower shaft tang rotational slop and or the springs. if you are not twisting hard enough to get into the springs then it is all intergear slop. it does cause spark scatter at idle when timing it (spark jumping) & it it indicative of a less than a spot on perfect eng but might be left alone as is for now. People have reportedly resolved it with a 1/2" ID setscrew collar slipped on the shaft but I would rather have my welder build up the tang for a dead on rotational rather than the axial solution with the collar fit & seperately, further up, adding shims above the plastic collar with the roll pin to reduce the lower shaft axial play to .005". speedway mtrs has a kit of dead flat thin shims for $10.