  The effects of varying the spin-orbit and tensor components of a realistic
interaction on $M1$ excitation rates and $B(E2)'s$ are studied on nuclei in the
$0p$ and $1s-0d$ shells. Not only the total $M1$ but also the spin and orbital
parts separately are studied. The single-particle energies are first calculated
with the same interaction that is used between the valence nucleons. Later this
stringent condition is relaxed somewhat and the $1s$ level is raised relative
to $0d$. For nuclei up to $^{28}Si$, much better results i.e stronger $B(M1)$
rates are obtained by increasing the strength of the spin-orbit interaction
relative to the free value. This is probably also true for $^{32}S$, but
$^{36}Ar$ presents some difficulties. The effects of weakening the tensor
interaction are also studied. On a more subtle level, the optimum spin-orbit
interaction in the lower half of the $s-d$ shell, as far as $M1$ excitations
are concerned, is substantially larger than the difference
$E(J=3/2^+)_1-E(J=5/2^+)_1=5.2~MeV$ in $^{17}O$. A larger spin-orbit splitting
is also needed to destroy the triaxiality in $^{22}Ne$. Also studied are how
much $M1$ orbital and spin strength lies in an observable region and how much
is buried in the grass at higher energies. It is noted that for many nuclei the
sum $B(M1)_{orbital}+B(M1)_{spin}$ is very close to $B(M1)_{total}$, indicating
that the summed cross terms are very small.
