  In this paper, we compute the motive of the character variety of
representations of the fundamental group of the complement of an arbitrary
torus knot into $SL_4(k)$, for any algebraically closed field $k$ of zero
characteristic. For that purpose, we introduce a stratification of the variety
in terms of the type of a canonical filtration attached to any representation.
This allows us to reduce the computation of the motive to a combinatorial
problem.
