  We study the type II string theories compactified on manifolds of $G_2$
holonomy of the type $({Calabi-Yau 3-fold} \times S^1)/\bz_2$ where $CY_3$
sectors realized by the Gepner models. We construct modular invariant partition
functions for $G_2$ manifold for arbitrary Gepner models of the Calabi-Yau
sector. We note that the conformal blocks contain the tricritical Ising model
and find extra massless states in the twisted sectors of the theory when all
the levels $k_i$ of minimal models in Gepner constructions are even.
