On bi-unitary perfect polynomials over $F_2$

We give all bi-unitary non splitting even perfect polynomials over the prime field of two elements, which are divisible by Mersenne irreducible polynomials raised to special exponents. We also identify all bi-unitary perfect polynomials over the same field, with at most four irreducible factors. We then complete, in this manner, a list given by J.T. B. Beard Jr.