  Fission fragment mass distribution has been measured from the decay of
$^{246}$Bk nucleus populating via two entrance channels with slight difference
in mass asymmetries but belonging on either side of the Businaro Gallone mass
asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb
barrier, at similar excitation energies the width of the fission fragment mass
distribution was found to be drastically different for the $^{14}$N +
$^{232}$Th reaction compared to the $^{11}$B + $^{235}$U reaction. The entrance
channel mass asymmetry was found to affect the fusion process sharply.
