This paper describes the beam transmission characteristics through the spiral inflector and in the central region of the K500 superconducting cyclotron at VECC due to solenoid magnet misalignment in its vertical injection line. The equations of motion for a particle in misaligned solenoidal channel are derived from the Hamiltonian and used to investigate the behaviour of the beam during injection where the axial magnetic field of the cyclotron plays an important role. We have optimised the solenoid strength in the vertical line to reduce transmission loss in the spiral inflector and to match the beam in the central region of the cyclotron. The percentage of the accepted particle in the spiral inflector and in the central region are calculated for different values of translational and rotational misaligned parameters of the solenoids. The allowed tolerances of these parameters are obtained to get the desired injection efficiency.