First, I just started playing the game today. So much potential. But turning speed is absolutely killing me right now. The radius is comically huge. Is there a way I can change it?
You can't change the motorcycle, it's hard-coded. HV's turning is affected by thruster placement and RCS use. The further forward or back on the HV the side thrusters are from the ship's center of mass, the higher it's turning speed will be. It's the same with turning in any other direction and thruster placement on the same axis. This applies to all ship types. Any decent earlygame HV/SV will have no RCS at all and turn solely on thruster placement.