OK, not to motorized "stuff" but to motorized bikes - complete idiot. Looking for some basics since I want to get going on a couple for my wife and I. I understand the basics but some help in two areas, please. First, how much space is needed for the motor inside the frame? I see various creative setups but have yet to see any real measurements or specs to help. Seems inportant when picking out the bike to modify. Now the dumb question. Do these use a regular manual clutch for starting the motor, stopping at lights, etc? Or pull start and centrifugal clutch? Or is that a choice I need to make? Thanks in advance! Really enjoy the posts and the insights!