Most of my friends stayed in school long enough to have a class called "Gee, I'm a tree" Working, I have had to learn a little. If I need a 6 by 8 space to have square corners I would tape the diagonal at 10 ft.
A test? Grab a tape measure, a string, couple of spikes, and a small bag flour, ride the MC to a level area. Stake one end of the string down, and pull it straight. Now poke a small hole in bag, and draw a line on that string. Measure 8 feet on the line from where you pinned end of string, pin the end of tape. Now, pull out tape, and use the flour to draw a arc at 10 ft mark. And while at it, draw a arc at the 6 ft mark to start to locate the 4th corner. Move the dumb end of tape to the first pin. Where the 6 foot mark lines up with first arc, that is corner 3. 10 ft and other arc, corner 4. Use the flour to draw the other 3 sides, roll the bike in, check for fit.
More I think, might be better to do at home, using masking tape on garage floor, and one of the garage door posts as starting pin. Then you will know how close to the side of door you can start, how far in you can be and still turn to get front wheel where it needs to be. Can you slide the back of bike sideways at least the width of machine when loading/unloading?