Your best bet, for a variety of reasons, is to take a motorcycle safety course. You will learn on their bikes, practice on their bikes, and then take the M1 exit test on their bikes - at the facility you've trained in! This is much better than borrowing a bike here and there and then taking the test on whichever one you can get your hands of on the day of the test.

When I took my M1 exit at the drive test centre about 6 years ago, only 1 motorcyclist passed out of about 10-12 (plus two scooter riders, who both passed). My understanding is that the success rate of candidates who take the test through safety courses is much higher.

If you're already going to be spending some money renting bikes, and eventually buying a bike, you might as well take the course. I believe it can be done at Algonquin over a couple of weekends. Not only will you benefit from what I described above (practicing and taking the test on bikes you're familiar with), but you'll actually LEARN TO RIDE SAFELY AND DEFENSIVELY.