There really isn't a single company that is cheapest for everyone. You'll hav eto shop around...and I can pretty much gurantee you that Kingsway and Primmum WON'T give you the best rate.
I was with Kingsway three years ago....then my rate went up 40% for nothing. I was going to quit street riding, then I lucked out and got insured through State Farm. A buddy of mine knew an agent who got me insured with just a bike (great because I don't own a car).
Then the broker sold all his bike contracts to another company called Nordic Insurance (or Nordique?). I still deal with the same guy and the price is still the same, so no big deal. I'm now 26 and paying around $1200/yr for liability coverage on my '02 750.
M2 license, clean record except for one minor ticket 2.5 years ago (65 in a 50).