Keep in mind that the Canadian Customs staff (the border guards) really have no interest at all in who owns the motorcycle. Their only interest - if any - would be to ensure that you do not intend to leave the motorcycle behind in Canada, or sell it in Canada.
Canadian police - who you may or may not encounter during the course of driving around - may have a very slight interest in the fact that the registered owner of the motorcycle (as evidenced by the registration papers and the insurance papers) is not the same as the driver (as evidenced by your driver licence and/or passport), but as long as the motorcycle is not listed as being stolen - something that the police can easily check in this computer day and age - chances are that they really won't care who owns it either. The police will want to see documents that prove that the motorcycle is properly registered, has a current licence plate, and has current insurance.
Insurance papers in Canada and the United States all follow a common format, therefore, if the bike is correctly insured in the United States and you have proof of insurance, then it will be correctly insured for Canada as well.
Vehicle insurance (liability insurance, in case you cause harm to someone or something else) is obligatory in all Canadian provinces. There are very strong penalties if you do not have liability insurance. Collision insurance (insurance that will pay to repair your moto if you damage it) is entirely optional. As Bobkat suggested, it is a very good idea that you get what is called "uninsured motorist" coverage, in case you are involved in an accident with someone who (in contravention of the law) is not insured.
Bobkat's suggestion that you get a notarized letter indicating that you have the permission of the owner to be riding the moto and - more specifically, to ride it in Canada (to cross the border) - is a good one. I ride my Canadian registered motorcycle in Europe, and because it is registered in my wife's name, I carry a notarized letter indicating that I have her permission to be riding this Canadian registered motorcycle all over Europe. I have, on one occasion, had to show this letter to a policemen to assure him that I did not steal the motorcycle from my wife while she was sleeping.