Ol:
I can't speak for the United States, but I can give you some information for Canada.
Liability insurance is obligatory in Canada. I don't know of any company that underwrites insurance for out-of-country vehicles in Canada, however, I kinda-sorta think that there is some kind of agreement in place between the governments of Canada and the USA to ensure that any automotive insurance sold in either of the two countries is valid for all states and provinces in either country. So, if you have already obtained liability insurance for the USA - or if you are able to obtain liability insurance for the USA - it will 'most probably' include Canadian provinces in the coverage area. But, don't take my word for this, double-check it.
Our Canadian Customs staff are generally pretty friendly, and provided you have a foreign licence plate (and appropriate oval country sticker) on your bike, and all your papers (ownership, registration, insurance) are in order, you should not encounter any difficulty crossing into Canada on the motorcycle - most especially if you enter Canada by road. We don't use or require carnets here. The Customs staff will make their own decision about whether or not they think you will eventually re-export the bike (like a tourist normally would). Their only concern will be that you don't have any plans to leave the bike in Canada - so, make sure you don't say or do anything that would raise any concerns in this respect.
So far as Canadian Immigration is concerned (a different group of people, but they work together with the Customs folks), as long as you hold a passport from an EC country, you won't need a visa. I think you can enter the country for up to 6 months as a tourist. Check the
Canadian Border Services Agency website to find out the exact details.
The immigration folks generally take the measure of you based on the first impression you make, so, it would probably be a good idea to have a shower and a shave the morning you plan to enter the country.
Basically, all immigration is concerned about is that you have sufficient resources to support yourself while you are visiting the country. They don't expect you to show them cash or anything like that - just to look like you are self-supporting, not a refugee.
The last group of border people you might run into are the Agricultural Protection people. Their concern is that you might accidentally and unintentionally import some kind of pest or plague that would harm agriculture here in Canada. So, take the bike to a coin-op car wash and give it a good blast before you cross the border. Get the bugs off the windshield and get any mud on the underside of the fenders cleaned off. Also, don't carry any food (especially meat, fruits, or vegetables) across the border.
I helped a HUBB member from the UK import his motorcycle at Toronto Airport about 5 years ago. The import at the airport went OK (the only thing that the Customs folks were concerned about was whether there was any mud on the motorcycle, in other words, whether or not they would have to call in their friends from Agricultural Protection for a second look). However... less than 5 miles down the road from the airport, my guest got pulled over by a police officer who said "you can't ride a motorcycle with a UK plate in Canada". Fortunately, I was following in my car, and (armed with the experience I have gained in 10 years of riding a Canadian plated motorcycle in Europe), managed to convince the police officer that she was dead wrong, there are treaties in place to permit foreign vehicles to be brought into Canada for a limited time by legitimate tourists.
So, I suggest you plan your border crossing to take place at a fairly major port of entry - don't show up at 3:00 in the morning at the border crossing in Rabbithash, Saskatchewan (population 30), because the government staff there might never have seen a vehicle with anything other than Canadian or US licence plates.
Be aware that a helmet is obligatory in all Canadian provinces. In theory, it has to have a North American (DOT) approval, but in practice, as long as it looks like a run of the mill motorcycle helmet, no-one will raise any concerns about that. I am pretty sure that the inspections for DOT approvals of helmets are only carried out on bulk importations of new helmets intended for resale, not on helmets actually being worn by riders.
Lastly, be aware that radar detectors are illegal in most Canadian provinces. Mere possession of a radar detector is illegal, which means you can't just stuff it in your pannier.
Hope this helps,
Michael