Assuming you are in the state, your best bet is probably a "third party provider." I have found them to be far more efficient than the MVD offices, plus they should answer your questions over the phone. there is a "service fee" added to the cost of the transaction, but it's worth it to me (something like $20 for a vehicle registration).
If you are out of state... I suspect it will be more difficult.
It would also appear there is some other paperwork you may need to acquire from Customs
And according to HUBB, you should get a letter from the EPA... details: http://www.horizonsunlimited.com/hub...nchorage-51292
There is also the EPA rules: http://www.epa.gov/otaq/imports/canadian.htm
I would also stay out of Maricopa County (where Phoenix is) because they are the only county in the entire country to have emissions testing for motorcycles.