I am also in a similar situation so will add the information I have and also ask a few questions. First I know there are threads dealing with non-resident registration for US plated bikes but am wondering if anyone knows the most current and trouble free options.

Personally, I was planning and am still considering WA. It used to be quite easy to do that. Apparently in the last couple of months they are now requiring a WA license now as part of the registration process. I asked about a Canadian who resides in WA, but wants to keep their Canadian DL, and was told it may be possible with rental agreement, or power bill etc.but it sounds like simple things like mail, or bank statements may not be sufficient. I have also heard this new rule may not always enforced, but would be good to get some info if anyone knows how things may have changed in this regard.

Vermont apparently has tightened their rules now and it is no longer possible. OR is quite similar to WA, except proving residency is easier as you can get a DL, with just a bank statement with your OR address, and an amazon or some other package with your name on it to the same address, and some form of hard ID like passport, birth certificate, etc. South Dakota seems to require a SIN number which is ok for Americans who are not residents of Dakota, but not possible for Canadians and I have found no work around. I have heard Texas is possible, and possibly AZ, and AK, but haven't followed up on the details.

Another thing to consider is whether online registration is possible, whether there are yearly inspections, and whether insurance is required for registration in the case of people using their vehicle outside of US for extended periods. guess Montana LLC is the only one I a currently aware of that seems to be for sure possible. Personally I will try my luck in WA, and if that does not work most likely will go with Montana, but it would be great to hear if anyone knows any other options or solutions...

As far as importing a foreign vehicle into Canada if it is plated in the US, there is a process for doing that and it's fairly straight forward. Anything newer than 2008 must be entered into the RIV system, which is basically a register of vehicles, and that costs $200, US customs clearance (which requires an appointment) is needed before entering the vehicle into Canada, and then duty must be paid to CBSA and provincial authorities. Then you go about trying to register the vehicle which will require further explanation. If the vehicle is older than 2008 it does not need RIV but still needs US customs clearance, and tax and duty paid on entry to Canada.

The obvious issue here is that if the bike is in Europe I imagine it would first need to go back to USA to get customs clearance and doing that without first having attained proper registration would likely be problematic. It is possible by presenting only the paperwork to US customs the clearance could be attained but I am not sure about that.

One other question about a possible simplified cheap solution for the multiple riders who find themselves in this or similar situations. Curious if anyone knows if a Montana LLC could be formed that would operate as an umbrella for multiple owners, each who could have their own vehicle registered in their name, but share the costs of the actual running of the LLC.