Hi Granoturko:

You have received excellent answers (above) from forum members AnTyx, jkrijt, and Erik_G. There's really not much more that can be said unless you specify which country you are interested in purchasing and registering the motorcycle in.

Note that your question addresses two very different and very separate topics: registration (plating) of the motorcycle, and insuring the motorcycle.

The rules regarding registration & plating of the motorcycle are set by the various countries (governments). The matter of whether to insure you (or the vehicle), what the cost would be, and what coverage would be offered is a private sector matter that is up to the insurance companies who operate in the country where you elect to register the motorcycle.

Having said that, I do strongly suspect that no insurance company would offer you coverage unless you hold an EC driver license. This is because the insurance company would have no way of determining what kind of risk you present to them - in other words, what your driving record is - and no way of tracking your future violation history without you holding a local driver license.

I believe that generally (beware, this is a generalization) the Western European countries don't impose too much of a burden on North Americans who already hold a North American license to trade that license in for a European license. It is likely that you will need to pass a written test, and perhaps even take an in-vehicle test, but unlikely you would need to complete all the instructional requirements that apply to a novice driver in an European country.

Be aware, though, that some European countries impose age or experience restrictions on the horsepower of a motorcycle that a driver can operate. I recall that when I was working as an aircraft pilot in Switzerland, a 24 year-old colleague of mine found out that even though his pilot license allowed him to be employed to operate a 70 passenger commuter aircraft, he couldn't ride a high powered sport bike because he was under 25. We used to tease him mercilessly about that...

Also be aware that the relatively easy process to obtain a European country driver license on the strength of a North American driver license favours operation of automobiles, and might not exempt you from ab initio requirements to obtain a motorcycle license.