I've had several kinds of bikes from a 50cc Piaggio scooter to a 750cc Ducati SuperSport.
Basically, small bikes are for the city only. If you tried to ride a 100-150cc bike in the European summer at max speed (which would be only 80-100kmh anyway) it would quickly overheat. Many of them are not allowed on the interstate or whatever the speed road is called in Europe (autostrada in Italy, autobahn in Germany, etc.)
I imagine you'd have to buy it, register it, insure it, and sell it at a loss in the end. So probably not cheaper than a train, overall.
Basically, small bikes are for the city only. If you tried to ride a 100-150cc bike in the European summer at max speed (which would be only 80-100kmh anyway) it would quickly overheat. Many of them are not allowed on the interstate or whatever the speed road is called in Europe (autostrada in Italy, autobahn in Germany, etc.)
I imagine you'd have to buy it, register it, insure it, and sell it at a loss in the end. So probably not cheaper than a train, overall.