The Government must make an agreement with the EU to allow third parties to transport motorcycles, used for tourism, to and from the EU duty & tax free and agree with the EU that only a letter of authority from the motorcycle owners will be needed to transport motorcycles through the EU border.
You may be interested in these active petitions
The Brexit Trade and Cooperation Agreement does not make provision for the temporary transportation of road registered motorcycles into the EU by third parties for tourism purposes, without attracting tax and duty. Road registered motorcycles that are being transported in this way should not fall into the same generic category as 'freight' and should not be subject to the same regulations as applies to trade movements of exports and imports when passing through UK & EU Customs.