Having read reports of problems with trailered vehicles going from the UK to France soon after Brexit I was a bit concerned that the UK might be imposing similar restrictions.
The only real problem I think is that Customs Officers have absolute discretion. If one of them suspects that the vehicle is being permanently imported or is for sale, then they have the power to say "no"
I don't know how we could prove that a bike wasn't being imported for sale if they take that line...but it doesn't seem to be general practice so it's probably just a risk that we'll have to accept.
Presumably you'll have crash helmet and riding gear etc. with you ?