Le Shuttle, yes. Eurostar no. Nowadays under COSHH regs you can't carry any hazardous materials on a passenger train. Motorcycles are a definite NO.

NO! m bikes of all descriptions are banned in most european countrfies- the nasty little grey suited gauleiters did that long ago( some east Europe may still allow them-depends.
E biks are ok- couldn'y do much about them coiuld they>
but many rails limit num,bers per train. Foldables cant be stopped tho'
And if you can disguise the motor then it may be possible to get6 a moped aboard,i

If its got petrol in it then you aint taking it on a passenger train!