if my 17 year old son passes his car driving test coulld he legally tow an unbraked single axle motor-bike trailer without supervision,
Car licences obtained on or after 1 January 1997
If you passed a car test on or after 1 January 1997 you’re limited to vehicles up to 3.5 tonnes maximum authorised mass towing a trailer up to 750kgs, or a vehicle and trailer combination up to 3.5 tonnes MAM providing the MAM of the trailer doesn’t exceed the unladen mass of the towing vehicle. You will need to pass an additional driving test in B+E if you wish to tow a caravan or trailer combination which exceeds these weight limits.
i think you can, aslong as it doesn’t go over 750kg including the weight of the trailer. i think you can tow the likes of the small trailers you can get from halfords
YES. … and as Hutchie says, providing the combined design weight and actual weight of trailer + load is no more than 750 kgs.
Even though it may be be seen as only a small light trailer, he should still be made aware of the importance of braking only in a straight line, allowing longer than usual braking distance, tyre, light & mudguard compliance, load security & what to do if he gets a wag on. 
(rare with a m/cycle trailer though).
Driveroneuk:
YES. … and as Hutchie says, providing the combined design weight and actual weight of trailer + load is no more than 750 kgs.
.
And the full weight of the car and trailer and load is no more than 3.5 tonnes.
I wouldnt worry about going overweight or over MAM with a motorbike on a trailer. A modern 1000cc sports bike will weigh less than 200kgs.
Conor:
And the full weight of the car and trailer and load is no more than 3.5 tonnes.
4.25 tonnes.
He can also pull trailers with a MAM exceeding 750kgs providing the MAM of vehicle + trailer + load does not exceed 3.5 t and that the MAM of the trailer is less than that of the towing vehicle. Trailers with a MAM over 750 must be braked.
Rog will be along shortly to add more confusion
alfaman:
if my 17 year old son passes his car driving test coulld he legally tow an unbraked single axle motor-bike trailer without supervision,
Do you mean he has a motorcycle licence and wishes to tow it behind a motorbike or do you mean to tow such a trailer behind a car 
If behind a motorbike then I have no knowledge of the licence restrictions for such.
Perhaps others who have such a licence can help.
If not then a call to DVLA on 01792 782 341 may help 
ROG:
alfaman:
if my 17 year old son passes his car driving test coulld he legally tow an unbraked single axle motor-bike trailer without supervision,
Do you mean he has a motorcycle licence and wishes to tow it behind a motorbike or do you mean to tow such a trailer behind a car
If behind a motorbike then I have no knowledge of the licence restrictions for such.
Perhaps others who have such a licence can help.
If not then a call to DVLA on 01792 782 341 may help
Another senior moment Rog ,
If he wanted to tow it behind a motorbike, he wouldn’t need to pass his car test.
He wants to tow a trailer (capable of carrying a motorcycle) behind a car.
redboxer850:
He wants to tow a trailer (capable of carrying a motorcycle) behind a car.
Thanks - I need more coffee this morning…
In that case I cannot expand on what others have already stated 
many thanks for all the replies and advice.
much apprieciated.
regards to all.
ROG:
redboxer850:
He wants to tow a trailer (capable of carrying a motorcycle) behind a car.Thanks - I need more coffee this morning…
In that case I cannot expand on what others have already stated
ROG there are some points in time that i LOVE what you post, this is one of them, put a huuuuge grin on my face 
garnerlives:
ROG there are some points in time that i LOVE what you post, this is one of them, put a huuuuge grin on my face
I only did it to bring you a smile on a Sunday 
Believe that and you’ll believe anything…