i learned to ride on one of them !!!
my mate were i grew up , his dad had an old triumph bonneville 650 a.c .
a.c. stands for alarm clock , as he used to wake the whole freakin street on his way to work in the mornings
he also used to ride sidecar racing . did the isle of man TT iirc.
anyway , he turned up one day with one in the back of the car for my buddy