I always thought the main problem was that synthetics are too thin. Don't have to be I suppose and if I could get a 20/50 synthetic I can't think of a reason not to use. I wouldn't mind........better off with tractor oil from my local shop. Many years ago when money was tight I woulod drain it out of my Beemer and put into our 2CV.
If a bike needs synthetic how do you travel in out of the way places ? KTM anybody ?
Richard