My first bike aged 5.....well ... my first sit on one. I can't touch the pegs yet though. The bike looks like a BSA X35-0 149cc
but I don't have a photo of a 250 so can't be sure. My Dad was a musician and rode this bike with his saxophone
strapped to his back regularly from Birmingham to Norwich for weekend gigs so I would be surprised if this is a 149cc model.