These make me feel both ancient and nostalgic at the same time Tas!
Coming from a family of 'Scrambles' and 'Motocross' racers I well remember the period of four-strokes being replaced by two-strokes, as my Father raced Velocettes when we were kids and both my brothers went into the Scrambles/Motocross arena during the mid 1960s.
I was the odd man out, four wheels were my thing.
Aside from the Velocettes we had an assortment of Tribsa and Rickman machinery cluttering up garage space, soon supplanted by various models from Greeves, D.O.T, Bultaco, Cotton, CZ, Montessa and Yamaha.
My youngest brother even attempted a (very) brief foray in 'dirt mania', at 'Tracy's Speedway' one Summer, not a rewarding experience at all.
Ed did win an Australian 125 Motocross Championship and numerous other 'A; grade titles, Rob remained in 'B' grade and thus avoided injury.!
They both rode a few tarmac events at Winton, Calder and Sandown, 'just for fun'.
Marriage and kids eventually removed them from competition, probably a good outcome for both, or rather, inevitable.
Today I own several 'Sports Bikes' that I run at the odd Track Day, which my surviving sibling regards as not very bright.
I'm a late bloomer I guess.
Love the images.
John L aka Biggles_101