Xmas of 1995 (5yrs old), got a 5hp go-cart. Then upgraded to a KX85 few yrs later, then Tri-z 250.
I started riding when I was 11 or 12 with a 50cc 2 stroke moped, but in no way was it fast enough.
After porting, and building the crankshaft up with epoxy (rotten stuff called "Plastibond" which took ages to cure) I all but doubled its speed.
I was no stranger to 2 strokes, before the 50cc moped, I am sure I had the fastest Atco barrel mower in the country, you had to sprint to keep up to it.