We were just kids. Friend bought a basket case BSA 500 single for $25. All Whitworth, some metrics sorta fit, some standards sorta fit. The rest Crescent always fit. It was stripped for desert play, had the biggest knobby tire on it that either one of us had ever seen, all of 4" of travel in the suspension at either end. Neither one of us had enough lead in or *** to kick it through, until we discovered what that funny little "extra" lever was for on the bars (compression release). You didn't dare get behind it, I swear every time it fired it would chuck a 5" rock at you.