Billy,
I think you mean an AJS, a big 500 (498cc) Thumper with a compression release that was needed because the compression was so high. The Tiger Cub was a 200cc Triumph Thumper.
Had both, a 600cc Norton Manxman (Dominator 99 series), 650cc Triumph Bonneville, a 650cc BSA Road Rocket, 750cc Norton Atlas, 850cc Norton Commando, 850cc Norton John Player Special, 500cc Norton Manx DOHC Thumper, 750cc Matchless, 250cc Greeves Griffith, 1000cc Ariel Square 4, a 998cc Vincent Rapide and a 1000cc JAP. They all, except for the Greeves 2 cycle, leaked.
Not to mention the Japanese, German, Swedish and Spanish bikes I also raced later.