I think the carb is different with the pump than without. Check if you have the right combination. MECOA has K&B now, contact them for advice and info. I just replaced my Perry carb on my old .61 with a K&B carb from an old .40. Had to remove the carb spigot insert to allow the bigger carb to fit. Runs great now! But, I like Perry carbs, and will likely replace the o rings and put it back on just for originalness. Good luck.

V/r, Richard