I’ve been working on a 425 magnum. It was running rich flooding out so like many other times on other polaris 4 wheelers i replaced the needle and seat in the carb. Fired it up after a full service and working on the carb. bike runs perfect idling and running until you open it wide open. then it runs lean. Stick a finger over the inlet for the air cleaner and it runs good again. I’ve took off the carb many times trying to find a leak but can’t find out how its running lean. Before replacing the needle it would starting flooding out but run like a scalded ape when you opened it up .