how to check a float

Never had a NP float fail. There is a way to test them. There is a weight test, 7.5 - 8gms.
Another method which I like better: the front end of the float has a section cut out. Sit float on a flat surface with this pointing up. Gently push down on metal end with your finger & then remove your finger. If float is good it will stay up in the air.