I have heard many people complain of the piston valve springs rattling or buzzing against the side of the valve casing. This is usually because the valve is not seated properly in the bottom valve cap.

Whenever you take the valve out it is possible for the spring to no longer be centered in the bottom cap. Usually it will correct itself if you re-insert the valve properly. I try to make sure the valve casing is as vertical as possible. As I insert the valve to the point where it is again contacting the spring (a little before the valve guide touches the top of the casing), I turn the valve in the casing. This helps encourage the spring to find its center again.

If you are hearing noises from the springs (either a buzzing while you play or a scraping sound as the valve goes up and down), look into the hole of the bottom valve cap using a flashlight if necessary. If you see that the spring is not sitting properly, you need to take the valve apart and try again.

If the spring can not be made to behave, try turning it upside down. If that doesn't work, take it out and set it on its end on a level surface. It should sit upright. If it leans, you need to bend the end turn a little until it sits level. Then invert the spring and make sure the other end sits level.