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I've got a Miraphone Petrushka F, and the springs just always seems to rattle way too much. It initially bothered me on the original Miraphone springs, so I bought the Teflon coated Yamaha springs, but they're making noise too now. Anyone have any suggestions for a fix? Or a better spring to use?

Coated or uncoated, it is critical that the springs be straight on their own and sitting level in the center of the bottom cap.

Hold the horn with the valves perfectly vertical. Look inside. The bottom of the spring should be centered in the bottom cap and it should not lean appreciably. Then insert the valves without disturbing that position and see how it goes.

If the valves are not sitting straight even though they are centered in the bottom cap, you need to straighten them. Remove the offending springs and place them on a flat surface on their bottom side. If they lean, bend the bottom loop slightly to get them to stand straight. Then turn them upside down and do the same thing. Insert them and the valves as in the paragraph above and see how it goes.

Still not quiet? Remove a noisy spring and apply some slide grease to the bottom loop and the top loop. Put them back in and try again.

Still not quiet? Then I'm out of ideas!

How about Besson-style spring dampers ? contoured rubber-like washers that fit in the valve caps, and centre the springs, to keep them away from the walls.

Like he said, springs have to be in straight. Miraphone springs are designed so that the smaller end goes down into the bottom valve cap and the wider end is what the bottom of the piston rests on. If the Yamaha springs don't fit in the cupped out area of the bottom valve cap, they won't center.