Besson 700 valves
i have a besson 700 euphonium which I have had for at least 25 years it still looks and sounds like new as I look after it but the valves are noisy due to the metal lugs on the valves can these be taken off and replaced with the plastic type which I have seen on sale on e bay etc.
Your euph has the metal screw in guides so cannot be replaced with the plastic Besson ones without some work however I am informed from a reliable source that Wilson plastic screw in valve guides fit the same and are much quieter. You may also like to try a set of the Besson rubber valve dampers for the Sovereign/Prestige euphs. These help to dampen the valve in the casing (obviously!) and do help to reduce some of the valve clanking.