observations

[iiipopes]

I think the word bloke is looking for is "anecdotal."

[Worth]

Those who say that their Wisemann pistons (i.e. normal application: in their Wisemann tuba) don't feel as "smooth" as B&S/M-W pistons possibly (??) are simply feeling the (c. .0005 - .001") closer tolerances of the Wisemann pistons, which (also) require (even) more (than B&S/M-W) cleanliness and (possibly) a bit of aftermarket gentle hand-fitting.

Although I have a whopping sample size of 1, the above statement confirms the close tolerances I've observed and dealt with on my 900. After ongoing issues with valve #1, I bought some fine grade lapping compound and hand worked this valve to a point where the compression is unaffected and the valve is smooth and trouble free. Just last night valve 3 was wanting to hang slightly and oiling was not addressing the issue. Removed the valve, spring, and bottom cap and ran a rag through the casing, reassembled, oiled, and voila smooth action restored. Have had this horn close to a year with no bath or QHR yet to remove manufacturing debris or possibly residual debris from the first valve lapping. May be time for that!