Re: Problem with F822 pistons

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Posted by Kelly O'Bryant on January 23, 2000 at 12:24:10:

In Reply to: Problem with F822 pistons posted by Costantino Volpe on January 23, 2000 at 05:14:07:

You might want to consider having your valves lapped, in addition to the
other good ideas by the folks below.

I think it is typical of Yamaha tubas/euphs to have very "tight" valves.
All of my students who own Yamaha tubas/euphs have had their valves lapped,
and the result is MUCH better valve action.

I owned an 822 F for a while, before making the decision to return the 621 F,
albeit considerably modified now. On both the 822 and the 621, the valves were
extremely tight with incredibly close tolerance when I first got the horns.
After lapping them, there was considerable improvement.

You can purchase lapping compound yourself. It comes in different grades of
abrasiveness. If you do it yourself, be careful. Remember, you are actually
stripping away a tiny layer of the piston. Too much, and you could be in

I've lapped my 621 F a few times, in order to get "Bach Trumpet" valves. I
can tell you from my own time spent doing it that lapping is an extremely
messy, tiring, and sometimes frustrating experience. It can also be quite
time consuming. And, sometimes you will lap your valves, clean the whole horn
out and re-assemble it, only to find out that you aren't done. It can be a
very "trial and error" thing until you find the level of valve action you are
looking for.

It is EXTREMELY important that you thoroughly clean your horn out after lapping
your valves. And, small amounts of the compound residue will linger in your
horn for a while, thus continuing the lapping process on a very small level.
For the first few weeks after lapping, you need to be sure that you clean
your horn out on a regular basis.

It's a lot easier to pay Matt Walters (hi Matt!) to spend an afternoon doing
this for you, but he knows all too well that it is messy, tiring, and time
consuming. And, I made the mistake of having him teach me how to do it, so
when ever I want to have something lapped, he hands me a jar of compound and an
apron and points me to a workbench...

Hope this helps.

Kelly O.

Kelly O'Bryant
Annapolis, Maryland

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