Faulty Vintage Rotors
The Lehnert Centennial Eb Bass: It works - to a degree. The sound quality is quite good, and responsive.
But the valves . . . they are a problem. They will work for a while, but then they will stick - I suppose bind is more correct.

Sometimes up and sometimes down.

They are of the old mid 1800s style. My guess is that there is too much play in the stop arm on the shaft, or there is too much play in the bearing surface.

Before I tinker with this further, I thought I would ask you folks if you had any insight into 1) what the most likely problem might be and 2) whether you have any good techniques to fix the problems. I don't really want to be any more aggressive with those valves than I need to, but I do want them to work.

Reply #1 - Nov 4th, 2007,

Not that it means anything, but the caps look like my Centennials (although one IS just a valve section...)

If the shafts looked anything like the skin, you might want to try some non-abrasive cleaner like Tarni-Shield to remove the crud, but none of the metal.

And how are the springs? Steel kept like that often loses its tension. You may want to try some newer tuba rotary springs if it has.

If you haven't replaced the stop corks, the valves may be travelling ever so far than they're used to. Again, something like Tarni-Shield may work in the casing walls if they're hanging up there.

Reply #2 - Nov 4th, 2007, at 2:14pm

The body of the rotor is not supposed to touch the housing. Try to apply a very thin layer of blue marker color on the rotor body, and insert it carefully, so that you do not get in touch with the housing. Let the valve work a little and see if blue marker has set off to the housing. If it hasn't, we can eliminate that problem.I also suggest that you have a look at the corks. It could look as if some of the cork ends are too wedge-shaped and may get caught under the head of the stop arm.

Reply #3 - Nov 5th, 2007, at 12:51pm
Do you get the binding/sticking with the strings off? I have had strings that were designed to be strung backwards. If I strung them what I think is normal (Conn French Horn) they would tend to stick.