Inconsistent valve action

[USMCTuba]

I have a mature 822 whose valves stall if I don't press them just perfectly. Of course, the condition creates a crash course in learning to press my valves exactly vertically, but I'd still like to be able to play the next note the couple times in a performance that I don't. The horn is extra clean and I just had them lapped. Do any repair techs out there have any suggestions on how to make the action on these valves more consistient?

[pgym]

Not a repair tech but ... have you checked the valve guides for burrs and cleaned the valve guide grooves?

Also, if the 822 is like Yammy euphs, the valve guides are held in place by the valve stem (it tightens a washer that holds the plastic/metal guide). If the stem has come loose at some time, the guide can shift deeper into the guide slot, which causes it to bottom out and the valve to stick about half way down. No amount of oil or cleaning will help. You need to loosen the stem (you may need to unscrew the stem completely) and reseat the guide in its proper place (there is a little plastic "nipple" that fits into a hole in the valve.) Be careful to seat the plastic guide properly, then push the it in so that the tab that fits into the slot is pushed in as far as possible. Retighten the stem, oil the piston, and reinsert it into the casing.

[SousaSaver]

What you are describing is hard to diagnose without seeing the horn in person.

HOW do your valves hang up? Do they only hang up in the "up" stroke, the "down" stroke or both?

[USMCTuba]

It is consistent, as you say; the cause being indirect pressure on the valve. So long as my motion is strictly vertical they work (1st 3rd and 4th, in particular), but as soon as I press on one side of the button or pull/push in a direction other than down they hang. The inconsistency is really in how I press them. Is there any more possible solutions for our repair tech to try? Have the valves simply been worn in a way that will make them touchy forever?

All that being said, I assure you the issue is not cleanliness. I have scrubbed, snaked and sonic-cleaned the fully disassembled horn twice, snaked all the piping and rinsed twice and specifically scrubbed out the valve assemblies (springs, caps, rubber washers, stems, buttons, pistons, casings) 3+ times in the last three months. This was all prior to surrendering the horn to our repair tech (who inspects every horn with "valve problems" before letting you leave the shop) to have the valves lapped...which of course requires that he clean the valves out again before giving it back. Not to be too bristly, but my instrument is my weapon and when a Marine says his weapon is "clean and ready," then gives it to the Gunny for inspection and only gets the obligatory *hmph* in return, it probably is clean.

Thanks again everyone for any ideas you might have to help us solve this issue!

[Dan Schultz]

I'd be willing to bet there is a problem with the valve guides. Lapping pistons is not a routine way to fix 'sticky' valves on an older horn unless there has been some sort of damage that's caused distortion to the valve body ports. While we're on the subject of distorted valve ports... check the horn over for loose braces. And... see if there is a relationship between how you are holding the horn and the sticking problem.

[imperialbari]

I am very much with bloke on this one.

It may be worthwhile checking for sources reintroducing fabric fibres to the valve casings.

Some types of felt are so loosely structured that fibres will come loose all the time. Go for synthetic felt equivalents.

Cases may be the culprits, especially if the inner lining is worn.

Gig bags also are prone to cause problems because the leadpipe of tubas and euphs tend to rub against the inner lining. My remedy is about folding a tightly woven kitchen cloth around the leadpipe.

And oiling the pistons generously with a thin lubricant like Blue Juice before every playing session also helps the pistons cleaning themselves.

Klaus

[SousaSaver]

I am very much with bloke on this one.

It may be worthwhile checking for sources reintroducing fabric fibres to the valve casings.

Some types of felt are so loosely structured that fibres will come loose all the time. Go for synthetic felt equivalents.

Cases may be the culprits, especially if the inner lining is worn.

Gig bags also are prone to cause problems because the leadpipe of tubas and euphs tend to rub against the inner lining. My remedy is about folding a tightly woven kitchen cloth around the leadpipe.

And oiling the pistons generously with a thin lubricant like Blue Juice before every playing session also helps the pistons cleaning themselves.

Klaus

Klaus makes a great point about fibers. Especially on a Yamaha where the valve tolerances are tighter, smallest amount of filth or fiber could cause you problems.

And as always, I think Bloke is right too. I find the same "problem" with Trombone slides as well. Just when you think everything is clean enough...clean it again.

[iiipopes]

And have the valve casings checked for roundness. My tech says that half of his work on Yamaha valve instruments of all kinds is re-rounding valve casings -- not from abuse or accidental damage, but just because the thin brass doesn't hold true, as well as too-tight tolerances for the common crud we all experience, and which another half- or full-thou of clearance would still be adequately sealed by conventional valve oil.

[Dan Schultz]

Not a repair tech but ... have you checked the valve guides for burrs and cleaned the valve guide grooves?
......

This bears some thought. Aside from the fact that you've already told us that you have a problem pushing your valves down straight... there are two major things that cause 'sticking' on Yamaha valves. The first is that they are just fit too damned tight at the factory. You've already addressed this by lapping them. Now... you've got to put straight-line pressure on the finger buttons. Secondly.... I've found the other major cause for 'sticking' pistons to be poorly maintained valve guides. The problem with Yamaha guides is that they wear fairly rapidly when in the hands of a player who doesn't exhibit good playing characteristics... like not exerting straight-line force of the fingerbuttons.

Valve guides 'slam' back and forth in the guide slot due to the physics of the spring. Depending on which way a spring is wound, the guide will bang one side of the slot on the way down and the other side on the way up. The plastic guide gets worn away on the edges and will hang in the slot due to this twisting action. The corners of the slots that meet the bore really need to stay sharp when using plastic guides. Removing that sharp edge actually takes away from the useful surface of the slot and causes the guides to wear even faster.

It could be dirt in the valve guide slot but it's more likely to be the guides causing the problems. Yamaha has tried to give us what we ask for but I think it's time they offered a harder material for their guides... something more of an engineered plastic instead of the crappy soft stuff (probably just Nylon) that they use now.

[Rick F]

I don't play tuba, nor am I an instrument repair tech (sounds like a motel commercial), but I do play a Yamaha euph (641) which has tight valves. Although my horn is well broken in now at 16 yrs of age, I used to have some problem with sticking valves. I found what was mentioned above helped me. The valve guides can get worn on the edges and form a little burr... especially if you've ever accidentally dropped a valve into the casing when oiling. I've filed off the burr using a small nail file or emery board to correct a sticking valve.

Also, there is a little play in how far in the valve guide's tacquet (part which fits into casing groove) extends into that groove. Not much play — but maybe enough to make a difference in valve action. If you loosen the valve stem (#44 in image below) you can push back the guide (#46-1) some and re-tighten the stem so that the tacquet doesn't protrude into the groove as far. Maybe this will help.

[USMCTuba]

After much exacting inspection and experimentation this morning, I've found the problem seems to be that the aged guides are now too short, and the push (on 4) and pull (on 1) is actually dislocating the tacquet (new term!) from the groove. I loosened the stem and moved the guide forward a little and it worked like a charm...but for how long? What is the best way to go about ordering replacement guides?

[Dan Schultz]

After much exacting inspection and experimentation this morning, I've found the problem seems to be that the aged guides are now too short, and the push (on 4) and pull (on 1) is actually dislocating the tacquet (new term!) from the groove. I loosened the stem and moved the guide forward a little and it worked like a charm...but for how long? What is the best way to go about ordering replacement guides?

AHA!

Send me your snail-mail address and I'll send you a set of new guides... gratis.

[Rick F]

Glad to hear you got it figured out! Kudos to Dan in offering new guides for free.

I'm surprised the tech you took your horn to didn't figure this out himself rather than just lap the valves. I would think that valve guides and/or springs should be the first thing they look at.

[PMeuph]

I'm surprised the tech you took your horn to didn't figure this out himself rather than just lap the valves. I would think that valve guides and/or springs should be the first thing they look at.

Not to mention considerably easier to fix and cheaper.....

[USMCTuba]

Thanks everyone for your input, and thanks to Dan for the new guides!