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Having a horn on trial pretty much limits your options, but since I see that you're in NYC, probably the best thing you can do is take it to Matt at Dillon Music. He'll definitely be able to help. In the meanwhile, I would go ahead and drop some lube down the corresponding slides and see if that helps.

Please forgive my stating the obvious, but has everything been properly cleaned and re-lubricated: the top spindle bearings soaked and the well in the bottom caps filled with sewing machine oil; and the linkage cleaned and lubed with something like 3-N-1 oil? (These are not my recommendations, I got them from Roger Lewis) Then a little piston valve oil directly onto the rotor to make sure any gunk has been washed out from between the rotor and the casing?

Every so often my 186 rotors gets sluggish, and I have to remind myself to go through the entire regimen, and it clears right up, still on its original rotors, bearings, spindles, "S" arms, swaged bearings, and paddles after 40 years, most of those in the form of hard use/neglect/abuse as a college horn before I got it.

I'm assuming that you do know how to properly dsimantle and reassemble rotary valves.

With the linkage disconnected from the stop arm, check that the linkage moves freely, also check that the linkage to the stop arm has not been over tightened and that all moving parts are properly lubricated. Then see how well the rotor moves with the linkage disconnected then with the stop arm off, allowing full rotation.
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The biggest enemy of rotary valves is "dirt"of any kind. This could include any lime build up and possible lapping compound from the valve work previously done. It could be a good idea, and inexpensive one, to pull the valves out and make sure they and the casing are abolutely clean. Also check for any signs of wear on the rotor and spindles and the bores of the bearing shafts. This may appear as either rough, scratched or especiall shiny spots.

As you reassemble them, first oil the bearing which goes into the removable bearing plate and see if it will spin freely on the rotor with it seating fully unto the shaft- if it doesn't it is most likely too tight or damaged.

Next oil the fixed bearing and the rotor and see if the rotor will spin freely all the way until it is seated completely into the casing without replacing the removable bearing. If there is any binding or sluggishness the valves may need lapping or the bearing might be misalligned with the latter being a more expensive repair - possibly meaning having the job redone.

If all is well to this point replace the removable bearing plate, using gentle taps working right around to ensure you drive it home square to the bearing shaft. Even a very slight out of square alignment will cause trouble. Some might disagree but, I like to drive the plate home until it is too tight - slowing or locking the rotor then very gently tap the valve from the opposite side until it runs freely. Sticking during this operation COULD indicate that the hole for the shaft on the removable plate and/or the opposite end is out of square and /or off centre to each other and/or the rotor/casing. If this is the case, lapping (if it is very slight) or a valve overhaul are probably going to be required.

Make sure the valve still runs freely with the stop arm in place then with the linkage attached. It is even possible that a change in the position of the spatulas, will make a difference.

Again, assuming you know what you are doing, this operation might well fix the problem at absolutely minimal cost or at the least give you some clues to pass on to your tech. If repair is required you might want to consider this cost in determining what price you are willing to pay for the horn.

As said previously the quality of valve overhauls can vary greatly.

Should you conclude that lapping the valves will do the job use a hand drill and wrap the shaft with something to prevent scarring it. Brasso makes a pretty good low cost lapping compound for jobs not requiring too much lapping. Using any lapping compound means a very thorough clean up will be needed.

While you are doing this whole job you will be able to check valve alignment and adjust/replace bumpers as required.

CAUTION........ the seller could try saying you are to blame for "damage" should you do anything - even if it improves the situation. Possibly wise to check with the seller first.

Personally I would not try anything on a tuba just on trial. If you are dissatisfied with the valves, just pass this one over unless it is a unique model you are willing to put in money to get professionally in order (once purchased).

Neptune has amplified my provisos;
one, my assumption that you know what you are doing with at least the basics of servicing rotary valves and,
two that you either take a risk or get permission.

If it is that sweet 184CC at the right price well, (or maybe some real "find") then you consider all options. Not being there I can only offer advice with the main point being proceed with caution.

If the total price of the tuba + possible repair costs is still a good deal, I say keep it. Rotary valves are rotary valves, and can certainly be fixed, if worth the time and money. If it's not a great deal to begin with, pass.

Actually, try a little experiment. If the horn has had a regular diet of Hetmans, there is a gunky yellowish build-up that can occur over time. Where you would normally use the Hetmans Bearing oil, put a couple of drops of Al Cass in those places. Then, without pushing the valve down, pull each slide to create a vacuum to draw the Al Cass down into the bearings. Do this several time with each valve and I believe that it will help dissolve the Hetman build-up a bit and make the valve work more properly.

This is not a slam against Hetmans, but it does have a tendency to build up on the bearing surfaces without regular cleaning and this just helps you avoid having to dismantle the valves to see how it plays.

Just a thought. All the best to you Ben.

Roger

The professional advice when I visited the B&S factory was to only put oil down the slides into the valves if either they are sticking/slowing, or the tuba is going to be unused for a period of time (more than one week). The normal moistness from playing should be sufficient and putting oil inside is likely to hasten the build up of dirt. There is no specific oil for inside rotary valves, but use piston valve oil.

I have followed the B&S advice this last 6 months and had no valve problems.

My guess is that the problem with your new PT-20 was simply that the valves were dry inside after sitting unused in the shop.