Pianotech

CLR?  I used to use chromic acid, with a bicarbonate buffer.  I found a formula that was used to clean tubas and other brass instruments, and I had to go to a local chemical dealer to get this stuff.  I doubt I could buy it anymore.  It's not dangerous, but you mix it with water.  It's a very deep purple-ish color.  Get it on your hands and it will stain.  If you leave something brass in it for some time, it will dissolve.  But not like sulphuric acid, it won't burn.  I used this for some wheels, exactly as you have there.  Completely removed all the corrosion.  I also used it to clean off the long hinge on a piano, using a large plastic pipe capped on one end.  Maybe you can find this stuff somewhere.  I'd have to dig up the formula, but it was like 20 years ago, so don't hold your breath.  Good luck.

Wim,

Pardon my reply to your post. I'm a stickler about nomenclature. Yamaha casters (U1) don't employ bearings -- they use pin and bushings. There is a difference and could have a bearing (pardon the pun) on how to treat the problem. Bearings, both roller and ball would definitely be destroyed with harsh chemicals such as muriatic acid, whereas pins and bushings used in those casters could survive the chemical if not left in the acid too long. Also, one needs to use rubber gloves and thoroughly rinse the product with water after emersion. 

Just order new ones from Yamaha along with screws and whatever items like sockets/plates/bushings. Beware that current production may be different and not an exact fit and may require some woodworking. I recently had to do replacement casters on a G2 grand- old ones totally seized and discolored with verdigris, rust  due to pet urine. I would not mess around with chemicals , polishes or home brews. Chemical burns, fumes , water and acid reactions, splashes,fumes are bad for you.

Wim,

Pardon my reply to your post. I'm a stickler about nomenclature. Yamaha casters (U1) don't employ bearings -- they use pin and bushings. There is a difference and could have a bearing (pardon the pun) on how to treat the problem. Bearings, both roller and ball would definitely be destroyed with harsh chemicals such as muriatic acid, whereas pins and bushings used in those casters could survive the chemical if not left in the acid too long. Also, one needs to use rubber gloves and thoroughly rinse the product with water after emersion. 

James,

You have almost zero chance of getting replacement casters for a Yamaha of that age. In fact you likely need to wait months for those casters for current U1's. There are times when we as technicians need to deal with the reality that we must repair, to the best of our ability, those issues where the replacement option is impractical or impossible.

Just order new ones from Yamaha along with screws and whatever items like sockets/plates/bushings. Beware that current production may be different and not an exact fit and may require some woodworking. I recently had to do replacement casters on a G2 grand- old ones totally seized and discolored with verdigris, rust  due to pet urine. I would not mess around with chemicals , polishes or home brews. Chemical burns, fumes , water and acid reactions, splashes,fumes are bad for you.

Wim,

Pardon my reply to your post. I'm a stickler about nomenclature. Yamaha casters (U1) don't employ bearings -- they use pin and bushings. There is a difference and could have a bearing (pardon the pun) on how to treat the problem. Bearings, both roller and ball would definitely be destroyed with harsh chemicals such as muriatic acid, whereas pins and bushings used in those casters could survive the chemical if not left in the acid too long. Also, one needs to use rubber gloves and thoroughly rinse the product with water after emersion. 

I have been there and tried the repairs to the seized casters trying all sorts of things including rust busters, ammonia, wire brushes, wire wheels, brasso . They where so bad it was as if they where welded. Because of the supply chain fiasco it took 15 weeks to get new G2 casters. two arrived and the third came 2 weeks later. Went to install them and found out they where oversized for the hole. required making a template/jig and routing out a slightly larger mortise. The same piano required a completely new lyre including new petals. The brass pedals had green verdigris all over that would not come off. In addition the pedal box felt and wood had been thoroughly soaked by urine and even after a month outside on a protected porch it smelled. Yamaha searched their stock rooms and found the exact lyre in the same finish. It was a short height that bolted to a mounting block . The piano was 1980's vintage so 40 + yrs old. Another yamaha upright had the right pedal horn snapped off. Yamaha had a complete set of 3 exact finish and shape and that piano was 1970's. 

Sometimes we get lucky 

James,

You have almost zero chance of getting replacement casters for a Yamaha of that age. In fact you likely need to wait months for those casters for current U1's. There are times when we as technicians need to deal with the reality that we must repair, to the best of our ability, those issues where the replacement option is impractical or impossible.

Just order new ones from Yamaha along with screws and whatever items like sockets/plates/bushings. Beware that current production may be different and not an exact fit and may require some woodworking. I recently had to do replacement casters on a G2 grand- old ones totally seized and discolored with verdigris, rust  due to pet urine. I would not mess around with chemicals , polishes or home brews. Chemical burns, fumes , water and acid reactions, splashes,fumes are bad for you.

Wim,

Pardon my reply to your post. I'm a stickler about nomenclature. Yamaha casters (U1) don't employ bearings -- they use pin and bushings. There is a difference and could have a bearing (pardon the pun) on how to treat the problem. Bearings, both roller and ball would definitely be destroyed with harsh chemicals such as muriatic acid, whereas pins and bushings used in those casters could survive the chemical if not left in the acid too long. Also, one needs to use rubber gloves and thoroughly rinse the product with water after emersion.