Yep-642 valve issues

[Primusbot05]

Hey gang, just curious to know if anyone out there has any suggestions about how to avoid the very attractive greenish-brown smudge that builds along my valves. I took it to get cleaned again today and the dude said that was what was catching, not my valve guides. Any suggestions? Change of diet? Stop playing? Throw it in a river and call it a day?

[Teubonium]

I used to get this when I used Hetman's Synthetic valve oil. Since I've been using Blue Juice, no greenish slime build-up!

[tokuno]

I used to get this when I used Hetman's Synthetic valve oil. Since I've been using Blue Juice, no greenish slime build-up!

Hetman's seems to stain my clothes less than 'real' oils (no spit catcher on my horns).
Haven't experimented with different oils to see if it affects the rate of slime buildup, but I seem to recall getting it regardless of the oil. I run a tubasaver through the valves and leadpipe every now and again and brush off the valve guides. Doesn't take much time and seems to keep all the moving parts working as expected.

[joh_tuba]

The chemistry of the yamaha monel valves has changed more than once over the years. Some corrode more quickly than others.. some are 'ok'... others seem to need constant attention. I've seen one particularly bad off Yamaha tuba that would move smoothly until played then become unplayable within minutes of exposure to moisture. In my opinion, a GOOD high quality nickel plated valve(cheap plating flakes off) always moves more smoothly than the best monel valves. Monel was a cost cutting measure by Bach(starting with their trumpets) that turned into an advertising gimmick. I suspect your only real solution is going to be to get a different YEP-642 or order replacement valves. In the mean time.. live with it. :/

[Rick F]

I used to use Hetman's (light) on my YEP-641S — also with monel valves — but switched about 2 yrs ago to Yamaha Synthetic Light (LVO). I never had any issue of stains forming on the valves with Hetman's. Hetman's did leave a yellow residue in the valve ports and bottom valve caps which is why I switched. I do clean the valves and valve casing periodically with HW Brass Saver brushes and warm-soapy water.

[SousaSaver]

It is brass oxide (from the brass valve casings) that bonds over to the monel pistons.

If you oil the valves more often (relying less on condensation to lubricate the valves) this will occur less.

Exactly right.

[IOS]

This is a common problem and easy to deal with. Periodically clean off the brass (copper) oxide with a solution of muriatic acid - four parts water and one part muriatic acid. Lowes and Home Depot both carry muriatic acid (about $5.95 per gallon). When mixing the solution, be sure to add the acid to the water not the other way around. Put just the valve in the solution for about ten seconds. Next, put the valve in a baking soda solution to neutralize the acid. Wash the valve and wipe it down. If the valve is badly corroded, repeat the process. When doing this, be sure to wear rubber gloves and eye protection since you are dealing with an acid. (Remember all those safety precaution from your chemistry classes.)

[Teubonium]

... When mixing the solution, be sure to add the acid to the water not the other way around. ... (Remember all those safety precaution from your chemistry classes.)

As my eighth grade science teacher taught us:

"Here lies Johnny cold and placid,
he poured water into acid!"