[TPIN] Black stuff in valve port

[Eric Bolvin]

Question here;
Am getting a black buildup in one of the ports of my third valve. The stuff is really hard to get off. I had my repairwoman look at it and she got it off with a chem clean. 
Now a week later, it's back. She said it may be some kind of reaction. 
The horn is a brand new Yamaha Xeno RGSM. I snake the leadpipe and tuning slide daily and the horn is clean but this stuff still shows up. It's like dug into the metal of the valve port. 
I use Holton oil if that info helps anyone.
Any ideas on how to stop this or clean it??

Thanks!!~

Eb

Eric Bolvin
The Really Big Student Songbook
The Arban Manual
www.BolvinMusic.com
www.myspace.com/ericbolvin  
408.236.2009