Posted by Paul H on March 25, 1999 at 18:43:07:
Please excuse the length of this post, but I am nearly at my wit's end here.
I have been experiencing intermittent sticky valves problems on my Yamaha YEP-321 euphonium since I bought it a year ago. They never really jamb. They just pause long enough to make me miss the next note. When I "twiddle" the valves, they are always free. I keep it meticulously clean and have tried natural and synthetic oils (being very careful not to mix them).
My local Yamaha repair shop has looked it over more than once and can find nothing wrong with it. The last time it came home after a professional cleaning, it was sticking again after less than two hours of practicing. The shop technician explained that Yamahas are known for their tight clearances. He declined my request to lap the valves in order to open up those clearances a little. As far as he could see, they were perfect and lapping them would seriously degrade the horn.
Any help you may have would be greatly appreciated.