Posted by Matt Walters on April 07, 2002 at 20:34:32:
In Reply to: Venting Rotary Valves posted by Justin Beish on April 07, 2002 at 15:31:48:
Just logged on for the weekend and saw your question. Since the rotor has to be removed todo this job, and the inisde of the casing has to be deburred, AND then the shavings a grit washed out of the horn, I recommend it be done as part of a full chemical clean and servicing. That way you are not paing extra to have the horn cleaned out, then cleaned out again at a later date.
1) REMOVE the rotor
2) CREATE a centering hole for the dril bit. I often use a long, sharpened rod with a gound point. I'll hold it where I want it and have someone else hit the punch for me.
2a) I now prefer to put the hole higher than centered. That gives a broader area for the rotor to seal the hole. Not important on really tight valves, but old leaky ones appreciate it. So now, it's my habit.
3) DRILL the smallest whole using a long Aircraft Drill bit.
4) DEBURR the inside of the casing. The goal would be to create a small countersink on the inside of the casing at the drill hole.
5) CLEAN out the horn.
6) WASH out the horn! Stuff manages to go places it should not have. Don't forget to wash out the slide tubing!
Put your horn back together with fresh oil, etc.
The actual drilling and deburring is about 30 minutes work. It's the extra stuff that s normally done in a cleaning that would cost you a lot more.