The board was off-line while I tried to figure this out. I drove out the pin and took out the bimetalic spring and decided it was installed with 180? more rotation than it needed. Put some graphite on the shaft and re-installed the spring 180? looser. It seems to be able to open the valve when it is hot now.
I saw a mention of the heat riser on another thread and realized that I hadn't checked the one on my 850Y for awhile. Sure enough, it was sticky and mostly closed. So I lubed it on both sides and worked it back and forth until it was smooth and free from lock to lock and the spring seemed to be working. Cold, the counterweight stayed up. Then took it out to heat it up to see that it was working.
Even hot, the weighed arm remained on the up position which I assume is closed. Everything looks connected and moves freely otherwise. The bimetalic spring on the other side is not corroded. So I wonder if the spring was put under too much tension all along and even when hot keeps the valve closed. I wired the arm down for now and decided I need a little expert help. Drives fine, but it was driving fine even before.
Is there a way to adjust the tension so that it is operating properly? Any other thoughts?
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