There are a couple of items that I take exception to in this thread.
The first is the concept that the Valkyrie had solid valve lifters.
This is not correct. The Valkyrie has no valve lifters at all. Simply a cam, rocker arms and valves.
The second is that valves tend to tighten up rather than loosening up.
This again is incorrect. As the rotating parts wear, clearances increase. The valves do not rotate.
If your Valkyrie is running fine, there is no need to suspect a valve adjustment is needed.
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I take exception to your exception. If the valve face/seat wears faster than the stem, then you loose clearance over time as the valve seats deeper in the head. I've seen it go either way and sometimes vary from engine to engine of the same type, but more often than not you loose clearance over time.
-RP
Absolutamentally correct! Very normal for valves to lose clearance as the valve/seat wears. And, since the faces are at an angle it does not take much wear at all to see a difference.