The last ones I got from CB750Supply were not Keyster, and worked decently. You might ask them what they have today. The "Made in Japan" ones we were getting last year came from the Daiichi region of Japan, which s where that tsunami wiped out so many things for a while.
Usually, the old ones can be sufficiently cleaned to work well, because the leaks they have are caused more often by the grit on the sides and edges of the valve making the valve drag and stick. I clean them with a razor blade (gently!) and I think I have only replaced 2 valves in the last 5 years or so, cleaning many sets of carbs in the process.
