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On the principle that a wild guess is better than nothing, could it be Charlie Chan and the Curse of the Dragon Queen? It was made in the early 1980s, and begins with Charlie Chan — an Asian character, but played on this occasion by a white actor — being persuaded to come out of retirement. Whether the other scenes match I don't know; I don't think I've ever watched it all the way through.

Here's one that's been on my mind for years.
I remember seeing party of a movie on the Mystery channel. It involved a an Asian man convincing an older white man to come out of retirement because he was "the world's greatest detective".
Beyond that, there are only two scenes I remember. First, there was one where the detective was taking a bath and a women walked in on him and screamed.
Second, there was a scene at a fancy party, where he offered to split the money for something straight down the middle, "60-40."
The detective had gray hair and a beard. The movie looked like it could have been made in the 70s or 80s, but I can't be sure.
And help would be appreciated.