What I have is a 1978 Sportster I replaced the Clutch "side gasket".
After getting it back together and adjusting the clutch, I inherited a sporatic "POP" while pulling-in the clutch lever.
It seems to happen just before the clutch lever is completely pulled-in. And it does not do it every time.
It might be the release mechanism. If it persists you might drain the primary/tranny pull the cover and check it out.
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