1982 XS650 Heritage Special - Decel popping on one cylinder

[fenbrancis]

If the air isn't leaking past a valve, the valve sealing (lack thereof) is not the source of the "popping"

If I’m reading you right: when you do leak down test on cylinder at TDC compression stroke and you had a leaky valve it would not be seated and could cause the popping.

 

[jpdevol]

Yes