Nice ride!!!
Its probably, timing, accelerator pump or choke. Carb looks new but you never know could be bowl isint staying full, a float needle/seat issue, fuel pump has too much psi etc.......
Valve sticking? just pull off the rocker arm and see if the tip is siting the same as the one next to it, maybe a seat issue.
If you think 'it' is not sitting right, is that the valve tip, pushrod into the rocker arm cup or???
You can do a top end rebuild, its not a waste, just do it right. But if it runs ok, doesnt make bad metal sounds after the accel issue is fixed i wouldnt waste the time, If it runs, drive it!
ALWAYS think simple things first!
WELCOME!!!!