1hz knock can’t figure out

[Ezecool]

Ahoy hoy fellow cruiser matees got a 1hz which has a knock knock doesn’t start till about 10 seconds after start up dulls right down once warm but is still there Beb have been changed any ideas ??

 

[Bmonck]

Maybe post a recording?

 

[Ezecool]

Pulled the fuel injectors 5 are black with soot one is clean what could this mean ??