Pretty hard to know what to say here.
You really need to pull the clutch cover off and look into it properly.
The fact that it doesn't go away when you pull the clutch in makes me think it might be the right hand main bearing on the crankshaft, or maybe something to do with the water pump?
As for the noise being worse with the choke on,.. I have no idea at all about that sorry.
It is hard to be much help on this one.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...