Dice:
Shifting into 1st gear from neutral, when at a standstill always produces a loud clunk. Tis the nature of the beast.
+2.. Even more when clutch cable is not adjusted right...
My opinion is that your cable is too loose... try taking up some slack... But not too much as to make you clutch no be engaged fully whe lever is released...
If not adjusted right, when you pull on the lever fully the clutch is actually partly engaged... making it hard to find neutral and a harsher neutral to first shift...