our '75 was like that, still smoked even after all the other mentioned items were double checked. Reducing the full load about 3/8ths of a turn finally cleared it up for good. It's an external adjustment on these ones. Good luck.

__________________
H.D.B.
OBK #45
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'75 W115 240D, wife's dd, 197K
........'75 W115 300D, my dd, 245K
.. .. ..........'82 W126 300SD, the 'someday' project