i would not put the cotter in backwards .
the kick shaft has (..had ) an angled flat and the cotter has an angled flat .
they are designed to go in 'only one way' for the wedges to properly fit .
the kick start quadrant and spring are pre-loaded , by winding the shaft ,
before placing on the inter-cover
... but then its ...
the inner cover that has the stop that controls the kick levers top/stop position
(part 4) ... once the outer cover is wiggled into place .
the stop could be missing
... the parts , or parts fit , are worn by time
... or the quadrants- stop is out of spec ... or was never that tightly held .
if you want to fiddle with the stop angle ... adding some braze to the quadrants stop-radius
might be the simplest approach ?