I have this pump that seems work the way it’s suppose to. But this crack bothers me. 
is there any one who has tried to replace the lever? The manual implies it can be  

This one?  It looks oddly straight, more like an intentional cut.  Looks like both sides.

This is a 'Denki I refurbished, no such cracks or cuts.

Odd to see a crack that way. The force is applied from the other side unless the lever was somehow install to the other side of the camshaft eccentric

18 hours ago, Zed Head said:

This one?  It looks oddly straight, more like an intentional cut.  Looks like both sides.

I think it might be an intentional cut to allow a bend.  Looks like somebody bent the tip to get  more travel.  

It looks like an unfinished project to me. The crack does look like a hacksaw cut but unless that cut was filled with weld the gap would close up eventually. "Seemed like a good idea at the time". We've all had them.