Join Date: Nov 2009
Location: Lander, Wyoming
At least the treads aren't STRIPPED and the boss is not Missing Pieces.
They probably dropped the Thick Aluminum Gasket into the dirty oil drain pan and screwed in an aftermarket magnetic drain plug with incompletely cut threads, which 'wedged' the un-supported side of the drain boss open! DANG THEM!!
Grooving the crack with a small rotary file (Dremel Tool) burr and filling/overlapping the area with JB WELD, IS the best option in this case, IMHO.
If it is welded, the welding will burn the sealant out of the center seam. Which can be re-sealed with about 4 inches / 100mm of JB WELD both fore & aft of the drain plug boss.
Otherwise it will Require a Complete engine Tear-down!
Modify at "YOUR OWN RISK"!
Still riding my 1987 KL650-A1. 85,000+ miles & counting