Had a strange "chuffing" noise while idling. Thought it was a bad vacuum hose and decided to just get rid of all the emissions plumbing. Maybe old news to some folks but a revelation to me, the ports in the engine for the emissions plumbing are 16mm x 2 = Universal auto oilpan drain plug for $1.50
. Had to saw the plug shorter but it is the right thread to get the job done. Probly spent <$5 all together. Not to mention the newly acquired '89R100GS sounds MUCH better and runs smoother-stronger!