Had a customer 1660 do this several years ago. Turned out a baffle broke loose in the oil pan and got over the suction pipe every now and then. Had to raise the engine.
Thanks for the advice. Did worked for me. I have raised the engine, took off the oil pan and baffle broke loose on my machine also (the one on fan side). Hard to belive, but true. I will try to weld it better tomorrow, and put everything back together. Only gasket is a (small) problem, but will work something out. Thanks again.
