drain everything, and give it some time to air out, refill the case with fresh oil, and give it a bunch of rotations, work the oil back into the main bearings... then do a fresh oil change again, change the filter, clean the carb, and buy a new petcock with an off setting (they are pretty cheap) it should fire right up and be fine... these old I-4s are pretty bulletproof I had the same thing happen to a 80's KZ550LTD, and at the time it cost me 3 weeks of allowance to fix ($15)