I had the same thing happen this summer. After sitting for one week,my 68 A65 dumped the entire oil tank into the engine sump. Like a fool, I did not check the tank before taking it out for a ride. After a few miles, there was oil everywhere, and the bike smoked like it was spraying for a bug infestation. We drained the sump and refilled the tank. Took it for a test ride, no problems. Two months have passed and I still haven't found anything that would explain it. Everything is fine now. It seems to have been a one-time thing. It seems that these bikes just like to get your attention every now and then.