Tiny, that was so it would stay in there long enough to get the filler cap reinstalled! The left side filler cap on my 1942 45 flathead was for the oil tank. There was a dry sump scavenge pump at the bottom of the crankcase that refilled the tank, and lubrication was more or less gravity flow. I'm pretty sure Harley specified 60 weight for that one.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!