I have the Yamaha video that shows how to change the oil and the one included here that shows how to check. Great explanations.
And now a question that I've never seen asked or answered: What happens if someone puts more oil in than necessary -- enough cover the dipstick as 'full'? What effect does all of that extra oil have?
It will come out through your crankcase breather. And since it looks like you have a stock air breather, that means it will come out there. there have been cases where it started dripping from the bottom of the air filter.
It can also get sucked into the carb