Okay, first off, what vehicle/engine are we talking about?
FL250?
FL350?
Pilot?
You realize that these are TWO STROKE engines - you DO NOT add oil to the bottom end of the engine like you do a FOUR Stroke.
They do use regular motor oil for other parts of the engine and have fill/drain areas for them, but as far as the crank/piston assembly, it's not something you pour oil into the engine to lubricate.
That lubrication is through oil that you add to the gasoline - premix.
You must mix your gas with a QUALITY grade two stroke oil - most people prefer Spectro, Yamalube R, Honda's two stroke oil, Maxima, Klotz - BRAND NAMES and NOT crap you get a Wally World or K-Mart.
Mix the oil at a ratio of 32:1 This means 32 parts of gasoline to one part of oil. Simplest way to achieve this is to add 16 ounces of oil to 4 gallons of fuel. You can also run 40:1 by adding 16 oz oil to 5 gallons fuel.
A normally running two stroke engine will produce a small amount of crud on the top of the piston - it's alright.
Give us a bit more info and we'll get you going.