I dont know what you mean by a "float adjustment ruler", so I don't have one either. if you get the height specs it will be in mm. you can use a wrench of the same measurement and use your imagination on how to use it to measure or cut piece of cardboard or plastic to keep in the tool box. 10 bucks for a set of calipers may be money well spent too.
I am only guessing what you came up with when you say you "set it to my knowledge". If I don't have the specs I set one by adjusting that tab to where you get maximum leverage from the float arms to the needle. That will be the position where the foat arms and the needle are at a perfect right angle. (if you can't understand this go get on a bicycle and see what angle your lower leg is when you can get the most push on the pedal when compared to the pedal arm.) That is the default setting that the carburetor makers send them out at when the unit is for a "generic" or after market sale where no particular model is targeted. for reasons such as angle and even emissions some motorcycle builders ordered them set differently in the past. As you get deeper and deeper into this you will find ways to make float levels work for you to achieve "non OE results".
It is best when you are as far down the list on owners as you to have the engine back to stock or near stock jet sizes after you set the float to factory specs. The reason is that the lost souls who were bandaiding a used bike in it's past a lot of time try to "cure" it by jetting it down. (This kind of tuner is really good at saying things like "all bikes require different jetting, even if they are the same make and model, and have identical parts", and then don't explain any further.) If one of those has worked on your bike before, and you actually do the float fix it may now be dangerously lean. So it is good to know yours is back to stock to start out with. I reset before I do any rejetting.
Now you NEED to find out if it is really shutting off at the point I am referring to: I do this like a million others do, by putting a long piece of fuel line on so i can hold the carburetor upside down and up to eye level. i move the float through it's range as i exhale through the fuel line. Vibration and motion will affect this while the rig is running, but this is where you start, or where I start. It (float level) is about the only part of the carburetor that can have a drastic affect on your jetting at all throttle openings.
Now as your guess on the oil coming from the transmission because it seemed like a heavy viscosity: If you are under 18 I will call that the wrong end of a 50-50. If you are older I will call it short sighted. You could take straight gas and clean out your lower end, upper end, and entire exhaust system. Say you did it with about an ounce of straight fuel. You will end up with some "goo" on a bike the age of yours that is far thicker than anything you are pouring into your transmission I bet. Rule of thumb is to test and not guess.
