Originally Posted by GearNut
How would you store oil in the line while it is being used as a sight gauge?
If the bottom of the storage line enters the fuel tank at the bottom of the fuel tank you will not be able to get the full amount of stored oil into the fuel tank unless the fuel tank is completely empty. If there is any fuel in the tank when both valves are opened some oil may flow into the tank, but it will stop when the liquid level in the tank and the liquid level on the storage tube reach an equal level to each other, just like what happens when a sight tube is employed to gauge the volume of fuel in the tank.
My 2 cents worth:
You would be better off having your storage tube enter the tank from the top as originally intended, and have a separate tube installed as a sight tube for a fuel gauge.
Connect the sight tube between a fitting attached to the top of the tank and another fitting attached to the bottom of the tank. I would not recommend using a tee fitting attached to a single entrance at the top of the tank to be uses as a dual purpose device for both a sight tube and storage tube entrance as when you open the the storage tube to add oil to the tank some of the oil will most likely enter the sight tube as well and you will play he!! trying to get the gasoline to quickly mix with what does enter the sight tube and spoil your oil ratio in the fuel tank.
Use separate entrances in the top of the tank for each tube.
Yes, I realize that the bottom valve can never be opened until the tank is capable of accepting 96 ounce of fuel. If the tank level is above the hole in the tank, the stored oil will never be able to enter the tank. There will also be an inaccurate mix if 96 oz of fuel cannot be pumped into the tank.
At any given time, the 3/4" clear line would be a sight tube OR oil storage. Like you mentioned, the stored oil MUST be higher than the fuel level in the tank. That will be easy to do. When I normally refill the tank, there are only about 6 ounces remaining of the 96 oz from the previous fillup. The hole in the tank must be above the 6-ounce level/reservoir.
Imagine that the fuel is low and will need a refill in two days. The sight gauge registers zero and the bottom valve is closed. The allen plug is removed, the end valve is opened and 1 oz. of oil is poured in. Then the end valve is closed and the allen plug reinstalled. Two days later, the petcock is closed. As soon as both valves are opened, oil in the clear line flows very quickly into the nearly empty fuel tank. I pedal to the gas station and fill the tank. Both valves are still open, so a small portion of the the fuel/oil mixture enters thru the bottom valve into the clear line.
The clear line now becomes a sight gauge/fuel gauge. The petcock is closed, I pedal for a block to further agitate the mix. Then I stop, open the petcock and start the engine.
The clear line will be an accurate sight gauge until either valve is closed.
The process repeats itself, as the sight gauge level drops to zero. Then the bottom valve is closed and the top valve and allen plug are opened. Oil is added, then the top valve is closed and the allen plug is reinstalled.
The clear line is now to store pure oil, not as a sight gauge.
By the action of the sight gauge, 99+% of the oil in the clear line has been diluted into the fuel mixture. If I tilt the bike rearward or vigorously shake the bike, literally 100% of the measured oil will be in the fuel/oil mix.