Good read indeed.
I wonder if the author is changing the jets when he changes the oil to fuel ratio? I'm not certain where the threshold would be for fuel/oil ratio to effect a jetting change. Generally, the more oil in the fuel, the leaner the air/fuel mix will be.
Here's a piece of an interesting article that I read. It helps explain the oil/fuel lean condition:
"Enter 2 stroke oil
Okay, now that you think that all that matters is adjusting the fuel to be proportional to the air going into the engine, 2 stroke oil adds another issue that directly affects the air to fuel ratio.
I want you to imagine an empty bucket, with a permanently sealed 1 liter plastic bottle inside filled to the top with fuel. The bucket represents the total air volume possible in a given situation. The sealed bottle inside represents the amount of fuel needed to achieve a good air to fuel ratio (stoichiometric ratio). When we introduce 2 stroke oil, it doesn't affect the air volume, it affects the fuel volume.
You might be asking "why is the fuel bottle sealed"? A sealed bottle has a limit to its capacity. The orifice of the jets are a set size, therefore there's a limit to that jet size's capacity to provide fuel. When you replace a smaller jet with a bigger jet, what's happening is that you're replacing that old sealed bottle with one that is larger. The empty bucket doesn't change.
When you add 2 stroke oil, it goes into that sealed plastic bottle, so naturally since there's only so much liquid that can fit in that bottle, by adding oil some of the fuel has to get dumped to make room for that oil. Therefore, for those who use richer oil to fuel ratios (32:1 is a richer oil to fuel ratio than 50:1), you're displacing more of that fuel with oil. Now in relation to the bucket, you have less fuel to the same amount of air because the oil took some of that fuel away.
>>> !!! PROBLEM !!! Now we have a bottle that has less fuel that we need because some of the fuel got replaced with oil, this is a lean condition, what am I supposed to do? How can I replace the lost fuel and keep the amount of oil I intend on using?
So what can we do?
Let's just say for the sake of this example that 20% of that plastic bottle is oil, the other 80% is fuel. The total ratio requires 100% fuel to achieve stoichiometric ratio. There's no more room for fuel in that bottle, so what we need is a larger bottle that'll allow us to restore that 20% of fuel we lost. Using a larger jet or moving the needle clip down will accomplish this. By using larger jets, you increase the capacity, just like how it would by using a larger bottle. This is why a bike that uses more oil will tend to use larger jets than one that uses a lot less oil.
All things being the same (assuming using the same engine and oil), a bike jetted for 50:1 will definitely be using smaller jets than one using 20:1 oil to fuel ratio. "
