Re: 100:1 Mix
Anytime you reduce the oil content in your fuel mix you have to understand that you are effectively increasing the fuel portion of that mix, or making it richer. The oil is not considered a combustable so therefore when you reduce the ratio you must decrease the fuel to air ratio at the same time.
This is where those who are against 100:1 mixes feel you can do damage to your engine. You must lean out the mix (less fuel to air) to get proper combustion. Reducing jet size is the best way to accomplish this. The naysayers will tell you that leaning that much will cause problems such as overheating, pre-ignition, piston or cylinder wall or bearing damage. What they don't understand is that even with the 100:1 fuel/oil mix, the lubrication is still there. It just doesn't take as much (quantity) as if using standard 2stroke oil.
I don't use jet sizes, 66, 68, etc. I find them too nebulous. I solder and re-drill stock jets until I get a good clean 2 stroke under load and good spark plug color. I've overshot and found my engines running lean at top end. That's when I come back and drill them out one drill size larger, or whatever it requires for best running condition.
With the NT carburetor you can adjust mid range (up to 3/4 throttle) with the 'C' clip and needle but WOT performance requires you to do some experimenting with jet size.
Your altitude above sea level will also have an effect on tuning. The higher you are, the leaner you need to go. The closer to sea level you are the richer you can run the fuel/air mix.
In short: If you plan to run Opti-2, or any oil at 100:1 you'll need to start experimenting with jet size and go leaner with your fuel/air mix for best performance.
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