MicroSquirt.com read only forum (Jan.15,2018)

That is the other problem with O2 sensors and two strokes. The sensor doesn't measure concentration directly but indirectly by partial pressure so if there are any (oil) vapors in exhaust gas, it will read richer than it should.

Then how come mazda rotaries can run with an O2 sensor as they have oil injection ??

Because mazda rotary doesn't run a 40:1 gas-oil ratio, but closer to 2000:1. :RTFM: Read the Innovate LM1 recomendations, you'll see. I suppose a narowband O2 sensor might last for a while. The question would be ...

Well, for one you cannot use O2 sensor to tune, oil in exhaust destroys the sensing element within seconds. You will have to use EGT sensor and tune by exhaust temps. Are you thinking about using premix or separate oiling injection (some two strokes do that). It would be easier to use separate ...