Cheapest O2 kit?
 

For those who have a carburetor and need tuning, is there like a cheap kit, that you can buy, where you can just slide an O2 sensor in your exhaust pipe, and measure the A/F levels?

Most of the kits require you to screw in the O2 sensor in the exhaust pipe. But most scooters/motorcycles have no provision for that; and I don't want to damage my exhaust.

Those kits are all $100+ kits...

Any other solutions?

I used to have a exhaust reader that slid down into the exhaust end to read Lamda and air/fuel ratio. It was ancient and huge but worked great. I sold it and kinda regret it now. I know Koso sells one but I don't recall if it bung attached, like you are trying to avoid, or if it slides down into the exhaust end.

The reason they mostly use the bung attachment is because modern exhaust use catalytic exhaust and any reading after the cat will give a false reading if read after the cat, hence the bung before. The exhaust we used our old school one on were expansion chambers on 2-strokes. No cats in those.

If I tune now I just do plug chops. It's time consuming and annoying but it works. I'm in the process of putting a bigger main jet in my Buddy 125 when I get off my butt.

Funny, I just revisited this thread, and I now have an aftermarket exhaust that has a provision for an O2 sensor.
I just need a cheap O2 sensor, and a way to read the data.

Koso makes one but its money. I'm not aware of any affordable ones. But the bung mounted ones make hook-up easy. We had a few "popular" 2-stroke exhaust on hand with bung connections welded in so we wouldn't have to molest a new Yasuni, LeoVince, Tecnigas or Stage 6 expansion chambers.

Are you looking for a basic air/fuel ratio readers or a more advanced lamda type one? I had a Koso that did both and collected crazy data before doing a BBK kit on my Adly RT 50 (the scoot that brought me here) because the sealer was very sketchy about what they did for the warrant carry-over install. It seemed good after the BBK install data-wise but I donated the scooter not long after the install.