[Kaw'ee]

Greg, that would be MAP sensor, huh?

Does anyone even know if the O2 on this bike is used throught the rev range or just at closed or WOT?

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My understanding so far is
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At start up it is in OPEN LOOP (no signal)
When no signal is received from the O2 sensor, as is the case when a cold engine is first started (or the 02 sensor fails), the computer orders a fixed (unchanging) rich fuel mixture. This is referred to as "OPEN LOOP" operation because no input is used from the O2 sensor to regulate the fuel mixture.
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When the o2 "heat" sensor gets to 600 degrees , then it turns it into CLOSED LOOP
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Stays in CLOSED LOOP until WOT , then gos into OPEN LOOP

 

[Kaw'ee]

I got a comment on my YouTube channel from a subscriber that tried it on his grom .
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Dirty ol Joe
1 hour ago
It worked out perfect. My engine light didn't come on either but I disconnected the battery before I started it but it is a noticeable difference. Ill give a shout in the next video if I'm not too drunk to remember, eventually I will it just takes time.

 

[Fox Fader]

I do know Victory works a bit differently, O2 is not always sending a signal to trim fuel.

Without looking at the parts list, I'm pretty sure there's no map or knock sensor here.

If the O2 on this bike is a 4 wire system, unplug the black wire, which is the signal wire and keep the others plugged in. This should keep the MIL off. The ECU just needs to "see" the O2.

Edit; I'm sorry, you don't have a bung.

 

[Kaw'ee]

FOLLOW-UP ............
The bike is fueled very lean for emissions reasons, that is the bike when stock runs nearly at dangerously lean levels. Installing intake and exhaust mods severely exacerbates the problem. Therefore you need to buy the expensive fuel controllers just so it will run safe and better, But of course you can make it run WAY BETTER when using one opposed to just a safe and better
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Just got some more confirmation from MrEvilpirate EFIE thread that just un-plugging the 02' sensor does make the bike run RICHER.
https://www.z125owners.com/forum/engines-discussions/15405-efie-experiences-3.html

What hes doing is a little over my head but...
I Will be following his results because it is the right way to do it and avoid buying the fuel controllers and having to learn all that

If you want to avoid even the EFIE mod and just trying to get your bike to run safe and better and not be to lean.
Then try un-plugging your 02' sensor but leave it in place or plug off the bung.
This is what I'm doing right now and its running better than it ever has,
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If you disconnect the 02 sensor, you'll run as rich as the ECU set fuel tables will allow.
so by design it won't hurt anything, and by dumb luck it seems to be better than when the 02' is connected
The ECU will take a while to compensate and adjust to proper AFR. During this "adjusting" period, the bike will be a bit rough.. Mine corrected after a couple of 20 minute (or so) rides
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DOWNSIDE.................
My check engine light is on , but only till i figure out how to trick it.
I've read I'll will lose some MPG's , but getting 80mpgs now so its worth the trade off
I wont have the benefits of the compensating that come with the 02 that Greg-E mentions ...........
(It won't be able to compensate for altitude or air pressure changes as well without the o2, a few other downsides like compensating for crap fuel.)
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This trick will probably only work when your only doing just the PIPE n INTAKE mod' from what I'm reading.

 

[Greg_E]

Other downside is that it might wreck the o2 sensor, not sure exactly what type of sensor we have, but the wideband sensors warn against running them disconnected.

 

[Kaw'ee]

FOLLOW-UP ............
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This trick will probably only work when your only doing just the PIPE n INTAKE mod' from what I'm reading. Then try un-plugging your 02' sensor but ..."WRONG"(((leave it in place)))"WRONG" ...or plug off the bung

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MrEvilpirates testing has shown THERE'S NO DANGER of a LEAN CONDITION when installing just a intake & exhaust
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Therefore Unplugging the 02 sensor IS NOT NECESSARY. (see bottom link)
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If you run the bike without the 02 sensor for better performance at the 25% to 75% range or any reason (stripped threads or no bung) his testing has shown IT DOES RUN LEANER @ 15.1 AFR at just passed idle (cracked throttle) to 25% throttle. this is on a stock bike . So Intake & pipe could raise it even more and not be worth the risk of running leaner (your call)
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EDIT { "WRONG"(((leave it in place)))"WRONG" }
As greg added DO NOT RUN THE 02 INSTALLED WITHOUT BEING PLUGGED IN. Install a cap off plug.
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Good advice From MrEvilpirates thread
For Kaw'ee and guys running O2 deletes, be advised that the "closed" loop without the O2 tends to run lean. I was seeing numbers over 15. This was on stock bike. I didn't take readings with mods. So at idle or cracked throttle/cruise, without O2, you are lean. It does richen at 3/4 and WOT compared to stock. I suppose that cracked throttle AFR being lean MAY be acceptable because there is minimal load on the engine. When you decelerate the mix leans out to the point where it can't be measured on the gauge... but I personally would not be comfortable. Kaw'ee... I think you mentioned your idle temps went up when you deleted the O2. This is why.
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This was on stock bike. I didn't take readings with mods.
Results without factory O2 in place:
Cold Idle: 12.8 - 13.0 AFR
Warm Idle: 12.8 - 13.0 AFR
Cruise, throttle just cracked to maintain speed: 14.8 - 15.1 AFR
25% - 75% Throttle (gear/speed made no difference): 13.0 - 14.0 AFR
RPMs Over 8k, regardless of throttle position: Around 13 AFR
WOT: 12.0 AFR, dead nuts, 12.0.

Personally If I were you guys with no O2 I'd just weld the bung on and call it a day.
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https://www.z125owners.com/forum/engines-discussions/15405-efie-experiences-5.html#post122949