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Hey guys, recently bought a 2018 Kawasaki Z125 with a couple goodies, including a TB 143 cc big bore kit, race head, race cam, Z-AFM 4.9 self fuel mapping module, MNNTHBX silicone intake and more. I'm relatively new to the bike life and barely beginning to learn and understand them. The guy who sold me the bike also gifted me a full yoshimura exhaust kit. However there is a hole where the o2 sensor should've been. I believe because of this the bike is throwing a check engine. If anyone knows of any such device or tune that would eliminate the code please inform me. Also if anyone can give me any sort of direction as to what to look out for check that would be much appreciated.
 

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If that Z-AFM comes with an autotune function, then you will want an O2 in the exhaust, normally those modules include a connection for the stock O2 sensor connector to stop the error code.

If you don't have the autotune module, then Kawasaki Brad has a cheater you can plug in to get rid of the fault code.
 

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Can you post a photo of this "hole" in your Yosh exhaust? The Yosh pipe comes with a small 12mm bung for the stock O2 sensor so I had to cut that off before I could weld on an 18mm bung to mount the wideband sensor the AFM uses. So I'm guessing the pipe's former owner might have been mounting up the wideband sensor but didn't finish the job. Stainless steel 18mm sensor bungs are easy to find but I'd caution that a lot of them are too short and will push the sensor too deep into the Z125's small exhaust and block your exhaust flow. Here's a photo of what you want: 25mm long with a fishmouth so it fits the tube properly and just the end of the sensor in the exhaust flow. Almost any automotive bung can be made to fit, but some will fit better and won't block the exhaust too much. Also do you have a local welder who you trust welding thin wall SS tubing?
Wideband sensor depth.jpg Yosh bung depth.jpg
 

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Actually, newer Yoshimura exhausts, specifically the RS-2 and not the 'JDM' model R-77s, are now fitted with an 18mm bung. I don't know when they made the switch but I just confirmed this two weeks ago when I was looking at exhausts.
 

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I also believe he sells the cover for the location of the sensor on the exhaust.

Heres the bundle of both:
Your other option is paying double that to bring it from Europe.
Thanks for the mention Azlar and Greg
@[email protected]$$ yes it comes with the O2 eliminator and the plug for your exhaust. The 12mm is usually what you want for the 125 but as @MileHayabusa mentioned some of the aftermarket stuff is the 18. If you want to order one I'll throw in the 18mm plug no charge so you'll have both. Just make a note at the checkout to remind me.
 

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I wouldn't recommend running without an O2 sensor of some type, if you eliminate the stock one then you should still have a wideband sensor installed for a piggyback system at least, tricking your ecu will put it in an area in the timing maps that is not always the best place to be for power or safety, you also wont be at optimal air fuel ratio without some type of sensor, its there for a reason and that reason is not for emissions in this case as there is no bank two sensor installed, the bank one sensor is for fuel trims in a closed loop system.
 
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