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Since you're not sure of the thread size, why not take the bikes o2 sensor to a local auto parts store where you should be able to match up the threads to the correct plug size? Probably cost a lot less, plus there is the chance that you may end up with the wrong size from Amazon.
 
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Discussion Starter #3 (Edited)
I'd tell you honestly, that I don't know if the wiring allows me to safely remove the O2 sensor.
It appears to me that the sensor is permanently wired to the wiring harness. Not sure if it has a plug somewhere on the sensor itself.
I'm perhaps a bit careful not to break it...

The website here : http://www.magnumtuning.com/en/deta...-oxygen-sensor-universal-wiring/honda/cbr300r , says that the O2 sensor has M18x1.5mm thread

I'm going for this one though, simply because I prefer to use a regular wrench over an allen wrench:http://www.amazon.com/Berk-Technology-BTO2-Plug-Universal-M18x1-5-17mm/dp/B008HRX5PU/

I'm also buying these washers for the O2 sensor, to do more tests with:http://www.amazon.com/Honda-Genuine-Automatic-Transmission-Washers/dp/B00ET6UXLC/
 

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What would you recommend for plugging the o2 sensor hole in the exhaust pipe?
I'd like to run some tests without o2 sensor, but have to find something to plug the hole.
A spark plug has a too small diameter.

You think this 18mm plug will do?

https://www.amazon.com/gp/aw/d/B005HR155A/
Hi MeeLee. I just removed my O2 sensor today. It is easy to remove. Follow the wire from the header pipe about six inches and you will find the connector. Mine removed from the bottom by squeezing the side to release. At that point you can free the wire and use a wrench to remove the sensor.

I used a M12-1.25 oil drain plug and a copper washer as a bung plug. The two parts cost about $8 combined. :)
 

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Discussion Starter #6
it should be a standard size O2 thread size. Plenty of plugs on Amazon...I got several plugs and bungs.

With the the O2 sensor out the bike will go into limp mode shortly after
I think i might just keep it plugged in then, probably either mount it outside of the exhaust pipe, or use a few washers to raise it up from the exhaust pipe by 2 to 3mm.
 

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When you guys removed your O2 sensor did you check engine light come on? I just unplugged mine, not fully removed, and about 10 min into my ride my check engine light came on.
 

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When you guys removed your O2 sensor did you check engine light come on? I just unplugged mine, not fully removed, and about 10 min into my ride my check engine light came on.
If you unplug the wire harness for the O2 the check engine light should not come on. There are many 300 and 250r owners who have removed the O2 sensor completely or just unplugged it and never had the light come on. I have never heard of that happening at all.
Was the light blinking?

I have my O2 sensor, Purge valve, and IACV all unplugged and never had my light go on.
 

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If you unplug the wire harness for the O2 the check engine light should not come on. There are many 300 and 250r owners who have removed the O2 sensor completely or just unplugged it and never had the light come on. I have never heard of that happening at all.
Was the light blinking?

I have my O2 sensor, Purge valve, and IACV all unplugged and never had my light go on.
All I did was unplug the wire that goes to the side of the bike, maybe thats the issue? I'm probably going to plug it back in and see if the light comes on again, if so it may be a whole other unknown issue. The light was only solid when it came on, once I shut off the bike when I arrived at work, turned it back on, it was not on again.
 

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All I did was unplug the wire that goes to the side of the bike, maybe thats the issue? I'm probably going to plug it back in and see if the light comes on again, if so it may be a whole other unknown issue. The light was only solid when it came on, once I shut off the bike when I arrived at work, turned it back on, it was not on again.

If you remove the entire O2 sensor it gets unplugged on the left side attached to the frame. I have never heard of a light going on by doing that. Is it a California model? If it is it may be due to their strict emissions. I'm not sure about that but California bikes may trigger a light if you tamper with any emissions parts.
Even though you do not live in California it may be still possible you have a Cali bike. The starter of this thread lives in Florida and bought his bike in Florida and it turned out to be a California model.
Well keep an eye on the light and see if it comes on again. Did you feel any loss in performance? Your fuel controller is handling the fuel ratio anyway. Almost every car I've had shows the check engine light. I put a piece of black electric tape over it lol
 

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If you remove the entire O2 sensor it gets unplugged on the left side attached to the frame. I have never heard of a light going on by doing that. Is it a California model? If it is it may be due to their strict emissions. I'm not sure about that but California bikes may trigger a light if you tamper with any emissions parts.
Even though you do not live in California it may be still possible you have a Cali bike. The starter of this thread lives in Florida and bought his bike in Florida and it turned out to be a California model.
Well keep an eye on the light and see if it comes on again. Did you feel any loss in performance? Your fuel controller is handling the fuel ratio anyway. Almost every car I've had shows the check engine light. I put a piece of black electric tape over it lol
It is entirely possible that it is a California model, though I'm not sure there is any way I could check that. As far as I could tell in the quick ride this morning there wasnt any change in actual performance though it did seem to be running significantly richer than before, that and the fan actually turned on which is unusual because it wasnt terribly hot this morning and the ride was only about 20 min.
 

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It is entirely possible that it is a California model, though I'm not sure there is any way I could check that. As far as I could tell in the quick ride this morning there wasnt any change in actual performance though it did seem to be running significantly richer than before, that and the fan actually turned on which is unusual because it wasnt terribly hot this morning and the ride was only about 20 min.
I wouldn't worry about the fan too much. A lot of people with the EJK have noticed an increase of fan time. You can look in the engine bay and to the rear of the engine towards the airbox if it was a Cali model you would have an Evaporator Canister. Do you know what they look like? Slightly above and to the rear of the starter.

Do you have the Hi-viz matte black/yellow model?
 

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I wouldn't worry about the fan too much. A lot of people with the EJK have noticed an increase of fan time. You can look in the engine bay and to the rear of the engine towards the airbox if it was a Cali model you would have an Evaporator Canister. Do you know what they look like? Slightly above and to the rear of the starter.

Do you have the Hi-viz matte black/yellow model?
I will have to take a look, and no I have a red CB300F, I have been meaning to get a picture of it on here but I still have to put on the wheel tape which I'll probably be doing this weekend.
 

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I will have to take a look, and no I have a red CB300F, I have been meaning to get a picture of it on here but I still have to put on the wheel tape which I'll probably be doing this weekend.
Oh ok I was just wondering because the starter of this thread (who isn't a member anymore) had that color model. Also I did just do a quick search and though not specifically this bike but other bikes that are Cali models the users say any tampering with critical emissions equipment will trigger the light throwing an error code. It is most likely stored in your computer. If you are that worried Honda can hook up to it and figure it out. There is also a cheap way for you to tap in and possibly find out the code but that's an entirely different ballgame lol
 

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Oh ok I was just wondering because the starter of this thread (who isn't a member anymore) had that color model. Also I did just do a quick search and though not specifically this bike but other bikes that are Cali models the users say any tampering with critical emissions equipment will trigger the light throwing an error code. It is most likely stored in your computer. If you are that worried Honda can hook up to it and figure it out. There is also a cheap way for you to tap in and possibly find out the code but that's an entirely different ballgame lol
I'll have to see if it is that type of model or not. I'm not certain but I dont think leaving the O2 plugged in would hurt the bike at all, just not allow the EJK to run completely which honestly after how rich it was this morning is not a bad thing. It was honestly running better before it was unplugged. And I only joined this forum about a month ago but had been lurking for a while. Thanks to all of you guys I had all the info and more that I needed to modify my bike. These little bikes pack quite a punch for their size and I'm gonna hold onto this well beyond getting my next bike, most likely a 2006 GSX-R 600 my buddy is about to sell to me for cheap.
 

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I'll have to see if it is that type of model or not. I'm not certain but I dont think leaving the O2 plugged in would hurt the bike at all, just not allow the EJK to run completely which honestly after how rich it was this morning is not a bad thing. It was honestly running better before it was unplugged. And I only joined this forum about a month ago but had been lurking for a while. Thanks to all of you guys I had all the info and more that I needed to modify my bike. These little bikes pack quite a punch for their size and I'm gonna hold onto this well beyond getting my next bike, most likely a 2006 GSX-R 600 my buddy is about to sell to me for cheap.
Does your bike model have a "C" at the very end of it? If it does I think that means Cali. Like CBR300aC
Did you alter the EJK settings at all or have you kept it 'stock' the way you received it? Removing the O2 sensor with the present settings it came with is how they tested the bike. They require removing the O2 so you aren't constantly fighting the PGM-FI system that will constantly be reading the O2 and trying to adjust the mix.
UGH don't say gixxer!! haha. I personally have an issue with them. Basically, because everyone in Florida has one and with it comes their attitude. They all think they are professional racers or something and look down on every other bike. Very good bikes though
 

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Just finally got the time to take a look, there is definitely an evaporated canister right there, so it is definitely a cali model then, weird considering I bought it on the east coast.
 
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Just finally got the time to take a look, there is definitely an evaporated canister right there, so it is definitely a cali model then, weird considering I bought it on the east coast.
The original poster of this thread has a Cali bike and lives in Florida. So to answer your question about the engine light that's your answer. Cali emissions won't let you mess with anything. It probably doesn't affect the driving or go into limp mode though
 
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