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2017 Ninja 300 ABS
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So I got a 2017 and I bought a Yoshi Full System Exhaust from some guy on Offerup but the system doesn't have a port for the O2 sensor so my sensor is just hanging out. But I added a 13t front sprocket and 45t rear sprocket and a K&N air filter to the bike and well idk if it's because I haven't tuned or flashed it at all, but the spedometer at redline reads 118mph. What I'm asking is, can I trust that or is it something with not being tuned idk? Cuz I thought the max speed on it was 110
 

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That speed will never change - it will always read 118 max at redline in 6th, because the speed sensor is on the front sprocket countershaft nut. You may need a speedo healer or similar to get an accurate reading. Your actual speed will obviously change with a sprocket change though.

As for the O2 sensor, you probably want to find someone who can weld on threads and then tune it... You might make the mixture be pretty far off by putting a full exhaust on a bike with no tune. This has nothing to do with tuning the motor or not.

Hope this helps.
-Mike
 

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Have you done the PAIR delete? If you're going to tune it, you may want to do that before the tune too, as it may change the AFR.

When I got mine, it had already a full Yoshi system, and the 02 sensor wasn't there anymore.
The previous owner told me the bike wasn't tuned. It did run very well.
I later added K&N filter, PC5 and deleted the PAIR system. I felt a slight difference, nothing great. The bike still ran very nice, and it still does.

With stock gearing and a 160/60 tire on the rear I was still seeing 118 on the dashboard. I now run a stock size 140/70 tire on the rear and the max I see on the dashboard is 115, which is probably closer to the actual speed.
 

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Have you done the PAIR delete? If you're going to tune it, you may want to do that before the tune too, as it may change the AFR.

When I got mine, it had already a full Yoshi system, and the 02 sensor wasn't there anymore.
The previous owner told me the bike wasn't tuned. It did run very well.
I later added K&N filter, PC5 and deleted the PAIR system. I felt a slight difference, nothing great. The bike still ran very nice, and it still does.

With stock gearing and a 160/60 tire on the rear I was still seeing 118 on the dashboard. I now run a stock size 140/70 tire on the rear and the max I see on the dashboard is 115, which is probably closer to the actual speed.
Does that cause any issues? Is there something that needs to be done if it's not in the pipe?

In another thread, a member is having running issues with a bike that has an aftermarket pipe and no sensor. I suggested that may be the cause of the problems.
 

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Uhhh what's this?
There is a hose that goes from the intake air box to the valves cover to add fresh air to the exhaust gases. It's controlled by a valve that is halfway in the hose and it's supposed to help to make cleaner emissions.
The mod consists of removing the hose, plug the air box and put a cover in the valves cover that you can find on eBay for about $10.
If you don't do it, it's said that the bike cannot be correctly tuned because this clean air from the air box is modifying the AFR and confusing the tuner.
I speak for what I've heard. I knew about it, so when it was time to check the valves I took it out and put the plugs. I didn't feel any difference after doing it.
 

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Does that cause any issues? Is there something that needs to be done if it's not in the pipe?

In another thread, a member is having running issues with a bike that has an aftermarket pipe and no sensor. I suggested that may be the cause of the problems.
Not that I know. I bought my bike in 2016, with 2000 miles. It already had the full Yoshi and no O2 sensor. PO told me it wasn't tuned, and the bike ran just fine.
I don't even know where the O2 sensor joins the main harness because it's not there and I have no hanging wires or anything like that.
 
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