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Discussion Starter #1
This seems to be an known issue. It's difficult to smoothly crack open the throttle a little, or to roll off that last little bit smoothly. Disrupts my turns. I'd like to fix that!

I was thinking about the throttle [position] sensor. The service manual has specs on it, but it also states to not remove or adjust it. Has anyone played with that sensor?

Of course, I'll check the throttle cables. What else might cause the problem?
 

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Problem is emissions, because two things are happening to make the throttle response jerky:

1 -- the Air Fuel Ratio is around 14.7 parts air to 1 part fuel at low throttle positions... as ideal as that may be for the environment, it's not a smooth throttle but a jerky one. Idle is fine at this AFR but otherwise it needs to be 13.2 to 13.6 AFR for smoothness. A narrow band O2 sensor on the latest models keeps it around 14.7 AFR... so there you have two options. One is a narrow band sensor controller to richen up that area, and I'm not sure if that's available for the late models (look for a sensor at the exhaust collector top-side to determine if you have the sensor). The other option regardless is a Flash Tune to both remove the closed loop tuning at the low power settings and properly set AFR.

2 -- whenever you let off the gas at almost any RPM, the bike is tuned to run on very little fuel, which is a super lean condition, and as soon as you crack open the gas, it surges. Again, this is for emissions. This can only be fixed by a Flash Tune also, and can also reduce engine braking a little which helps (even with the slipper clutch)
 

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Glad OP posted this, I notice the same thing but didn't know how to describe it.

Man I wish TuneECU worked with the N300. :(
 

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Discussion Starter #4
Makes me want to program a microcontroller to override the ECU. Good thing there's a kill switch!
 

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Discussion Starter #6
With all that in mind, could my Yoshimura slip-on be making the lean condition worse enough to make a notable difference in throttle on/off response?

Problem is emissions, because two things are happening to make the throttle response jerky:

1 -- the Air Fuel Ratio is around 14.7 parts air to 1 part fuel at low throttle positions... as ideal as that may be for the environment, it's not a smooth throttle but a jerky one. Idle is fine at this AFR but otherwise it needs to be 13.2 to 13.6 AFR for smoothness. A narrow band O2 sensor on the latest models keeps it around 14.7 AFR... so there you have two options. One is a narrow band sensor controller to richen up that area, and I'm not sure if that's available for the late models (look for a sensor at the exhaust collector top-side to determine if you have the sensor). The other option regardless is a Flash Tune to both remove the closed loop tuning at the low power settings and properly set AFR.

2 -- whenever you let off the gas at almost any RPM, the bike is tuned to run on very little fuel, which is a super lean condition, and as soon as you crack open the gas, it surges. Again, this is for emissions. This can only be fixed by a Flash Tune also, and can also reduce engine braking a little which helps (even with the slipper clutch)
 

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With all that in mind, could my Yoshimura slip-on be making the lean condition worse enough to make a notable difference in throttle on/off response?
It should be negligible; there may be minor changes to your torque curve (they usually exacerbate the existing flat spot slightly), but every slipon out there is tested on a stock map, and you can bet that's where the majority of them are used (including my own).

You can get buy and install a fuel controller from Area P or Power Commander loaded with an appropriate map - it should be enough to fatten up fueling to get rid of the spiky response. Bear in mind there's no free lunch; more go-go juice means slightly poorer MPG; it is inevitable.

You can mail Area P's Kerry, he's very helpful with these kinds of queries.

Bottom line is they'll all tell you stock fuelling is pretty crap, the question is, is it crap enough for you to go to the trouble of a fuel controller?
 

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As luck would have it, I found my notes about my slip-on install. I had exactly your concerns before I bought it.

I've got a Leo Vince Corsa GP, I use the sound insert as I think this config is the recommended one on a stock map. It's also antisocially loud without it; it's pretty loud anyway...

  • Didn't note any difference in performance at all, even if Dyno chart suggested a wee dip around 6k. There is the psychological effect of more noise, though.
  • Engine note is way more prominent low down; it's about the same as stock at freeway speed (some people hate slip-ons at freeway pace). This low speed sounds make you more aware of the engine's fueling and characteristics; you can hear the fueling cuts very clearly on a straight pipe.
  • No idea about fuel economy as I commute and carry vastly different weights; it has a huge effect on consistency. Not much different, I still fill up every five days.

I'm still interested in a controller at some point but I'll probably go for a full system at the same time. At the moment I'm pretty pleased with my setup.
 

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Problem is emissions, because two things are happening to make the throttle response jerky:

1 -- the Air Fuel Ratio is around 14.7 parts air to 1 part fuel at low throttle positions... as ideal as that may be for the environment, it's not a smooth throttle but a jerky one. Idle is fine at this AFR but otherwise it needs to be 13.2 to 13.6 AFR for smoothness. A narrow band O2 sensor on the latest models keeps it around 14.7 AFR... so there you have two options. One is a narrow band sensor controller to richen up that area, and I'm not sure if that's available for the late models (look for a sensor at the exhaust collector top-side to determine if you have the sensor). The other option regardless is a Flash Tune to both remove the closed loop tuning at the low power settings and properly set AFR.

2 -- whenever you let off the gas at almost any RPM, the bike is tuned to run on very little fuel, which is a super lean condition, and as soon as you crack open the gas, it surges. Again, this is for emissions. This can only be fixed by a Flash Tune also, and can also reduce engine braking a little which helps (even with the slipper clutch)
This seems to be an known issue. It's difficult to smoothly crack open the throttle a little, or to roll off that last little bit smoothly. Disrupts my turns. I'd like to fix that!

I was thinking about the throttle [position] sensor. The service manual has specs on it, but it also states to not remove or adjust it. Has anyone played with that sensor?

Of course, I'll check the throttle cables. What else might cause the problem?
Arizona is describing DFCO. Deceleration fuel cut-off comes on when you cut throttle and the engine is above idle, it'll shut off the fuel injectors until just above idle. This was what was actually the issue in the first year of ninja 300s was that the ECU wasn't turning the injectors on soon enough so the engine would stall. This was originally set at around 1000 RPM but when you'd pull the clutch in at the tail end of a stop where you were higher than idle, the bike would die because by the time the fuel kicked back on, it wasn't enough to keep the engine running.

I believe the issue you're experiencing with the jerky throttle is more due to the cheap ECU and TPS. Other modern, and much more expensive bikes with better ECUs and sensors also have DFCO and adjust fueling at low RPMs but don't jerk when you let off the throttle or crank it back on.

I personally believe the issue is that the TPS isn't 100% calibrated true to the actual throttle and can't be due to the cheaper design of the ECU and sensors. That jerking you feel when you let off the throttle is that just BEFORE you've closed the throttle all the way, the fuel is completely cut and you notice it as sudden engine braking at partial throttle. When done properly, the fuel cutoff happens right when the throttle butterflies close so you wont get any jerking. The problem is that with the throttle partially open, it's still pulling in a good quantity of air, but loses fuel just before fully closed and this sudden loss of power is what you're feeling.

It's the same when you're rolling on the throttle. You roll on the throttle a little bit and the butterflies start opening but the ECU and TPS hasn't quite caught up yet. You now have the engine sucking in quite a bit more air in than it would at idle and then the fuel hits and it's a very sudden burst of power.

TLDR: I believe it's a consequence of a cheap ECU and it's throttle monitoring function which can be masked by enriching the fuel mixture a bit to cover up the flaw.
 

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Discussion Starter #10
I personally believe the issue is that the TPS isn't 100% calibrated true to the actual throttle...
So what if I just adjust the TPS a little? The service manual refers to it as the "throttle sensor" if you search for it. There is also a "sub-throttle sensor," which is something new to me.
 

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I noticed certain RPM bands and gears are much worse for it. Coasting along around 15mph in 3rd on the level is a good example, you can hear this slight burr...burr...burr...burr and gentle rocking as the fueling dips up and down. Before my new muffler I thought it was just a rubbing brake disk or some chain tightness. Opening the throttle just a tiny bit, or even going up a gear and dropping revs can smooth it out.

With reference to Freelancer's remarks, I understand it's much worse on some other bikes due to the higher displacement, notably the FZ07 and even the venerable Ninja 650.
 

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So what if I just adjust the TPS a little? The service manual refers to it as the "throttle sensor" if you search for it. There is also a "sub-throttle sensor," which is something new to me.
Probably not going to help. The cheaper sensor suits they use on these newer budget bikes and the older bikes aren't very good at very tiny minute measurements which is where the issue sets in. You can't adjust to fix this issue on the Ninja because that tiny little mm of adjustment left on the throttle keeping the butterflies barely open is literally imperceptible to the sensors themselves. They don't have that sensitivity to sense that barely cracked throttle because the general application and low level of ECU doesn't need or can even use a much more sensitive throttle sensor suite which is a much more sensitive sensor and has a lot more updates per second on the ECU end than what the cheaper Ninja 300 ECU can cope with. You have to remember that the budget ECUs in the small bikes now are the same level as bikes from 20 years ago. The new-gen sports and super bikes of now are getting the nicer ECUs and sensor suites with a much higher polling rate which it can see and adjust to very fine throttle positions.

Hell my 07 GSX-R 750 does the same thing. I can very slowly roll off the throttle and feel where the ECU thinks my throttle is off but I still have the throttles open by a few degrees. This though is actually common on older gen bikes such as this and is often "fixed" by enriching the fuel mixture up a bit. The reason why Sulman mentions those newer bikes with this issue is that it does get more pronounced with a larger displacement and the bikes he mentions are still considered bargain basement bikes and get the cheapest electronics money can buy. A brand new gen super sport or super bike pretty much has almost all of the abrupt fueling sorted with a much better ECU and better quality sensors. Even the new gen GSX-Rs are much better in comparison to an older gen like my 07. Although it's very easy to work around and just means I'm carrying a higher RPM and a gear lower than the practically lugging it gear I was in earlier. Although I hear the R6 has had this issue since gen 1 and it doesn't stop it from being one of the best amateur race bakes you can get for its class so herky jerky throttle due to the ECU isn't as bad as it may be getting blown up to be.
 

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Discussion Starter #13
Starting to wonder: Is the cost and trouble of getting a fuel controller worth not having a carburetor?? I mean, it sounds like fun to play with, but it seems wrong that I need to spend money just to make the bike run normal.
 

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Discussion Starter #14 (Edited)

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I am also having the same issue with the jerky throttle from 0%-5%. I tried the numerous fixes such as tightening the throttle cable and chain with modest improvements.
I noticed that when it's cold in the morning the effect is much less pronounced, at least until the bike warms up. Has anyone else notices this? I also noticed it becoming worse after installing my Akrapovic slip-on, although it's been so long I can't even remember how it rode back then.
My intention was to install a PCV, but to be honest I don't think I'm ready to spend upwards of $600 for a proper tune at this point. I also ordered a K&N air filter so we'll see if that helps.
About that EJK fuel controller - at $250 it would be cheap enough to consider if it helps mitigate the issue. If you feel like buying it, please write back with your results!
 

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Discussion Starter #16 (Edited)
I am also having the same issue with the jerky throttle from 0%-5%. I tried the numerous fixes such as tightening the throttle cable and chain with modest improvements.
I noticed that when it's cold in the morning the effect is much less pronounced, at least until the bike warms up. Has anyone else notices this? I also noticed it becoming worse after installing my Akrapovic slip-on, although it's been so long I can't even remember how it rode back then.
My intention was to install a PCV, but to be honest I don't think I'm ready to spend upwards of $600 for a proper tune at this point. I also ordered a K&N air filter so we'll see if that helps.
About that EJK fuel controller - at $250 it would be cheap enough to consider if it helps mitigate the issue. If you feel like buying it, please write back with your results!
My EJK is on its way. I should have it by this weekend.

Look for a link at the bottom of the EJK page to apply for a discount code.

If the slip-on made the throttle worse, a higher flow air filter will either do nothing or make it worse, I think. Most people suggest that the problem is to much air flow. The EJK is going to add more fuel into the mix.
 

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I am also having the same issue with the jerky throttle from 0%-5%. I tried the numerous fixes such as tightening the throttle cable and chain with modest improvements.
I noticed that when it's cold in the morning the effect is much less pronounced, at least until the bike warms up. Has anyone else notices this? I also noticed it becoming worse after installing my Akrapovic slip-on, although it's been so long I can't even remember how it rode back then.
My intention was to install a PCV, but to be honest I don't think I'm ready to spend upwards of $600 for a proper tune at this point. I also ordered a K&N air filter so we'll see if that helps.
About that EJK fuel controller - at $250 it would be cheap enough to consider if it helps mitigate the issue. If you feel like buying it, please write back with your results!
niciuffo, since you're in Switzerland and your bike is an European Model the solution for your Ninja is quiet easy.
Get a Lambda (O2-Sensor) Eliminator, disconnect your O2-Sensor and plug the eliminator in instead of the sensor = problem solved.
Important notice, you need this eliminator in any way even if you go and buy a fuel-adjusting unit.

Read the link please: http://www.powercommander.com/downloads/211/install/optimizer/eng76423007.01.pdf
And something more to read: http://www.polo-motorrad.ch/de_ch/oxygen-sensor-23021-kawasaki-125751.html

PS: You should not care to much about an American Model of the EX300 since the ECU is really different to the rest of the world (idk what's used in Australia).
 

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Discussion Starter #18
My American model 300 does not have an O2 sensor in the exhaust pipe.
 

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Thanks, I didn't even know my bike had an oxygen sensor. I tried removing the connector but I couldn't, it's just stuck there. Did you remove it yourself and have any tip you could share?
 
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