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According the UK riders, it's cod 25, Speed Sensor.


Not sure if UK and US ECUs are the same, but gear position indicator going blank makes sense, since the the ECU derives gear position from engine speed and wheel speed. When those two readings exceeds the factory-set tolerances, ECU cannot reconcile the differences and says: "NO BUENO".
 
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FWIW, similar problem can occur when you go other way with the sprocket change. Here's a 2018 Z1000 rider that went with a shorter gear ratio and got a similar gear indicator fault too.


Not sure if their 2018 Z1000 have the same TC/ABS and IMU systems as North American and Aussie bikes.
 
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2019 Ninja 1000 ABS w/ Akrapovic Slip Ons.
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Thanks. I am preparing myself emotionally for undoing this mod. In a couple of days the new sprocket nuts and washers arrive. I guess I will use them to put back to stock...
 

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Volfy, that article is over 10 years old, and it also started off talking about about the "xr," as the current, state of the art BMW s1000xr. They don't do much racing on that platform.

If you care to learn about the systems that are available, it's important to read the article, 100,%....or even 75%.

Over time, things changed. The gps thing eventually became a real thing, in Moto Gp. At one point, they had the gps coordinates programmed into the ECU, for every track. The system knew the bikes position and was able to limit power, based on the bikes location on the track. This was important in a race, for obvious reasons, but it was also to help with fuel economy. Limiting wheel spin avoided wasting fuel as well as helped with acceleration.

But, we are now up to 2020 technology with the ninja 1000. Even as early as the 2017 version, the ECU was very aware of tire profiles, and it still is. This is mentioned in the 2017 owners manual your bike was supplied with. The reason it's not an issue has to do with the allowances built into the system to deal with tire wearand no doubt the slightly different profiles of replacement tires. It's also set to a beginner level of intervention.

If you look at a similar system on Hondas 2017 cbr1000rr. Like the one jjsc6 has...not the new 2021rrr-rrr edition. The new model already has the 55 rear., The 2017 won't even allow a 190/55 rear tire without throwing an error.

Changing any of these base calibrations....tire size, or gearing, is playing with fire if you expect any of these systems to save you. Seriously, there are alternatives. The Versus 1000 is more comfortable. There are also 7 model years of the ninja where you can screw around all you would like to. À
 

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Thanks. I am preparing myself emotionally for undoing this mod. In a couple of days the new sprocket nuts and washers arrive. I guess I will use them to put back to stock...
It's good to be prepared for that. I would stay with it just to see if it does trigger a fault. As I mentioned above, the TC/ABS systems are working, as long as it hasn't throw a code. From what the UK rider stated, just the 16T will probably be okay. He had no problem after replacing the 39T with the stock 41T (16T still on). I've ridden with a 39T rear for more than year now, with no ill effect. 39T alone is very close to 16T alone, which is just a tiny bit taller gearing.

Your 16T + 40T puts your set up in iffey territory. You might get away with it... or not. I would expect the same if somebody does a 16T with a 190/55 rear.

If you do get a fault, you have the option of undoing either the 16T front or the 40T rear. Either one should put you back to no fault territory. No need to undo both, unless you want to.
 

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But, we are now up to 2020 technology with the ninja 1000. Even as early as the 2017 version, the ECU was very aware of tire profiles, and it still is. This is mentioned in the 2017 owners manual your bike was supplied with.
I'd like to know where exactly in the Owner's Manual that states the ECU is aware of the OEM tire profile and allows nothing but. Which page(s) is that on?

I appreciate your concern. Us controls guys have a saying in our circles: "Only those who make the rules are allowed to break the rules." The second, accompanying, adage to that is: "Only those who understand the rules are allowed to test the rules."

Anybody who makes any modifications to his motorcycle would be wise to keep those rules in minds. That includes all of us.
 
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One thing to keep in mind is that, for all the related cases I've come across, the fault code seem to be "gear indicator" or "gear shift indicator". No where does the code say "TC failure" or "ABS failure".

When this issue first cropped up on 2017 bikes, everybody just assumed it was related to the 6-axis IMU... because that is what EVERYBODY knows was a major addition to the 2017+ update. What almost everybody conveniently forgot was that another feature added in the update: built-in gear indicator, which 11-16 N1k's did not have. One of the biggest sins in systems diagnostics is jumping to conclusions based on unproven assumptions. This here is a perfect case of that.

If we just go by exactly what the fault code says, plus the symptom of gear position indicator going blank, along with the modifications that initiated the fault, the most logical explanation is that the gearing ratio changes caused the ECU to become unable to calculate gear position. That is the extent, to which we can derive with any certainty. Everything else is an assumption. Exactly where/how does it says the TC and ABS no longer operate? Where/what literature detailed the 6-axis IMU as the definitive culprit that cause the alleged TC&ABS failure, if the failure(s) actually exist?

N1k prior to '17 also have 3-mode TC and ABS, both of which also take in F&R wheel speeds as primary feedback variables as input into their respective control loops. Yet riders have done all manners of sprocket changes (some far wilder than the 16T and/or 39T in question here), all apparently - and road proven - to no ill effect. How is that possible?

A lesson taught early in Engineering undergrad is "Don't ASSUME, lest you wish to make an *** out of U and ME." ;)
 

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Here some more technical stuff that might be a bit much for some, but in the spirit of the discussion I will throw it out there in case some might find it helpful in understanding the finer points.

Gear shift indicator - this internal calculation is a simple one: engine RPM vs. forward speed. This a a "steady state" function, in that the short moment in between gear changes, no gear position derivation is possible. It is only after the two input variables have achieved stead state that a computation is possible and a result can be declared. This makes the absolute wheel speed important when deriving gear position. The ECU has a particular range of value it is looking for. If a rider changes the gear ratio too much, ECU will not be able to declare a calculated gear position. This is why Service Code 25 also is listed under DFI, Gear Position Sensor. The ECU is letting you know those two sensor values do not reconcile and it doesn't know which might be the problem.

TC & ABS - these control loops are much more concerned about tire slip, which is a value derived from the "transient" behavior of the F&R wheel speeds. That is to say, what happens when the wheel speeds are changing rapidly. When the motorcycle is coasting down a smooth/dry hwy at a steady speed, with no throttle changes, tire slip will be zero or near zero. TC/ABS is monitoring the rate of change of wheel speed at both ends in order to detect abnormal tire slip behavior. This mean TC&ABS are much less concerned about absolute tire speed, and more worried about the pattern of wheel speed delta (rate of change). Therefore, a transient behavior pattern caused by a rear tire losing traction at XX mph will be registered exactly the same, regardless of whether the bike has a 16/39 or 15/41. This must be the case, because TC/ABS works at just about any forward speed and whether the bike is in 1st or 6th gear.
 

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This is the second part of Service Code 25. The fact that this code # references both F&R speed differential and the gear position sensor indicates the ECU cross-references both before displaying gear position readout.

That said, this kind of thing is why I bought the OBDII adapter cable. While the dash only gives the Service Code (25 in this case), OBDII reader should/could provide more detailed DTC (Diagnostic Trouble Code). As of yet, I've not seen anybody post DTCs related to this issue. Might help shed some more light as to what the ECU considers "at fault".

Rectangle Font Parallel Number Diagram
 

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This would be for anyone else who actually trusts the system and doesn't want to change a bunch of baseline calibrations in it without understanding what might be at stake. It might not show up, immediately, or it only shows up when you really need it.
 

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Ok so currently confused lol - too easy to do I know - 2021 N1K I am thinking of adding 2 teeth to the rear and leaving the front? Want to bring cruising revs down a bit as I am doing a lot of highway miles - Or did I get this wrong?
And I assume I will need to do a new chain as well? So might as well do them all? has 7000 kms on the clock so 4500 miles ish
 

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Ok so currently confused lol - too easy to do I know - 2021 N1K I am thinking of adding 2 teeth to the rear and leaving the front? Want to bring cruising revs down a bit as I am doing a lot of highway miles - Or did I get this wrong?
And I assume I will need to do a new chain as well? So might as well do them all? has 7000 kms on the clock so 4500 miles ish
If you want to bring cruising revs down you need to go smaller on the rear sprocket, not bigger.
 

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To try and unconfuse you a bit...this table is for the original 2011 and the gearing has changed just a bit but it will give you a relative notion of rpm/speed. Ignore the speedometer readings. Won't change on our more modern bikes. Also note, a /55 profile tire lowers rpm another 3% as well.
Font Material property Parallel Number Magenta
 
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