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Discussion Starter · #1 ·
As title says, I am making a go kart from a Ninja 400 2018 ABS engine I got locally. These are the only parts I purchased:
  • Engine itself (with everything on it)
  • Airbox
  • Harness
  • ECU & Fuse Junction
  • Voltage Rectifier

I'm an engineering student, but I havn't had much experience with engines so I did some reading of the service manual and tried to figure out what I need to plug in to just make the thing turn on. From pages 92-100 I thought that all I needed to plug in was:
  • Throttle Sensor
  • Crankshaft Sensor
  • Gear position Sensor
  • Vehicle Down Sensor
  • Ignition coils
  • Air pressure sensor
  • Fuel Injectors
  • Ignition button thing

Heres the plan I have executed so far:
  • Hook starter motor up direct to battery to see if it works (It did)
  • Plug in the items above
  • hook up the battery
  • Hope that pressing the ignition would start the starter motor through the ECU (I didnt, and this is where Im at now)
  • Put starter fluid in the airbox and see if it turns over (Didnt get here since the ignition doesnt start the starter motor)

So I must be missing something that needs to be plugged in, but after going through the manual I, I thought I plugged in everything thats absolutely required, but clearly im wrong. One of my big problems is that I have the harness but I have no idea what the connectors on the harness go to since they arent labelled and the manuals dont label them.

Here are pictures of everything: Some notes:
  • I ordered proper fuses, temporarily I just shorted them (I know this is bad but I just wanted to test to see if there were problems past the fuses)
  • Pictures show everything thats plugged in and isnt plugged in

Anyways, the help I would really appreciate is:
What do I need to plug in to just make this thing turn on. I dont care about the closed loop mode, since that requires a lot more sensors I dont have, open loop would be just fine.
 

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Other little Ninjas have a security resistor in the ignition keyswitch. If the ignition module/ECU doesn't see that resistor-modified input, it prevents the engine from starting. The wiring diagram in the service manual is vague about it, but it looks like the 400 could still have that.
 
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So, I'm assuming the engine actually works? New oil, can you manually turn it over? Without ALL DFI sensors plugged and grounded, no way it'll start. Do you have a jig to mount this engine and relative parts? That's what sucks about FI. You will at least need the cluster gauge to see the general information about the engine's DFI status. A fuel pump, gas tank, radiator, exhaust is missing. The ABS system is a completely separate entity from the engine's operation, no need to fiddle with that. The vehicle down sensor must be in an upright position. There are other sensors missing, clutch sensor, sidestand switch, without those in their proper state, nos este bien. Am I correct in that you chose this engine because of its incredible raw power and convenient mounting holes? If it's just for fun, then good luck, otherwise I would go with a carbed 250 or similar.
 

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Discussion Starter · #4 ·
So, I'm assuming the engine actually works? New oil, can you manually turn it over? Without ALL DFI sensors plugged and grounded, no way it'll start. Do you have a jig to mount this engine and relative parts? That's what sucks about FI. You will at least need the cluster gauge to see the general information about the engine's DFI status. A fuel pump, gas tank, radiator, exhaust is missing. The ABS system is a completely separate entity from the engine's operation, no need to fiddle with that. The vehicle down sensor must be in an upright position. There are other sensors missing, clutch sensor, sidestand switch, without those in their proper state, nos este bien. Am I correct in that you chose this engine because of its incredible raw power and convenient mounting holes? If it's just for fun, then good luck, otherwise I would go with a carbed 250 or similar.
Thanks for the info! When I read the manual though, there was a section that tells you what happens when certain things arent plugged in. Page 120-122 shows ECU backup modes if things arent connected properly. My understanding was that the ecu would just run the engine in open loop mode instead of oxygen sensor feedback mode if these werent connected. Is this interpretation wrong? From this, I gathered that only a few sensors actually make the thing turn on.
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Yes, for safety reasons, some of these sensors must be in the correct state to start the engine. The sidestand switch must be closed grounded I believe. The transmission must be in neutral, or else the clutch switch must be in the correct state. Water temp sensor is missing also...
 

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Discussion Starter · #6 ·
Ok thanks, ill ground that wire.

Today I am trying to manually start the engine with starter fluid. I am just connecting the starter motor to the battery and putting starter fluid in the throttle body. I hear compression and the motor working, but nothing is happening. I suspect something with my wiring from the alternator or voltage regulator is wrong and is not triggering the spark plugs. The thing I think is wrong is there are 6 Y/BK wires that go to ring connectors that I dont have connected to anything and I would susect given their thickness they have something to do with large power. Does anyone know what those are?
18911
 

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Running in open loop is just gonna confuse the ECU, and when it gets confused bad things will happen. lol, I have no knowledge of what it will actually do, maybe a default AFR or limp status? HOw are you feeding fuel without a connected fuel pump to regulate? Again FI, ECU is confused.

Those 6 Y/BK are all ground leads.
 

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Discussion Starter · #8 ·
Running in open loop is just gonna confuse the ECU, and when it gets confused bad things will happen. lol, I have no knowledge of what it will actually do, maybe a default AFR or limp status? HOw are you feeding fuel without a connected fuel pump to regulate? Again FI, ECU is confused.

Those 6 Y/BK are all ground leads.
I am just using starter fluid to see if it turns over. It seems like theres no spark but not sure how to confirm that. Does the starter motor rotate the alternator too or does the ECU need to be conected for sparks to occur?
 

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Like I said, all sensors, parts need to be connected. ECU won't let it start if it ain't happy. Take a look a the wiring schematic, you'll see all the sensors needed.
 
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Ok thanks, ill ground that wire.

Today I am trying to manually start the engine with starter fluid. I am just connecting the starter motor to the battery and putting starter fluid in the throttle body. I hear compression and the motor working, but nothing is happening. I suspect something with my wiring from the alternator or voltage regulator is wrong and is not triggering the spark plugs. The thing I think is wrong is there are 6 Y/BK wires that go to ring connectors that I dont have connected to anything and I would susect given their thickness they have something to do with large power. Does anyone know what those are?
View attachment 18911
All those black wires are frame grounds AFAIK. You will need those for sure.
 

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The bike may start without some of the emissions sensors, but many of the sensors are absolutely required to be connected, and functioning. If the bike down sensor is not sending the correct signal you will have no fuel pump, or spark. That is just one example. I would guess that you will need 98% of the electrical system just to get it to run. All harness and gauge cluster, kick stand switch, etc etc etc.
 

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Oof...that's a handful of a project. Good luck with that! Probably would've been a lot easier to buy a used 400, check everything and label stuff as you transfer it over to your go-kart, and then sell off everything you don't need afterwards. Could've pretty much ended up with the engine, ECU and wiring harness for free if you got a bike for like $3000, since you could get pretty much all that back from the wheels, frame, forks, fairings, gas tank and headlight.
 

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Building Go Kart from Ninja 400 Engine (Need some help)


I saw the title of this thread and I said “Yes. Yes he certainly does…”.:)

Seriously though, have you spent much time driving a 125cc shifter kart? If you have, and can imagine what yet another ten horsepower is going to feel like, how about just using a something like a YZ250 or CR250R bike engine. It’ll be a lot easier, and lighter, unless you have your heart set on using a 4 stroke.

What sort of frame do you have? Does it have front brakes?

@cu260r6 is looking for a (running) Ninja 400 engine…
 

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2019 Ninja 400 ABS, Pearl Storm Gray
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To get the engine to turn over (i.e., starting motor to spin when start button pressed), I think you need at least:
  • power to the starter solenoid
  • (it goes without saying) all your grounds
  • engine stop switch is in run position
  • gear position sensor indicates neutral or clutch sensor indicates clutch is pulled in
Once you get the starter motor to spin, you will have a few more challenges before you get fuel, spark, and ignition:
  • down sensor must be upright
  • kickstand sensor indicates "kickstand up"
  • if you don't have an actual ignition switch assembly, you need an undocumented security resistor on an undocumented pin to the ECU before you power up and attempt to start (I can help with the details if you don't have an ignition switch -- or I might even have a spare switch...).
This sounds like a super fun project -- I'll be excited to hear how it goes!!!
 

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Discussion Starter · #19 ·
To get the engine to turn over (i.e., starting motor to spin when start button pressed), I think you need at least:
  • power to the starter solenoid
  • (it goes without saying) all your grounds
  • engine stop switch is in run position
  • gear position sensor indicates neutral or clutch sensor indicates clutch is pulled in
Once you get the starter motor to spin, you will have a few more challenges before you get fuel, spark, and ignition:
  • down sensor must be upright
  • kickstand sensor indicates "kickstand up"
  • if you don't have an actual ignition switch assembly, you need an undocumented security resistor on an undocumented pin to the ECU before you power up and attempt to start (I can help with the details if you don't have an ignition switch -- or I might even have a spare switch...).
This sounds like a super fun project -- I'll be excited to hear how it goes!!!
Thanks for the info! I will try the first step! I thought I needed the custer gauge though, and I've been holding off on getting one since its like $250 and not sure if I need it yet. Anyone know?
 

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I'll try disconnecting my meter unit (25031-0765) this weekend and see if the bike still starts -- unless someone already has their body work off and can check more easily -- it looks to just be 3 screws and a connector...
 
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