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For some background, I picked up this go kart from a dude for $300 claiming to have a running CBR 929 motor on it. Got to the place and checked it out, but had no battery and was certain the motor ran a few months ago. I looked over the motor and no signs of crazy damage and the case was still intact! Bonus! So i paid the guy and got it home, sat for a few months and I'm now messing with it.

I also am familiar with general wrenching and understanding of what certain bikes need to start.

I've also have done research and read forums on here with this issue and nothing is too particular to mine as I have found thus far and I will continue to read more threads about this issue.

In saying so, this is what I've came to thus far with messing with the bike.

The tank has fresh gas in it as well and haven't changed the plugs on it as of yet. I hooked the battery up and turned the ignition key, kill switch is set to run, motor is in neutral while noticing it on the gauges and physically checking the sprocket (No chain is mounted on it yet). Kick stand is in the up position, bank angle sensor is shorted correctly. All the fuses are good and checked.

When all of the switches are on, a relay clicks, but no priming. The servo motor for the exhaust moves a bit then goes back, the air box flap goes up to restrict the flow like normal. The starter button is pressed and cranks over like normal.

Now here is where it gets weird. I have 2 ECU's, one from the guy I bought it from, said it needed an ECU and the one he has is bad (Not sure if true, so I thought I would at least test the one that came with the bike.) I also had purchased one from ebay claiming it works and tested it in a known running bike, which I know it works. So when I plug in the so called "bad ecu", it just clicks and cranks and no fuel pump turns on or anything. When I place the good ecu on, it primes just after I plug it in, let it crank and seemed to have wanted to fire, but didn't after fire up. That's good news! I threw some starter fluid into the air box to get it to run, but I noticed when I went to start it again, the pump didn't prime as it should have. I threw the starter fluid in and it fired up roughly and died, but I it has at least spark from the good ecu. I turn the ignition off, disconnect the battery to reset it, and try it again with the good ecu and it doesn't prime this time. So my question is, would I have a grounding issue for this to happen if I know everything seems to work, but is intermittent? If so, where are the grounds I need to be concerned about? I don't want to go head deep into this project and find out the motor is junk or is going to cost a lot to get running.
 

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im sorry i dont have a lot to offer. :) but my first plan of attack would be go through and clean/inspect the connector points on the wiring harness and apply some dielectric grease to each.

i would just try and be as thorough as possible and start at one end and work my way forward. at least on the cart itll be nice n easy to see and get to each. sometimes on a bike it can be a struggle to put hands on them. :)

recently on my 954 i had the exact same issue, crank but no prime. mine turned out to be a burnt/melted wire within the connector up where the front loom hooked into the main. it was just a single wire that had a bad connection or corrosion, gotten hot and melted the plastic a little and really become dirty. i was lucky enough to just be able to clean it up well and hit with dielectric grease and regain fp prime. it was easy enough to see, yours may not be, if thats the issue.

but i do think thats a good place to start. when mine had this issue i was actually going in to check the relays and fuses when i kinda stumbled onto that wiring harness issue.

the cut off switches are often a point of issue when priming is concerned. the engine cut off switch was never intended to be used regularly as a means to stop the engine. it was intended for emergency use, with the key as the preferred way to stop the engine. however, lots of people use the kill switch and it causes issues.

after the wiring harness id take apart and clean and inspect the kill switch contact points. it can be totally disassembled. its often the cause of a no priming issue.

considering it worked before with the good ecu, id be suspect of the harness wires around the point where the ecu hooks into the loom. kinda sounds like maybe the wiring harness was jostled when you were messing with the ecu's? maybe just turn everything on and go through wiggling and listening. :)

you might get online and download or buy a copy of the service manual. it has some troubleshooting charts and testing procedures that might help.
 

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Discussion Starter #3
im sorry i dont have a lot to offer. :) but my first plan of attack would be go through and clean/inspect the connector points on the wiring harness and apply some dielectric grease to each.

i would just try and be as thorough as possible and start at one end and work my way forward. at least on the cart itll be nice n easy to see and get to each. sometimes on a bike it can be a struggle to put hands on them. :)

recently on my 954 i had the exact same issue, crank but no prime. mine turned out to be a burnt/melted wire within the connector up where the front loom hooked into the main. it was just a single wire that had a bad connection or corrosion, gotten hot and melted the plastic a little and really become dirty. i was lucky enough to just be able to clean it up well and hit with dielectric grease and regain fp prime. it was easy enough to see, yours may not be, if thats the issue.

but i do think thats a good place to start. when mine had this issue i was actually going in to check the relays and fuses when i kinda stumbled onto that wiring harness issue.

the cut off switches are often a point of issue when priming is concerned. the engine cut off switch was never intended to be used regularly as a means to stop the engine. it was intended for emergency use, with the key as the preferred way to stop the engine. however, lots of people use the kill switch and it causes issues.

after the wiring harness id take apart and clean and inspect the kill switch contact points. it can be totally disassembled. its often the cause of a no priming issue.

considering it worked before with the good ecu, id be suspect of the harness wires around the point where the ecu hooks into the loom. kinda sounds like maybe the wiring harness was jostled when you were messing with the ecu's? maybe just turn everything on and go through wiggling and listening. :)

you might get online and download or buy a copy of the service manual. it has some troubleshooting charts and testing procedures that might help.
Thanks for the reply! I have the wiring diagram and was looking through it along with going through this forum for any answers.

I have thus done some messing around with the kart and something strange seems to be happening.
The 2 ecu's I have do both things opposite of one another.

I put ecu 1 in and the bike doesn't prime, but does have the relay click on. I crank it over with all of the requirements to get the bike started (key on, kill switch to run, fuses good, battery full, etc.) and I have spark, but no fuel.
I put ecu 2 in and I have prime, fuel spraying from the injectors and everything working correctly, but when I crank it over with the starter button, I have no spark.

Both times I've taken the fuel rails off along with the spark plugs to physically witness what's going on. When I switched back to ecu, the throttle bodies had fuel in it and it started up for a split second then died due to not having the pump and injectors spraying the fuel.

So, correct me if I'm wrong, but somewhere on this forum, they mentioned to place a 2.2k ohm resistor in line of the pink wire by the ignition key? I haven't done so, but plan on doing it this weekend.
I've also read about the 3.7V diode with the extra power supply I did that with ecu 2 and the bike stayed on when I turned the key to the off position.

Any suggestions?
 

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just a quick q, how much of the 929 wiring have you used? It might be worth checking connection in this junction in the loom...

You can test if you have 12v on the Black/White wires going to the coils and injectors. The injectors and coils are individually earthed by the ECU to trigger the fuel/spark and iirc the cam shaft sensor is used for this (front LH on the cylinder head).

I assume the 2 ECUs are the same, and not one from UK and one from USA or somewhere where there was no HISS, and that you have the keys with the corresponding chip in it if it has HISS?

Some info which might helps is that the pump should run for a second or so when the ignition is switched on, then it stops. this is to prime the fuel rail ready for starting. When the motor cranks the pump should also run. This is controlled by the ECU and triggered from the crank sensor on the RH side of the motor. there is a red connector on this and you can test is a voltage is being generated by the sensor using a multimeter on a low volts setting, its only a few volts it will generate.

I hth you.
 

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Discussion Starter #5
just a quick q, how much of the 929 wiring have you used? It might be worth checking connection in this junction in the loom...

You can test if you have 12v on the Black/White wires going to the coils and injectors. The injectors and coils are individually earthed by the ECU to trigger the fuel/spark and iirc the cam shaft sensor is used for this (front LH on the cylinder head).

I assume the 2 ECUs are the same, and not one from UK and one from USA or somewhere where there was no HISS, and that you have the keys with the corresponding chip in it if it has HISS?

Some info which might helps is that the pump should run for a second or so when the ignition is switched on, then it stops. this is to prime the fuel rail ready for starting. When the motor cranks the pump should also run. This is controlled by the ECU and triggered from the crank sensor on the RH side of the motor. there is a red connector on this and you can test is a voltage is being generated by the sensor using a multimeter on a low volts setting, its only a few volts it will generate.

I hth you.
The whole wiring harness is still intact with some connected cut like the lights and turn signals and such. As far as all of the whole main wiring harness, it seems to be all good. I will check that junction as I was curious on what that junction was prior to all of this happening. For the ecu's, I do only have it sitting on the frame not locked down or anything so I can easily switch between the 2 ecu's. Would those have to be firmly on the frame to ground it out by chance? I'm not sure with the chipped key as it looks to be an off brand one? But if that is the case, wouldn't I be able to bypass that with the diode or the resistor?
What grounds do I need look for?
 

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If you are in the US you’ve not got HISS on a 929.

The pink wire is in addition to the key/chip and is on all models as far as I know.

I don’t think the ecu needs bolting down as it has its own earth wires in the loom. I’ve attached a wiring diagram if it helps.
 

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Discussion Starter #7
If you are in the US you’ve not got HISS on a 929.

The pink wire is in addition to the key/chip and is on all models as far as I know.

I don’t think the ecu needs bolting down as it has its own earth wires in the loom. I’ve attached a wiring diagram if it helps.
Thanks for the diagram and I did find a wiring harness on this forum that helped a lot.
 

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UPDATE:

I have fixed the issue.

So as I mentioned, my symptoms were no spark, but everything else worked as it should. Fuel primed, injectors sprayed, cranked over, had the 9 volts from the pink wire, all fuses were good, all safety switches were either shorted properly or in the correct position. Only thing that was wrong with one of the ECU's was there was no spark. The other ECU had spark, but no fuel prime even though I had the 9 volts coming from the pink wire as needed.

I checked online for this same issue and it kept going to a dead end until I found this video someone posted on YouTube:

I was nervous about busting into the casing of the ecu like he did, but I thought that it's technically not working, so what's the worst that could happen.

I opened up the ECU where he mentioned and found the 2 resistors. I checked them and one was around 10 ohms and the other was within spec of 0.1 ohm. I removed those 2 resistors with the soldering pen and found some 0 ohm, 5% tolerance resistors and put them in series across the 2 outside terminals. Solder those to the board and checked everything once more within the bike for fuses, and grounds shorting etc. Turned on as it should with the prime sound and I had one of the coils hooked to a spark plug on the casing of the motor so I could see if I was getting spark. Sure enough, one small crank and I have a bright nice spark! It actually tried firing on 3 cylinders with the new plugs I had in it! Couldn't have been more excited, plus I saved a gamble and $400 on a used ebay ecu that I wasn't sure had the same issue as this one or not. I purchased a resistor kit on amazon that had the resistors I needed.

Disclaimer: I have also never soldered or have done any type of electrical with the board like this before. It was super easy and could save some serious cha-ching in the long run.

Now the motor runs really good and just have to do some modifications to get it to get it on the road!
 

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^^^

You're a friggin' wizard. Even Harry Friggin' Potter couldn't cast a spell over that thing!

Great result, and one that few of us (meaning me!!) would never even dare to undertake.

If I were to have been faced with such a problem I would have treated it like a former wife. Leave it on the side of the road and get a new one!!:devil :wink
 

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^^^

You're a friggin' wizard. Even Harry Friggin' Potter couldn't cast a spell over that thing!

Great result, and one that few of us (meaning me!!) would never even dare to undertake.

If I were to have been faced with such a problem I would have treated it like a former wife. Leave it on the side of the road and get a new one!!:devil :wink
:laugh :laugh :laugh

If that's the case, send them to me and I'll make those ecu's right!

Whomever posted that video knew what was going on so I commend him for taking on that challenge for sure.
 

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I have read about ECU going bad, and was temped to look inside mine but fixed the issue with needed to. Was the whole circuit board covered in the black gunge or did Honda only seal it at the end where the plug/sockets are?
 

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I have read about ECU going bad, and was temped to look inside mine but fixed the issue with needed to. Was the whole circuit board covered in the black gunge or did Honda only seal it at the end where the plug/sockets are?
It was pretty gunked up in there. I was closest to the plugs though as that is where the resistors are located. I used Klean Strip XYLOL XYLENE solvent to break down the rubber compound. I had some time letting it soak which made the rubber flake off easily. I would cut some down as best as i could, fill the hole with the xylene, let it sit for a few hours at a time and keep picking at it. Just be careful when using a screw driver down there as you really don't know where a lot of the other components are. I just took my time making sure I didn't hit anything I wasn't suppose to.
 

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HTML:
A zero ohm resistor isn't going to be very useful for it's intended purpose (current sensing)!
I would have to beg to differ since I placed 2 of the 0 ohm resistors in place of the ones that were in there originally and it fired right up as it should. The rating for the resistors in the ecu is supposed to be 0.05 of an ohm and the 5% tolerance of the 0 ohm resistor I placed in there takes care of what it needs.I'm not sure if the rating is entirely true, but the guy in the video explained what he did and both have worked. Just expressing what I did!
 

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UPDATE:

I have fixed the issue.

So as I mentioned, my symptoms were no spark, but everything else worked as it should. Fuel primed, injectors sprayed, cranked over, had the 9 volts from the pink wire, all fuses were good, all safety switches were either shorted properly or in the correct position. Only thing that was wrong with one of the ECU's was there was no spark. The other ECU had spark, but no fuel prime even though I had the 9 volts coming from the pink wire as needed.

I checked online for this same issue and it kept going to a dead end until I found this video someone posted on YouTube:

I was nervous about busting into the casing of the ecu like he did, but I thought that it's technically not working, so what's the worst that could happen.

I opened up the ECU where he mentioned and found the 2 resistors. I checked them and one was around 10 ohms and the other was within spec of 0.1 ohm. I removed those 2 resistors with the soldering pen and found some 0 ohm, 5% tolerance resistors and put them in series across the 2 outside terminals. Solder those to the board and checked everything once more within the bike for fuses, and grounds shorting etc. Turned on as it should with the prime sound and I had one of the coils hooked to a spark plug on the casing of the motor so I could see if I was getting spark. Sure enough, one small crank and I have a bright nice spark! It actually tried firing on 3 cylinders with the new plugs I had in it! Couldn't have been more excited, plus I saved a gamble and $400 on a used ebay ecu that I wasn't sure had the same issue as this one or not. I purchased a resistor kit on amazon that had the resistors I needed.

Disclaimer: I have also never soldered or have done any type of electrical with the board like this before. It was super easy and could save some serious cha-ching in the long run.

Now the motor runs really good and just have to do some modifications to get it to get it on the road!
Awesome, it is amazing how you kept the faith in finding a solution. Thanks also to the one who did the Youtube video, must be well equipped when it comes to electrical components. I salute you.
 
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