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Discussion Starter · #1 ·
recently bought a gsx k5 600, the bike so far has changed the spark plugs and fuel pump.

When the bike is hot (103-106ºC is summer here) after more or less 1 hour, from one moment to another it starts to jerk, trying to turn off, being impossible to drive.
At the moment it turns off, "Check" appears and the fuel pump does not start or make a sound until it drops a few degrees, and if you go slowly through the city again it turns off again showing check again and so on until it cools down or take the highway or a route with less heat. (I doubt that it is a temperature problem because if it is hot at the beginning it has no problems)
I really need help because I don't know what else to check

the stator is correct
Replaced fuel pump
The kickstand bypassed
and the emergency stop button too

Thanks a lot
 

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Next time it happens, leave the ignition on, leave the kill switch in the on position. Then remove the front seat and move / wiggle the connectors going to the ECU towards the front and back of the bike. Riding with the seat bolts removed helps to do this quickly before the ECU has time to cool down.

Does that make "CHEC" disappear and the fuel pump prime?
 

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I suspect that what happens is that the connectors and cables of the loom exert a leverage pressure on the circuit board of the ECU. Through vibrations and with this bending force, the copper tracks of the board leading from the connector blocks become stretched and eventually break.
However in "normal" circumstances the copper tracks remain in contact despite being fractured and continuity remains, but when the ECU is subject to excessive heat, the expansion of the board pulls these fractured tracks apart, or alternatively the silicone filler in the ECU becomes softer and allows the board to bend more, and whichever is the heat induced cause, continuity is lost.
This is why the movement of the connectors against that bending force restores continuity, you are forcing those fractured tracks back together.

I still have my defective ECU and would love to try to prove my theory, but I haven't got the time or skill to open it up to investigate. If my theory is correct there is a possibility that the ECU could be repaired with some very careful soldering, which would be the definitive solution because theoretically by swapping the ECU you are possibly just waiting for it to happen again. And buying a used ECU how do you know that it doesn't suffer from this issue? If I sold mine tomorrow, the buyer wouldn't know it is defective until an hour into a ride on a hot summer's day....

I reparied my STVA, but I wouldn't want to try an ECU.
 

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Discussion Starter · #5 ·
ok I'm going to update the topic for the people who helped me.
Thanks above all to @Clipper and @TheGeek since I have done several things throughout these days.

First of all, I couldn't find the solution, the ecu when I was riding the motorcycle was quite hot (probably because it's summer here in Spain and it's about 30 degrees) I couldn't even hold it with my hand.

Second:
I did the test, I changed the ecu with a friend's and it worked, 500km of test and there is no "chec"

Third:
As I have not known why the ecm has died (it could be that it already has 60,000km) I checked the rectifier (regulator) giving me about 14.9 - 15V at idle, which I think is crazy (I clarify that it is the original regulator that already has 20 years)

I changed the regulator and now the new one is giving me values of 13.9 - 14.2V at idle, which seem more normal.

Now my question is:
Can this ecm be repaired?
Has it broken due to mileage?
The Volts are correct giving me the old rectifier ( regulator ) 15V at idle?
Have I done the right thing in buying a new regulator or were those values normal?

I hope you can answer me one more time.
Thank you

And " one pic of my old rectifier"
 

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Glad to hear you have traced the fault, I am not ssurprised that it is ECM related, but it would have been nice to confirm that the failure followed the symptoms expected.

In my case the bike had no other faults, no charging issues, correct voltage at idle and at higher revs, no reg / rec issues. In fact my replacement ECU has been on the bike for a couple of years and the fault has not returned.

By the way, my bike had around 75,000 kms when it started to fail.

I'm going to go out on a limb and say that the reg / rec isssue is not related. I still think that the failures are initially caused by vibrations while the ECU connectors are subject to bending forces from the cables, and that they manifest themselves due to thermal expansion. This would mean that the higher the mileage, the more likely the fault, the more prolonged motorway / high resonation riding, the more likely the fault and the higher the summer temperature, the more likely the fault results in failure.

I think that the ECU could therefore be repaired. I have found a few places to try here in Madrid, but because I bought another, I haven't contacted any of them yet.

Whatever you do, don't pay Spanish breaker yard prices for a "new" ECU, I was getting quotes in excess of 200€, but I bought one off Ebay in the UK for 50 quid.
 

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Corroded connections can also exhibit that kind of symptom. Check all your major connectors for signs of heat or corrosion. Also, buy a cheap multimeter and make it so you can take the seat off quickly. It could be the battery overheating. The trick is to troubleshoot while you're having the symptom.
 

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What did the other side of that connector look like? MIne was melted like that. The heat caused resistance in the wires, and they started to melt. I had to replace wires from stator to reg/rec. And I hardwired the connector at the reg/rec that gets hot. To eliminate to connector.
 
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