Engine dying on acceleration

[po18guy]

16 hours ago, MontGuzzi said:

Thanks for the input all.  I have a little more data after my ride home tonight.  It died again on me and wouldn’t even turn over.  I toggled the kill switch on and off and it started right up.  I repeated this four more times, spirited acceleration, bike dies, activate and deactivate kill switch, and it started right up.  This seems pretty squarely electrical, but I’m not sure where to start now.  Any suggestions?

Ahh. More info is always good in online diagnostics. The level of amperage that these miniature relays conduct reminds me of the various Chinese electric water kettles. They also use tiny contact points to transmit big current. It works. For awhile. 

[audiomick]

1 minute ago, MontGuzzi said:

So, will this part work in all five positions?  

Yes. Some of the positions only need a four-contact relay, but a five-contact relay works just as well. The extra contact just doesn't have anything to do in those positions.

[audiomick]

Getting back to the relays, look at this:

 

sorry it is a bit messy. I drew it for myself, and wasn't intending to "publish" it.

The drawing is an "extraction" of the parts of the complete circuit diagramme that are relevant to the starter circuit. It is correct for my 2002 Le Mans, and I believe later models also had the same circuitry.

Anyway, you can see that the ECU relay gets the power that activates it after the ignition switch, either the side-stand switch or the relay that is triggered by the neutral switch, and the kill switch.

I had to think about it again myself, but the side-stand switch must be closed when the side-stand is up, and therefore pass current in that positon. If the side-stand is down (switch open), then the neutral switch must be closed (neutral selected) to activate the side-stand switch relay and pass current through there instead of the side-stand switch.

So...

If you can replicate your results from toggling the kill switch by putting the side stand down and then back up, or turning the ignition off and back on, it might point to the ECU relay as your culprit. Doing the same test with the neutral switch would involve putting the side stand down, and putting the gearbox into neutral.

You can see the principle, I hope: switch off and back on the power that triggers the ECU relay by way of various switches, and see if that always brings it back to life. If not, the kill-switch is more likely to be the direct culprit, I think.

I can easily imagine that if the ECU loses power, even for a very short interval, it just goes off, and needs a moment to re-boot before it works again.

I think it is plausible that a dodgy relay might lose contact at higher engine revs (higher/faster vibrations), and regain it after being "cycled". And lose it again when the "critical conditions" re-occur. I would expect, to an extent, that this behaviour might well relate to a resonant frequency related to the internals of the relay in question. That would mean that the behaviour would consistently occur at about the same r.p.m. every time, even when slowly opening the throttle to gradually build up to the engine speed involved. Would you care to experiment a little and see if this may be the case?

If so, that would probably indicate a relay as the culprit, I reckon. Coupled with the apparent relationship with the kill switch, the ECU relay seems likely to me, assuming my speculation is correct. The ECU relay is in position #4, according to my workshop manual.

 

Edited October 10 by audiomick

[MontGuzzi]

8 hours ago, audiomick said:

Would you care to experiment a little and see if this may be the case?

I LIKE it!  I ordered a couple sets of the relays recommended by Docc.  I'll give this a shot tonight. 

Edited October 11 by MontGuzzi

[MontGuzzi]

When I rode home tonight everything worked perfectly.  I can only assume that taking the relays out, putting back in a seating them took care of the corrosion that was on them.  You can see the green corrosion in the photo above.  I was kinda bummed I didn’t get to test @audiomick’s theory, but happyhave have things running properly.  Thanks all!

[po18guy]

39 minutes ago, MontGuzzi said:

When I rode home tonight everything worked perfectly.  I can only assume that taking the relays out, putting back in a seating them took care of the corrosion that was on them.  You can see the green corrosion in the photo above.  I was kinda bummed I didn’t get to test @audiomick’s theory, but happyhave have things running properly.  Thanks all!

"What I did" - Brushed the relay blades, coated them with Caig's DeoxIT. Cleaned the female terminals in the relay box with pipe cleaners and solvent, then the same with a pipe cleaner and DeoxIt. It not only neutralizes and removes corrosion, it leaves a thin protective layer. 

[gstallons]

I still think you will need to repair the kill switch . Since you have stated toggling the kill switch has helped you to restart , I think you will need to clean / repair the contacts in the switch . Kiwi_Roy has (somewhere on this site) a simplified diagram of this circuit . He has at least three diagrams on this site showing 1 Test Point Layout , Simplified Wiring Diagram , Starting Circuit and I am sure there are more . After you look at these and study them , you will be stunned at his knowledge and ability to put this in block diagram w/footnotes ! I printed these off a long time ago so you will need to find them here or I can take pics and e-mail . I did not go over audiomick"s diagram fully to make sure it is absolutely correct and in order . I am certain it should be.  These relays and circuits all interlock so you need to understand what is going on .  

Last year my ExMark mower died and I worked on that through the winter looking at a factory wiring diagram to find out it was the PTO switch not allowing it to crank .  I do not have many good traits . Tenacious is one of them . IDK if it is a good point or a bad point ?

I hate to tell you , you are never gonna appreciate this bike until you FULLY understand this bike !

Edited October 11 by gstallons

[MartyNZ]

11 hours ago, MontGuzzi said:

I ordered a couple sets of the relays recommended by Docc.  

I think that those relays are barely up to the job, and should be regarded as consumables.

I fit new ones at the same time as spark plugs, and I make sure to throw the old ones out, not keep them as spares. Then I put a set of new spares in the monkey paw trap behind the seat.

For a lazy person like me, it's much quicker to change a set of relays than troubleshoot a fault.

[Pressureangle]

5 hours ago, gstallons said:

I still think you will need to repair the kill switch . Since you have stated toggling the kill switch has helped you to restart , I think you will need to clean / repair the contacts in the switch . Kiwi_Roy has (somewhere on this site) a simplified diagram of this circuit . He has at least three diagrams on this site showing 1 Test Point Layout , Simplified Wiring Diagram , Starting Circuit and I am sure there are more . After you look at these and study them , you will be stunned at his knowledge and ability to put this in block diagram w/footnotes ! I printed these off a long time ago so you will need to find them here or I can take pics and e-mail . I did not go over audiomick"s diagram fully to make sure it is absolutely correct and in order . I am certain it should be.  These relays and circuits all interlock so you need to understand what is going on .  

Last year my ExMark mower died and I worked on that through the winter looking at a factory wiring diagram to find out it was the PTO switch not allowing it to crank .  I do not have many good traits . Tenacious is one of them . IDK if it is a good point or a bad point ?

I hate to tell you , you are never gonna appreciate this bike until you FULLY understand this bike !

+1 on the kill switch.

It's possible that a marginal relay resets with a very short cool-down, but I would not expect that to be consistent every time, or in how long it takes to cool. 
But rolling the throttle or hammering the throttle to the pin might hold the clue, that you have a weak kill switch, or possibly a pinched wire grounding to the handlebar. I think it's to be fingered in person, and an inspection with cleaning warranted. 

[gstallons]

On 10/11/2024 at 12:34 AM, MontGuzzi said:

When I rode home tonight everything worked perfectly.  I can only assume that taking the relays out, putting back in a seating them took care of the corrosion that was on them.  You can see the green corrosion in the photo above.  I was kinda bummed I didn’t get to test @audiomick’s theory, but happyhave have things running properly.  Thanks all!

So , you are satisfied and this bike is now running perfectly ?

[MontGuzzi]

Indeed.  It is running perfectly now.  Easy enough to take a peak at the switch, so I will probably do that.  The corrosion on the relays and immediate resolution after reseating them explains the data for me.  I hit all the relays with a contact cleaner.  A friend nice told me that 95% of all electrical problems are bad connections.  Looking backwards a number of decades now, he was right on target!  This is a good prompt for me to go through and clean all of the easily accessed connectors.  

I gotta take the time the to thank everyone on this forum.  Though I’m not particularly active, I would come back here from time to time and always found fantastic, well articulated advice by you(gstallions), docc, mickaudio, and countless others.   I have posted only a handful of times, but that was because most of the answers I sought were addressed in previous posts.  Thanks again, cheers.  

[Tomchri]

And the connectors not easily accessible .

Cheers Tom.

[docc]

1 hour ago, Tomchri said:

And the connectors not easily accessible .

Cheers Tom.

There is this smoke-containment magic (just don't get it on any of the waterproof seals) . . .

[MontGuzzi]

9 hours ago, Tomchri said:

And the connectors not easily accessible

Damn, this is so true—especially compared to my Eldo.  

[docc]