Author Topic: Stalls when warm on a run - won't idle  (Read 1270 times)

Offline bluebossa

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Stalls when warm on a run - won't idle
« on: September 16, 2018, 01:21:17 PM »
Been tweaking and test riding my fresh re-build - it's running pretty well after a full Engine swop and re-build, but once warm and on a run won't settle to idle when coming to a stop for junctions, lights etc. Researched the forum and done a few things already.. need to check Z pipe for cracks I think...

So far I've:

Adjusted and Cleaned Plugs
Adjusted Throttle Position Sensor - 0 at off and clicks, working fine
Adjusted Slow Running and Fast Running when Hot
Timing adjusted - in line with advice on here +3 degrees, pulls well
Throttle bodies synched up with Carb gauges
All connections, earths, connectors clean and greased

Starts straight after it's stalled  but needs revs to keep it going on a run- seems fine cold?

Pulls like a train up to 75 mph - will sit idling fine oncee started and back in the garage - just stalls after the overun and coming to a stop.
So is it something to do with the Airflow meter when moving perhaps?

Any ideas - thanks...
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Offline The Mighty Gryphon

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Re: Stalls when warm on a run - won't idle
« Reply #1 on: September 16, 2018, 01:49:08 PM »
My 1992 K100RS 16V did the same thing.  I never was able to find what the problem was.  The last thing I tried was a new voltage regulator.  Sold it shortly thereafter so no history of whether it helped.  My theory was that the voltage was dropping off and killing the ECU output to the injectors.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #2 on: September 16, 2018, 01:58:09 PM »
My 1992 K100RS 16V did the same thing.  I never was able to find what the problem was.  The last thing I tried was a new voltage regulator.  Sold it shortly thereafter so no history of whether it helped.  My theory was that the voltage was dropping off and killing the ECU output to the injectors.

Quite a few people experienced similar - reading though forum.

I've just checked Z pipe and looks in good condition... it's annoying as first ride on it today was siblime - motorway speeds, bumbling along country lanes, but once warm just kept stalling... makes for a tricky ride...

Everything is 100% tight and clean too... been through every nut, bolt, rubber and connection.
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Offline Chaos

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Re: Stalls when warm on a run - won't idle
« Reply #3 on: September 16, 2018, 02:18:14 PM »
Have you checked the Hall Effect Sensor, you can do it with a hair dryer.  The tend to act up when hot.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #4 on: September 16, 2018, 05:09:41 PM »
Have you checked the Hall Effect Sensor, you can do it with a hair dryer.  The tend to act up when hot.

No, but I've got a spare HES off original Engine, so maybe swop over at the weekend.

I've just had all the Airscrews out and cleaned and reset them.
Starts perfect - and seems great when cold - tiny bit reluctant to get up above 1000 revs at first quarter turn. Ticks over lovely though.

Thanks for tip... will report
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Offline Supershooter

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Re: Stalls when warm on a run - won't idle
« Reply #5 on: September 16, 2018, 10:41:40 PM »
I may be having the same or even a different issue. Starts fine, go for a ride come to a stop sign and the it doesn't wN to get going again, so I'll be watching.

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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #6 on: September 21, 2018, 08:17:08 AM »
Ordered and received a Z Pipe - otherwise known as Crankcase Breather pipe... 10

Took the old one off, fitted and inspected it and though it looked OK when unstressed you can see cracks when it's moved...
While I can't seem to make it leak from my own lungs - who knows, this seems to affect pretty much all K75s and is a weakspot from what I have read.

Started Bike and did seem to idle solidly without any hunting so hope that's the cure - will report once I've been out on it...
Picture attached for reference
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Online Laitch

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Re: Stalls when warm on a run - won't idle
« Reply #7 on: September 21, 2018, 09:38:18 AM »
Took the old one off, fitted and inspected it and though it looked OK when unstressed you can see cracks when it's moved...
While I can't seem to make it leak from my own lungs - who knows, this seems to affect pretty much all K75s and is a weakspot from what I have read.
How did you hook your lungs up to it?
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #8 on: September 21, 2018, 10:59:37 AM »
How did you hook your lungs up to it?

Through the hole at the front of my face :-)

I've just been out and sprayed Carb cleaner down near TB 1 and it's base where it hits the Head - Idle went way down and even stalled so bugger, must be a leak or a poor seal on the TB Rubber.

Is it a case of just getting a new one or can they be taken off and some Gasket Sealer or similar be smeared between it and head to cure leak?
Any tips - or is it just that the rubber hardens and they need replacing?

This part is 30 each new...

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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #9 on: September 21, 2018, 03:07:35 PM »
Answered my own question, took TBs off, ironed out a couple of nodules, then gasket sealed and refitted.

No leaks, a run awaits
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #10 on: September 22, 2018, 10:02:29 AM »
Test rode it this morning and definitely improving but still not 100% - stalled a couple of times, though a lot less...

I took the plugs out and while 1 and 2 are nice and brown, 3 looked wet/fuelly - pics of 2 and 3 attached.
Cleaned, re-gapped and swopped out Plug 3 for a known good one.. any ideas

Couple of Videos uploading to YouTube of running and stalling for any pointers - thanks in advance...
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Offline bluebossa

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Re: Misfire when warm on a run
« Reply #11 on: September 25, 2018, 08:44:10 AM »
Well - I've done a Tank full of riding now and while it's perfect when Cold, on return legs of trips when fully warm it breaks into a slight wobbly misfire - nothing major, just enough to unsettle it when coming down to idle and occasional stalling.

I'm tweaking away, have Balanced TBs, Cured Vacuum Leak, replaced Z Pipe, Changed and Cleaned Gapped Plugs, Adjusted Slow Running, Adjusted Throttle Position Sensor - Checked mixture using Start button when running - no change in revs.

I've also swopped out Hall Effect Sensor - still the same, can't be 2 that are bust?

I'm thinking it's electrical - and one of the leads looks a bit naff and they are from 1991 - so I've ordered a set and a second hand set of coils.. en route
Anything else to iron it out and perfect it?

... otherwise Bike is brilliant, sublime to ride, easy, torquey and everything is working spot on with replacement Engine.

Be great to get some expert thinking on where you think it might be - again perfect when cold and for first 15 miles or so... develops after that and still pulls well, hit's 80mph on Motorway, seems to top out at that, but no fairing so that's probably right..
.
Here's a fresh picture taken with the addition of Mirrors which arrived today and full Paniers - I love the look of the thing now - was originally an RT of course...

Thanks in advance for any ideas?
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Offline KIWIDON

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Re: Stalls when warm on a run - won't idle
« Reply #12 on: September 25, 2018, 05:37:59 PM »
Might be worth swapping nbr 3 injector with nbr 1 or 2, give it a good ride and recheck plugs.
If injector at fault it could have poor spray or dribbling, try cleaning with injector cleaner in tank or DIY with 9v batt/aerosol cleaner.
If fault remains at nbr 3 cylinder try your leads/coil by swapping out nbr 3 with another.
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Offline John Lang

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Re: Stalls when warm on a run - won't idle
« Reply #13 on: September 25, 2018, 06:33:38 PM »
I assume your temperature sensor is OK. Might it cause overly rich mix/flooding by failing to detect that the engine has warmed up? You could test this by pressing the start button while the engine is running and cold, then warm. If the warmed-up engine stutters or quits when the button is pressed, your mixture is too rich and the temp sensor might be faulty. At least I think I have that right.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #14 on: September 26, 2018, 01:30:00 PM »
I assume your temperature sensor is OK. Might it cause overly rich mix/flooding by failing to detect that the engine has warmed up? You could test this by pressing the start button while the engine is running and cold, then warm. If the warmed-up engine stutters or quits when the button is pressed, your mixture is too rich and the temp sensor might be faulty. At least I think I have that right.

Hi John, Thanks - not sure re Temp sensor - could change I guess have another.
When I press the Start button on Idle - it just sits the same, no effect at all... think that's OK?

Thanks
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #15 on: September 26, 2018, 01:31:28 PM »
Might be worth swapping nbr 3 injector with nbr 1 or 2, give it a good ride and recheck plugs.
If injector at fault it could have poor spray or dribbling, try cleaning with injector cleaner in tank or DIY with 9v batt/aerosol cleaner.
If fault remains at nbr 3 cylinder try your leads/coil by swapping out nbr 3 with another.

Thanks Kiwi Don - so you think more Fueling than Ignition from your synopsis... I've put a first go of injector cleaner through - why would it be fine cold, but troublesome when warmed up though if it was an injector?
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Online Laitch

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Re: Stalls when warm on a run - won't idle
« Reply #16 on: September 26, 2018, 01:50:26 PM »
Thanks Kiwi Don - so you think more Fueling than Ignition from your synopsis... I've put a first go of injector cleaner through - why would it be fine cold, but troublesome when warmed up though if it was an injector?
Why would you put a first go on injector cleaner if you aren't convinced an injector is at the root? KiwiDon has recommended quick test methods. Unless espresso and croissants are involved, why linger? :giggles
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Offline John Lang

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Re: Stalls when warm on a run - won't idle
« Reply #17 on: September 26, 2018, 05:17:14 PM »
No effect when start button pressed probably means fuel mixture is fine. Bad temp sensor was a long shot.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #18 on: September 26, 2018, 06:27:12 PM »
Why would you put a first go on injector cleaner if you aren't convinced an injector is at the root? KiwiDon has recommended quick test methods. Unless espresso and croissants are involved, why linger? :giggles

Hey Laitch - I meant I've added a bottle of Redex Injection additive to a Tank of Fuel - just for good measure really - I've not taken or cleaned any injector per se.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #19 on: September 26, 2018, 06:29:12 PM »
No effect when start button pressed probably means fuel mixture is fine. Bad temp sensor was a long shot.

Thanks re mixture - should it not still move revs up a little through enrichment, pressing the button I mean?

Temp sensor kinda makes sense if its behaving differently when hot to me... does the temp sensor alter mixture via the EFI, if so that could account for different running properties - it's lovely when cold...
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Offline John Lang

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Re: Stalls when warm on a run - won't idle
« Reply #20 on: September 26, 2018, 07:10:26 PM »
The temp sensor is one of the sources the EFI uses to determine the length of the injection pulse -- others are air mass, throttle position and RPM. Wisdom picked up on this site (forget who the source was) says:

With your engine warmed up and idling at 1000 rpm press the green starter button. If the mixture is correct the revs should stay the same or rise slightly. If the engine dies the mixture is too rich, if the revs increase significantly it is too lean. Adjustment is made by removing the rubber plug on top of the RHF corner of the air box. You need to insert a 5mm allen key. There are a couple of method for determining the mixture, one is the lean  drop method, just type in lean drop method.

As the problem is temp-related, how about the thermostat? If failed, it keeps the motor cooler than it should be. Seems unlikely to be the cause of stalling when warm but as Sherlock said, "when you have eliminated all other possibilities, that which remains, however unlikely...etc"
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Online Laitch

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Re: Stalls when warm on a run - won't idle
« Reply #21 on: September 26, 2018, 07:34:03 PM »
No effect when start button pressed probably means fuel mixture is fine. Bad temp sensor was a long shot.
Thanks re mixture - should it not still move revs up a little through enrichment, pressing the button I mean?
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #22 on: September 27, 2018, 09:04:38 AM »
The temp sensor is one of the sources the EFI uses to determine the length of the injection pulse -- others are air mass, throttle position and RPM. Wisdom picked up on this site (forget who the source was) says:

With your engine warmed up and idling at 1000 rpm press the green starter button. If the mixture is correct the revs should stay the same or rise slightly. If the engine dies the mixture is too rich, if the revs increase significantly it is too lean. Adjustment is made by removing the rubber plug on top of the RHF corner of the air box. You need to insert a 5mm allen key. There are a couple of method for determining the mixture, one is the lean  drop method, just type in lean drop method.

As the problem is temp-related, how about the thermostat? If failed, it keeps the motor cooler than it should be. Seems unlikely to be the cause of stalling when warm but as Sherlock said, "when you have eliminated all other possibilities, that which remains, however unlikely...etc"

Thanks for the explanation John, still learning and the length of pulse makes sense.
Re Starter Button - sounds like Mixture is fine - don't mess I'm reading...

Re Thermostat - I like that theory too, I've got a temp gauge on it, and it is only getting to about a 1/4 way most of the time, so maybe overcooling... time for a new one like you say... but again don't know how that would affect Running when warm... who knows though...

Beyond that I've got nearly new Plug leads and Coils on the way to try some swapping out for Cylinder 3 - will also swop injectors at the same time to  see if the problem moves...

I'm also going to get the Multimeter out on the Temp sensor and see if it checks out against the troubleshooting starting graph 3,000 ohms at Ambient - down to near 0 at 100 degrees C I think - or roughly that... Hot = No resistance - Cold = Resistance in my simple mind...

Will report and appreciate your thoughts, I'm keen to iron out these last foibles on what is a splendid machine.
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Offline bluebossa

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Re: Stalls when warm on a run - won't idle
« Reply #23 on: September 28, 2018, 12:13:22 PM »
I've got a theory that the third injector is not playing properly, so that when the EFI gets the Temp signal the fuel reduction, this leads to a rumble as not enough fuel it getting into a Hot Engine...

I looked into recon Injectors and found a set - this plus leads and coils should flush it out.

I also took the Bike for a run today and got it up to 8,000 RPM and just touching 85 MPH.... so thoroughly Warm
- I then measured resistance on Pin 10 at the EFI versus ground - which is the Temp Sensor signal - 270 ohms so seems good against the Curve from the starting troubleshooter

I've got a replacement thermostat on the way too, as it doesn't seem to get hot enough for my liking by the gauge.
Would expect it to reach half way, would you agree?
Pic attached
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Online Laitch

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Re: Stalls when warm on a run - won't idle
« Reply #24 on: September 28, 2018, 12:45:18 PM »
I've got a replacement thermostat on the way too, as it doesn't seem to get hot enough for my liking by the gauge.
Would expect it to reach half way, would you agree?
It would reach halfway in a perfect world, perhaps. Gauge condition, sensor condition, coolant quality, and wiring all could have an influence on where the needle registers. I'd expect it to register somewhere in the middle third of the scale. Test your existing thermostat in water brought to a boil to determine when it opens.

If you test your moto after each component installation, we might all gain from the result, instead of using the shotgun approach and replacing everything at once.
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Tags: misfire