955i Stalls And Won't Start Until Cold

Discussion in 'Technical Help' started by Miles French, Dec 2, 2020.

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  1. Miles French

    Miles French New Member

    Dec 2, 2020
    1
    3
    Brighton UK
    My Sprint 955i (2000) has an intermittent issue that's got me stumped. Yesterday I had a good fast ride for half an hour with no problems, then after a 45 minute stop it fired up immediately again, smooth tickover, no issues, and I rode a more twisty, bumpy route home, about an hour, then just before I got home, I sat at a red light on tick-over (nice and smooth) for about 3-4 minutes, then as I pulled away the engine stumbled and stalled. When I tried to start, the starter whirred energetically, and it fired quite often but never enough to start. Opening the throttle slightly stopped it firing I think. I thought this might be a heat issue or a battery issue so rested it for 10 minutes. Same again. Then after an hour I tried again, and it fired up and ran nicely, but after 5 minutes it seemed inclined to stall on tick-over, and did so once, unless I kept the revs up slightly. It started fine after stalling, and had no other issues on acceleration for example. It did the same thing a month ago, after about 10 minutes riding across town, but it has run perfectly well since then. Both times were after dark so with headlights on. Has anyone had this before? I'd be grateful for any ideas.
     
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  2. Hobnail

    Hobnail Senior Member

    Jan 4, 2020
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    First thing that comes to mind is the stepper motor that regulates idle. Several vacuum hoses in and around the throttle bodies. Check for cracked or leaking hoses. I have a 2000 955i and had similar stalling problems. Traced to rotten rubber hoses. The lovely girl is 20 years old, and funny things can start happening.
     
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  3. Miles French

    Miles French New Member

    Dec 2, 2020
    1
    3
    Brighton UK
    Thanks Hobnail

    I'll check the hoses. It seems erratic but related to heat. I suppose that might open up a leaking hose. I've got a couple of lovely old girls, still just a beautiful but a little cranky from time to time.
     
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  4. ChasChas

    ChasChas Marxist Scum

    Aug 9, 2020
    518
    243
    Kent
    Wouldn't be a bad thing to replace and eliminate anyhow. I'm minded to replace mine before they cause problems. Mine is a youngster at 18 ;)
     
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  5. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
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    Nr Biggar
    Difficult to diagnose but it could be electrical with a failing coil or crank position sensor getting hot. It could be stepper motor, old hoses etc. Your best bet is to eliminate the cheap and easy with vacuum hoses, fuel tank breathers etc., before focusing on electrical issues.
     
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  6. Hobnail

    Hobnail Senior Member

    Jan 4, 2020
    1,245
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    That was my second choice, crank position sensor or perhaps ignition coils, but I have not heard about ignition being an issue previously. However, every day places us in new territory with these gems.
     
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  7. Dartplayer

    Dartplayer Crème de la Crème

    Aug 8, 2018
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    The not starting when hot and ok after cooling does sound like a faulty coil. I lived with one for two years until it failed totally and was so happy to have it replaced
     
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  8. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,445
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    While pretty much all ECU controlled cars have this i am not sure its always used on bikes as only some are water cooled...the ECU coolant temps sensor which gives the ECU feedback on the engine temp and affects fueling delivery IE an auto choke enrichment so when cold more fuel however the default fo a failed sensor is to run the fueling like its a cold engine which causes hot start and idle problems due to over rich mixture....not sure it apply's in this case but worth considering.
     
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  9. Sandi T

    Sandi T It's ride o'clock somewhere!
    Subscriber

    Dec 3, 2018
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    Tucson Arizona
    Happens to the best of us, @Hobnail. ;):joy: I think motorcycle years might be like dog years. Perhaps the algorithm is 1 motorcycle year = 4 human years? Or to be kind, perhaps 1 MC year = 3 human years? I won't divulge my age but, yes, funny things can (and have) started happening. :(:p
     
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  10. Hobnail

    Hobnail Senior Member

    Jan 4, 2020
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    #10 Hobnail, Dec 4, 2020
    Last edited: Dec 4, 2020
    Yeah,
    New chapters, new experiences @Sandi T.
    A few years back the USAF asked us what the fatigue failures will look like in airframes built in the late '50's, (a.k.a. B52). We just smiled and said, "I guess we will find out".
     
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  11. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    Evening all...

    Resurecting an old thread, I know...but similar issue (ish)...

    2002 Speed Triple 955i... Not more than a couple thousand miles on this oil, filter, plugs, air filter (but possibly a good 2 years). New battery.

    Anyhow...I am getting "stalling when warm" issues...

    Restarts fine. Rides fine...but if it gets the opportunity to idle (in traffic) it's a gamble whether she'll stall or not. A throttle blipping keeps her going.

    Looking at the previous replies from last year...I like the idea of eliminating the cheap and easy first!

    I will look at all hoses - fuel tank breathers as well as any others I can find - vacuum hoses round the throttle bodies etc...

    Should these items be split or damaged, are they anything specific to replace with, or just another hose, any hose, of suitable diameter?
     
  12. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,496
    750
    Birmingham
    On my T509 which is an 885 cc version of your bike I used 6mm silicon tubing from ebay but it has to be vacuum quality or it will de form at the bends. You will probably find the old pipes are split at the ends, mine were and the problem was similar to yours.
     
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  13. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire

    Thank you sprintdave!
     
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  14. sikatri

    sikatri Member

    May 23, 2019
    60
    18
    Houston
    Might be the pickup coil is going south. When it heats up it quits working and when the engine cools you can restart. You could test the resistance, but it would test normal when cool. Resistance drops to zero when it heats up. Just a thought.
     
  15. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    Thank you sikatri... My next questions though will be...

    What is the pickup coil?
    Where is it?
    How will I test it?
    o_O

    However, the bike starts fine when warm...it just stalls at idle. Is it likely to be this? It doesn't need to cool down to restart...
     
  16. sikatri

    sikatri Member

    May 23, 2019
    60
    18
    Houston
    #16 sikatri, Nov 2, 2021
    Last edited: Nov 2, 2021
    It’s part of the ignition system. In my Thruxton its under the stator cover. You might need to lookup in a manual how your ignition system is setup. I don’t know how your motorcycle is setup.
     
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  17. DanielB

    DanielB Noble Member

    Jan 13, 2019
    882
    393
    Abingdon, Oxfordshire
    #17 DanielB, Nov 6, 2021
    Last edited: Nov 6, 2021
    *Edit the original corrugated plastic hoses were indeed a little worse for wear. The rubbery ends were split variously and I would be certain, if they are supposed to provide a thorough seal, then they weren't... So, on the assumption that leaky hoses may well be an issue...

    Vacuum hoses replaced with 6mm (internal diameter) silicon hose; will see if this makes a difference at idle...I'll let you know once it's all back together!

    IMG_20211106_160415.jpg

    IMG_20211106_160237.jpg

    IMG_20211106_160223.jpg
     
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