What now? Sputtering, stalling

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by DakarNick, Oct 9, 2012.

  1. DakarNick

    DakarNick Swabee

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    I had planned to take a week off to go from Denver to Hutchinson, Kansas, for an annual Heavy Duty Truck and RV Rally. I didn't make it.

    My 950 started doing "it" again.

    2006 950S
    Emissions crap removed
    Flaperectomy
    Mikuni vacuum pump
    Head2Wind prefilter
    Jets

    Other than that the engine is stock.

    I'd encountered this before. First time was on the way back from FMF June of 2011. It's like it ran out of power. I was climbing Kenosha Pass eastbound with wifey and full bike of camping gear. I made it home and after searching on here I found it was likely my ignition switch.

    I cleaned it and put more dialectric grease on it. It did it again this summer after heading to my parents 45 min away. I cleaned it again and it seemed to be fixed. Until I was halfway from Denver to Kansas.

    Anyway, you don't need a play by play on when it happened this trip so I'll just tell you the symptoms and what I've done so far.

    *Valves checked and shimmed, oil changed, spark plugs replaced 300 miles before trip
    *New battery last year
    *Cleaned ignition switch multiple times on trip
    *Removed and checked Mikuni vacuum pump for oil from crank breather tube. No oil found. Fuel side is clean, also.

    What's happening:

    *Starts and runs fine in neutral, through all RPM ranges.
    *Was running great for the first couple hours. I'd be going along at 70 mph with the throttle holding and my speed would just start dropping slowly. This is on the flats. Giving it more throttle would almost flood it. It would sputter, then if given too much throttle it would die. If I kept off the throttle and got into neutral it would drop to idle and be just fine. If it died it would restart. Then a few miles down the road it would happen again.

    It wasn't hot. It was 28* when I left Sunday morning. Warmed up to maybe 40* by the time I tore the vacuum pump and switch apart on the side of Hwy 83 sixteen miles south of Oakley, KS. Yes, I made the tough decision to backtrack the sixteen miles to Oakley. Of course, it ran fine those sixteen miles. I got a hotel room and called the wife to pick me up. I just couldn't risk it.

    I, stupidly, didn't have a multi-meter with me. So, I'll check the battery today. I don't want to jump to conclusions so I thought I'd post up my problem here.

    Thanks guys.
    #1
  2. DakarNick

    DakarNick Swabee

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    No one even has an idea? This hasn't happened to you? I may actually have time to work on it today.
    #2
  3. EastSideSM

    EastSideSM Isn't that dangerous?

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    Is your clutch slipping? I was on a trip recently and had this happen:

    Bike would seem to hesitate delivery of power when shifting to higher gears. As I made my way the bike was running fine, but eventually I began losing power to the point where the bike was revving in every gear but no forward power being genrated. I had totally cooked my clutch pack. I failed to equate the power delivery loss with clutch slippage and thought instead it was a carburation issue. So I kept riding it.

    Is it possible you are getting some clutch drag, heating up the disks enough to get to the point of slipping lots, but then you stop, they cool and recover enough to get going again, but once you have been under way for some time you start experiencing the power loss?

    Just a thought. I ended up having a leaking master and a hung up backer that contributed to total failure, which happened on the Northway in upsate New York just a few miles from Lake Champlain, at around 9 PM. Goodtimes.
    #3
  4. StmbtDave

    StmbtDave AKA Invisible Dave

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    NIck - I would highly suspect the fuel pump. I have had almost the same symptoms and it was the pump. Geek had a thread that went on for pages as he tried different solutions, insisting that it couldn't be the pump. He finally switched his pump and the problems went away. It's an easy solution.

    Dave
    #4
  5. EastSideSM

    EastSideSM Isn't that dangerous?

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    Or this. However, when I had fuel pump problems, the bike would just die intermittently. But you said you have a mikuni installed? I have only run the OEM mitsubishi pump and am on my third one so I am not sure what happens when the mikuni starts to fail. When my pump was gone, the bike wouldn't run at all.
    #5
  6. DakarNick

    DakarNick Swabee

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    I have the bike apart now. Relocating the Mikuni and pulling vacuum off the rear cylinder instead of the crankcase vent.

    I'll check the clutch, too.

    Thanks guys.
    #6
  7. DakarNick

    DakarNick Swabee

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    I pulled everything to the cylinders. I had to pull it all to unscrew the barb fitting on the rear cyclinder vacuum port.

    I'm going to relocate the Mikuni at the airbox and nix the crankcase breather for vacuum signal.

    I also pulled the clutch pack out. Before I look at everything more in depth, how important is it to put it back as I found it? It IS exactly how I pulled it, but are the clutch disks all the same? Do the teeth need to line up in a specific spot?

    And what do I look for? Burning, hot spots?

    EastsideSM, that does sound like what it's doing. However, it would die while riding after I tried to give it throttle. I never smelled or felt anything like the clutch but who knows.

    Dave, I'm running the Mikuni so symptoms may be different than the electric.

    Thanks guys.
    #7
  8. Joe

    Joe Debaser

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    Fuel filter blockage?
    #8
  9. DakarNick

    DakarNick Swabee

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    I'll be checking both tank lines, petcock, and inline fuel filter this weekend.
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  10. Head2Wind

    Head2Wind MotorcycleMayhem

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    I would check the fuel pressure/delivery of the pump. You should see about 1.5-2.5PSI sustained. Much more than 2.5 PSI and the float needles have a hard time holding. If you still have a OEM pump, I would consider reinstalling it to run the engine with the Mikuni still installed but not connected to the carbs to check static pressure and then open flow over time.
    #10
  11. StmbtDave

    StmbtDave AKA Invisible Dave

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    I forgot you had said you were running the vacuum FP but the symptoms sure sound the same. It just sounds like an intermittent fuel starvation issue.

    Dave
    #11
  12. DakarNick

    DakarNick Swabee

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    I don't have a stock electric pump anymore. I ordered another Mikuni and seal kit. I'll install that and tee in the old one to check it's pressure.
    #12
  13. geometrician

    geometrician let's keep going...

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    yes the clutch needs to be installed as it came out

    look in your engine parts catalog that came with your bike... if you don't have it find one online

    The inner & outermost friction discs are different than those in the rest of the clutch pack.

    also pay attention to the inner spring disc & the cover plate for it. you don't want to get it wrong,

    Sounds like you have fueling issues- could be pump, could be venting (of tanks or carbs)
    #13
  14. StmbtDave

    StmbtDave AKA Invisible Dave

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    So it turned out to be the fuel pump after all :deal. First time I've heard of a Mikuni going bad.

    Dave
    #14
  15. DakarNick

    DakarNick Swabee

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    Wellllllll.... I don't know for sure. I'm blaming the pump for now. I have a new one on order so I'll test the old one.

    If that isn't it then I'm back to square one. However, I am relocating the pump to the airbox for easier access and pulling a vacuum signal off the rear cylinder instead of the crankcase breather.
    #15
  16. TheMuffinMan

    TheMuffinMan Forest Ranger Magnet

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    +1


    My bike had a very similar issue on my long trip last summer. I'd be humming along and then all of the sudden I would loose one cylinder (or rarely both) and it'd start popping sputtering slowing down, and acting like it was on it's death bed :cry. The frequency of the phenomena was related to my speed.

    My pump ended up being fine (stock w/Dr Beans kit) but I had pinched the fuel line out of the main petcock which over time the pump couldn't suck enough fuel through the kink. Once I trimmed the fuel line a bit (I had replaced it earlier with a slightly longer hose to aid in fuel tank removal/replacement) I didn't have any more trouble.


    So to me that sounds like fuel starvation. I'd pursue this first. If I ever get my old stock pump put back together you can use it for troubleshooting.

    You could also check to make sure you carbs are seated in the intake boots. Mine slipped out after 10,000 miles on my trip (but I also didn't tighten the clamps down much since I've stripped out the tiny screws/clamps on the carbs side of the intake boots a couple times). It caused popping and rough running occasionally but didnt cause the bike to die.

    When my ignition contacts were wonky my bike died but the power was still on to the dash/lights and the starter would NOT start the bike again until I cycled the key in the ignition. So I don't think it's your ignition lock contacts.

    It could be your battery contacts/starter relay contacts but I'd expect electrical symptoms which you don't have.
    #16
  17. DakarNick

    DakarNick Swabee

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    Thanks Graham. Sounds like what I was experiencing. Well, at least if it ISN'T the pump, I'll have a spare to take with me on trips. Everything is off the bike now.

    I still have to check tank filters. I'll check the petcock, too, and fuel lines when I reinstall the tanks.

    :clap
    #17
  18. DakarNick

    DakarNick Swabee

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    BUMP! It's doing it again. :cry

    After putting it together last October I never rode it until last weekend. It was depressing and didn't want to mess with it.

    But the weather is getting warmer so I took my wife and myself to dinner last Saturday. Ran fine. Ran fine Wednesday, ran fine this morning. It started to sputter this afternoon just as I pulled into the hobby shop parking lot.

    I had my wife bring the truck by so I could get it home.

    I'll tear it apart this weekend and re-check everything. Blah....
    #18
  19. StmbtDave

    StmbtDave AKA Invisible Dave

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    Aren't these bikes just so much fun to work on? Bay of LA, Baja:

    [​IMG]

    Middle of nowhere = great place for carb problems

    [​IMG]

    I feel your pain...

    Dave
    #19
  20. gefr

    gefr Life is a trip

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    I wonder if you have carb heaters. I experienced carb icing twice. It was damp and humid close to 10C and the bike started sputtering. However if I stopped for a while (say 5') and let it idle, it would clear for another 10 minutes or so. That is why KTM installed carb heaters after 2005 IIRC.
    Cheers
    #20