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Thread: Bike cutting out intermittently

  1. #16
    apriliaforum prov-nov
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    Take a look at your sparkplug caps, I had the same problem and found mine were melted a bit, I plugged my nose and spent the 140 dollars on new ones (no aftermarket option i'm afraid) and it sorted it out, not a problem since

  2. #17
    apriliaforum Member BRG's Avatar
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    Hi drouin955,

    Let me start by suggesting that there are two issues here: one is with the ECU and wiring loom and the other is with fuelling.

    I've been thinking of updating my thread (see post #2) because after another DNF at my first venue in 2011, I had a specialist trace my 'main' problem to pin B36 (power supply) on the ECU motherboard. So, with a replacement ECU and a race wiring loom, I subsequently had 2 venues (149 miles) without any cut-out problems. But then at my last venue, having had a further 67 miles trouble free, the bike started cutting out again...

    I now believe that my latest symptoms (which I think are similar to yours) strongly hint at a fuel starvation issue.

    Background
    My local circuit (run clockwise BTW) is an old aerodrome, so only varies a couple of metres in elevation. It has two identical sets of 60 mph right-left esses and a 40 mph right-left-right bus-stop chicane ('Bybrook'). The rest are medium-to-fast sweeping corners:

    Here's a Google Earth view of the chicane (my line is shown in green):

    Rightly or wrongly, I approach the chicane on the RHS, brake on the limit from ~120mph and use a hefty double-countersteer to get through the complex.

    Symptoms
    On each of the last 3 laps (6 miles), my bike cut out twice in succession on exit the from the chicane (between AX2 and EX3) - always and only at this place. The bike would cut for 0.5-1s, run for 0.5-1s, cut for 0.5-1s then run (Run-Cut-Run-Cut-Run).
    * I held a part-open throttle right through the sequence.
    * I managed to get a look at the clocks while it was happening on one of the laps - the rev-counter stayed active right the way through, the warning triangle did not illuminate nor did any of the other dash lights.
    * When I was pulling into the pits after the end of the session, the fuel low light came on. I managed to siphon 4.5lit out of the tank when I got home.

    Analysis
    After all of the work I've had done on the ECU problem, I want to believe that the new ECU's not at fault.

    I posit that a fierce manoeuvre with low fuel could cause a fuel slew that would result in pump starvation.

    To try to substantiate this, I've taken a few photos of a spare tank that keep in my attic...





    Looking at the inside of the tank, I would say that there is NOT enough space for fuel to surge into as a result of a side-to-side manoeuvre. In contrast, there is a lot of space (and smoothly shelved at that) for fuel to surge forward - for example as a result of harsh braking.

    Could this cause the pump to put a bubble of air into the fuel delivery line? Photos suggest there's about a 2s lag between letting off the brakes and the cut-outs occurring. On average, fuel is being consumed at 0.1cm3/m, so it would be conceivable for such a bubble to cause a cut-out 20-30m later!

    If true, this would explain why, back in 2010, I first had this problem at the chicane (my fiercest braking zone), then later as the fuel level dropped, also at the two esses (my second-fiercest braking zone).

    Also, could the nature of the manoeuvre for this chicane set up resonance in the tank which would cause the subsequent starvation - or is this a posit too far?

    Conclusion
    I therefore conclude (which unfortunately doesn't mean to say that I'm correct) that when hard on the brakes with low fuel, the fuel surges forward and starves the pump.

    If this is the case, the remedy should be a simple (if undesirable) matter of ensuring that the tank is at least half full.

    drouin955, may I ask that you re-examine your symptoms (i.e. fuel level vs. braking intensity) and see if they fit this posit?


    Just in passing, it would seem that the <04 tank shape is different from that of the >=04 (presumably to accommodate the back-of-airbox air filter). Could it be that the earlier tank does not have the shelf I've identified above and so does not suffer the same fuel slew issue? Otherwise one would have expected messrs Haga and Corser to have discovered the problem already!
    BRG
    http://www.zen50505.zen.co.uk/brgw
    '05 Ducati MTS 1000S DS 'Neppomuk' "[...] a nugget of purest green"
    '06 Aprilia RSV 1000 R Factory 'Nibelung'

  3. #18
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    I'm getting this too but less so when I was able to keep positive throttle through the turns. Mine is running very rich but can't figure out why. Someone suggested the ECU detecting a fault and going to the default map to protect the engine, which is on the rich side. I'm still not sure what's going on.

  4. #19
    apriliaforum Junkie drouin955's Avatar
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    Latest update

    First, thank you to everybody contributing info on this, second, I apoligize for my lack of time spent here on the forum, I'm very buzy,with work and any time left is use to ride trackdays.
    Bigthree, I will look into it,for sure, thanks.
    BGR, your symptoms definitively looks very similar to mine(exitting chicane).
    Latest report.: This year I had the opportunity to do many trackdays,at different places and 2 or 3 at each places, to date. Not a single problem all year! (At least in relation to this thread). Bike has been running great all the time. So I can say that I'm fairly confident (I won't bet on this) that the problem is solved. Namely my problems were for the cutting out exitting chicanes related to the tip over switch. It has been secured from moving at all. Second, the other times the bike was cutting out was from the fuel level too low. Now I dont allow the fuel to get any lower than lets say 4 inch from the bottom witch considering the limited space and the space taken by the fuel pump is probably under a liter/quart of fuel left. I now run the bike fairly full to half full and again not once it did cut out on me.
    I do hope other members on this forum can find something in this that can help them.
    Feel free to let this thread live, I will try to keep an eye on it.

  5. #20
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    Quote Originally Posted by drouin955 View Post
    Namely my problems were for the cutting out exitting chicanes related to the tip over switch. It has been secured from moving at all.
    You sure that's a good idea? If you have an off, the engine could end up killing itself from oil starvation or, worse yet, the rear tire is touching you and spinning away on you like a belt sander. I've seen some nasty injuries from that.

  6. #21
    apriliaforum Junkie drouin955's Avatar
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    Quote Originally Posted by Rugbydawg13 View Post
    You sure that's a good idea? If you have an off, the engine could end up killing itself from oil starvation or, worse yet, the rear tire is touching you and spinning away on you like a belt sander. I've seen some nasty injuries from that.
    I know it's a double edge sword, that could possibly ruin the engine. Most bikes didnt have this a few years ago. I just hope the trottle does'nt get stuck!
    On the other hand, getting rammed from behind, because the bike suddently quit had me nervous as it could end up in 2 peoples getting down.

  7. #22
    apriliaforum expert TimeBandit's Avatar
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    Quote Originally Posted by BRG View Post
    ....
    Could this cause the pump to put a bubble of air into the fuel delivery line? Photos suggest there's about a 2s lag between letting off the brakes and the cut-outs occurring. On average, fuel is being consumed at 0.1cm3/m, so it would be conceivable for such a bubble to cause a cut-out 20-30m later!
    ....
    I therefore conclude (which unfortunately doesn't mean to say that I'm correct) that when hard on the brakes with low fuel, the fuel surges forward and starves the pump.
    ....
    I have to say that sounds very very plausible. And it may not be a "bubble" in the line per say, all it might take is that the pump's suction impellers become air-bound temporarily and the whole fuel line instantly looses it's high pressure to the FI nozzles. That 2s lag might be the bleed-down time the line looses complete pressure. I'm with you - just wildly guessing...

    Now this has me wondering... forgive me - thinking out loud again ... with all the sensors on this bike, does the ECU specifically monitor the high-pressure side of the fuel line?? If not, how hard would it be to splice/pigtail a manual PSI gauge from that line? It doesn't seem too difficult to fab up and swap-in a replacement dianostic line with a gauge attached.

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