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Thread: 5 ways of settings idling speed (?)

  1. #1
    apriliaforum newb
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    Question 5 ways of settings idling speed (?)

    Good evening, gentlemen.

    I have recently (about 9 months ago) obtained a Pegaso IE that had a road accident in the past and was left in a garage for about 7 years without starting it. Long story short - after cleaning the injectors and changing the spark plug I managed to start it, then found a new frame (old was wrecked), disassembled the poor bike and put everything together on a new frame with lots of new/used parts. During the whole process I was a frequent guest of this forum group, thanks for the huge database of qualitative answers to good questions.

    And finally I could ride it. It was a woderful feeling, and it stil is. However, I am still having some issues so I will have to spare some more time in the garage with my baby. The biggest issue now is - it sometimes stalls at low RPMs and it is difficult to keep the engine running, unless I keep the throttle open at about 2k RPMs. If it goes lower - engine backfires a few times and stops with such sounds as if something broke inside the engine, but when I start it again it starts and keeps running, if the throttle is opened at about 2k RPMs or higher of course. This mainly happens with cold engine and cold start lever helps (when it is open, engine stops less frequently). But such behaviour can sometimes be noticed even with hot engine, so it is quite difficult to troubleshoot the issue for now. Also, the engine starts quite easily only if I open the throttle, without it the starter needs to get much more turns to finally start the engine, but I want the starter to be working as little as possible. When engine is not stopping suddenly, idling speed is about 1150 RPMs (without cold-start or idling speed cable) with frequent missing burn cycles so it definitely needs adjustment. Also, after starting the engine for the first time when it was assembled, I disassembled the throttle body again to change the injector O-rings and inside the throttle body it was soaking in fuel. Does it mean theres a lot of fuel that does not burn and I should adjust something more than idling speed as well?

    The first thing I wanted to do was to correctly set the idling speed. It was really strange for me to see how many different components on the throttle body are connected with idling RPM so I decided to ask here if I understood everything correctly.

    Here is a photo of IE throttle body (from the manual):

    Click image for larger version. 

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    1. Throttle cable. If I would turn the throttle the cable would change the position of the valve shaft in the throttle body, the potenciometer at the other end of the shaft would change its value and ECU would recognize the change thus sending signals to the injectors to inject more fuel.
    2. If I open the cold start, the cable would change the position of the cold start control lever which would then change the position of the valve shaft in the throttle body and the same as above happens.
    3. and 4. If I screw the factory preset screw (3.) or the idling speed adjusting cable (4.) the position of the valve shaft changes and the same happens.


    Question 1:
    Are these assumptions correct and all 4 methods would yeald the same result? Would the ECU recognize the same outcome if I would keep the throttle turned a bit and locked at the same position or if I would open the cold start lever or if I would screw the idling speed adjusting cable to some point or if I would just change the throttle body potenciometer to a resistor of a correct value? Nothing would change regarding fuel/air ratio?

    Question 2:

    Could someone explain in detail how idling speed should be adjusted via ECU? According to the manual, we should enter the workshop mode with engine turned OFF, ignition switch turned to ON and kill switch turned to ON while coolant tempereature is between 78 C and 94 C:
    Click image for larger version. 

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    Should this procedure really be done with engine OFF? I entered it with engine OFF and tried turning the trimmer on the ECU but without any change on the injection light on the dashboard (after informing me about successful entering to the workshop mode by blinking several times, it stays OFF even when I turn the trimmer). I remember turning the trimmer not more than one full turn clockwise ant one anticlockwise, should I turn it a bit more clockwise to see the light react? When engine is running fine, idling speed is about 1150 RPMs (without cold-start or idling speed cable) so it should be set to a higher value annd it is unclear to me how much the trimmer should be turned clockwise to set a change of about 200 RPMs.

    Also, what would be the indication of the injection light if the RPMs are correct and you enter the workshop mode (and there are no error codes present in the ECU)? Would the light start blinking as soon as you enter the workshop mode, thus indicating the RPMs are correct or it stays OFF at first but starts blinking only when the trimmer position is changed just a bit?


    Question 3:
    Are CO and idling speed adjustment procedures done the same way but difference is that speed is adjusted with engine turned OFF and CO is done with engine ON? I tried entering workshop mode with engine on, but with no success (injection light did not start blinking).

    Question 4:
    After I installed the crash bars I checked them by leaning the bike to the ground so that it would lay on one side. Bars were doing their job and the bike was resting on them perfectly, but the fuel was leaking through one of the (breather?) pipes that go out of the fuel tank:
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    Is this normal? As my bike is going to lay on the ground quite often (because of the terrain I am going to ride) I closed both pipes at the other end. Is this a beef-witted decision which gives the previously mentioned issues with stalling?


    I hope you have come to this point of my post and I would be waiting for your any of your insights.
    Last edited by DrHex; 04-24-2019 at 05:07 AM. Reason: Additional question was added

  2. #2
    apriliaforum Junkie
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    Oh dear. A long post in an age of attention deficit disorder...

    Fortunately I'm of an age where I still prefer to read and understand things, rather than brainlessly follow a youtube video containing so little information (assuming it's actually correct) that I'd rather chew my own leg off than be forced to watch it! I hope you are of a similar mind, because this answer isn't going to be short.

    Firstly yes, you generally understand correctly, but to summarise:

    * The idle adjustment screw without the cable (your number 3) is meant to be a stop for the butterflies such that they don't hit and damage the inside of the throttle bodies. They should never need adjustment and in fact should be sealed by the factory.
    * The idle adjustment screw (4) is for you, the user, to adjust the normal idle speed to around 1400rpm.
    * The throttle cable, as you expect connects to the twistgrip and allows you to open and close the butterflies to vary engine load as needed, and the ECU is kept informed by the TPS on the end of the throttle shaft... AND the MAP sensor mounted in the ECU.
    * The 'cold start' cable is simply a cam which opens the throttle a little to compensate for higher engine friction at starting. It does nothing else; the fuelling is adjusted by the ECU for the start condition and the low operating temperatures (coolant and air).
    * The diagnostic light used when in workshop mode is there to set your engine speed... it is no more use than the tachometer, but it is best to use the indicator light to help diagnose any other issues. I suspect the ECU may capture the TPS output voltage when in this mode, and use it for any offset corrections too, but this just conjecture on my side. Nevertheless, I suggest you use the ECU setting method for the idle speed, just in case.
    * The small screw on the ECU adjusts the idle fuelling, making it slightly leaner or richer by reducing or increasing the injector pulsewidth trim respectively.

    I hope this answers your question 1.

    Question 2 and 3
    Check your MAP sensor hose is OK before you start work, then check and adjust your TPS (pin A-B should be 1.2kOhms). Make sure the engine is fully warm, then stop the engine and enter workshop mode. Then RESTART the engine and adjust your engine speed using the stop screw with the cable (your 4), looking for the change in the flashing light as you've detailed above. Exit workshop mode then check the idle is stable. If it is not, you can try to adjust the trim screw on the ECU. Try 1/4 of a turn and see how the engine responds... in or out it doesn't matter, but I would expect a small increase of idle speed when reducing the fuel trim (anticlockwise) and vice-versa. The point is, you should expect a change of idle speed. If it does not change, maybe there is a problem, for example an air leak in the inlet rubbers. Look and fix the problem before starting again. Eventually you should find a position for the trim screw and the throttle stop screw that gives you a stable idle at 1400rpm. Once you are happy, stop the engine, re-enter workshop mode, restart and re-check the ECU is happy with your idle speed. If not, tweak it until the ECU is happy. If the set speed is already correct, as soon as the engine is restarted, the light should be blinking.

    Question 4
    Hmmm. How can I be polite? I'll just stick with the facts and not make any judgement...
    Your breather hoses MUST be able to breathe. DO NOT close them. However, the two hoses you note are not breathers. One (the front) is a drain for any water that collects around the filler cap, or to prevent fuel flowing on the outside of the tank if you overfill it a little. The other is apparently there to allow you to drain off excess fuel from your tank. Why, I've yet to understand. However, they shouldn't leak fuel when the bike is leant over unless the hose routing is incorrect (or has been shortened), or your fuel cap gasket is damaged.

    Worth noting that some models had the rear hose routed up above the top of the tank, tucked behind the dash, whereas others have it routed down behind the left footrest. I seem to remember the one behind the footrest had a valve or a bung in it... but I cannot remember well. I'll have a look in the parts books for you to see if it is obvious.


    I hope all this helps at least a little.

    Cheers... Paul
    Last edited by tinwelp; 04-25-2019 at 09:05 AM.

  3. #3
    apriliaforum newb
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    Thanks for your non-judgemental and informative responce, Paul. I will check everything you mentioned as soon as my hand is no longer swollen.

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