Duke doesn't crank anymore - Page 3 - KTM Duke 390 Forum
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post #21 of 27 Old 12-25-2016, 11:20 AM
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No need to apologize for your excellent English...we foreign-language-deprived Americans envy Europeans for their multilingual abilities.When we use the term "cranking" we mean that the starter motor is operating and turning the crankshaft and piston, even if the engine does not start.

One way you can determine if the starter motor is operational is to bypass the K19 starter relay (I have been incorrectly using the term solenoid) and put 12V electrical current directly onto the +/- terminals on the starter motor if they can be accessed. Of course the engine won't start because you are not energizing the spark plugs or fuel pump but at least that will tell you the condition of the starter motor itself. You can use a car battery for this because the bike's system will only draw the amperage it needs, not the full amperage capacity of the car battery. I'll bet the starter motor turns over which would then indicate a bad relay.

Caveat: I have done this in the past to test solenoids and/or starter motors on cars, but I have to admit that the wiring diagram for this bike in the factory manual is about as inscrutable to me as Egyptian hieroglyphics. In fact I believe they may have copied some of it from inscriptions on the Temple of Luxor. I think I recognize Osiris somewhere in there.
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post #22 of 27 Old 12-28-2016, 05:06 PM Thread Starter
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Quote:
Originally Posted by Mikebet View Post
No need to apologize for your excellent English...we foreign-language-deprived Americans envy Europeans for their multilingual abilities.When we use the term "cranking" we mean that the starter motor is operating and turning the crankshaft and piston, even if the engine does not start.

One way you can determine if the starter motor is operational is to bypass the K19 starter relay (I have been incorrectly using the term solenoid) and put 12V electrical current directly onto the +/- terminals on the starter motor if they can be accessed. Of course the engine won't start because you are not energizing the spark plugs or fuel pump but at least that will tell you the condition of the starter motor itself. You can use a car battery for this because the bike's system will only draw the amperage it needs, not the full amperage capacity of the car battery. I'll bet the starter motor turns over which would then indicate a bad relay.

Caveat: I have done this in the past to test solenoids and/or starter motors on cars, but I have to admit that the wiring diagram for this bike in the factory manual is about as inscrutable to me as Egyptian hieroglyphics. In fact I believe they may have copied some of it from inscriptions on the Temple of Luxor. I think I recognize Osiris somewhere in there.
Haaa thanks, it is good to now that doing my best is enough to be readable

At first Europe is a coalition of countries that doesn't speak the same language so learning foreign one is a need to ensure the internal communication and to develop a worldwide relation. Since English is one of the most used language in the world it seems to be the best option (with Spannish, German and Mandarin). Americans already speak English so the need is different. Thanks for the definition !

You can use a car battery for this because the bike's system will only draw the amperage it needs, not the full amperage capacity of the car battery.
Yeah, you are right. I don't know why I wasn't thinking that way at the moment but anyway thank you for correcting me

I tested the starter motor with 12V potential difference between its terminals and it worked. Since I tested the relay previously (it works too) the conclusion remains the same that is the command circuit of the relay has a low voltage problem. Even if the relay is operational, the command voltage is too low to close the power circuit. Even if the starter is operational too, the current from the battery never flows into it.

I laugh so hard when reading the last part of your message because when reading the diagram last week I taught " this wiring diagram is not easy to decrypt".

Anyway, I am studying my exams so I won't spend more time to look after the problem. I will leave it to a professional by the end of the week. I hope he will find the problem, and of course I will keep you informed if the problem happens for someone else.
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post #23 of 27 Old 01-03-2017, 04:37 PM
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If I may suggest going back to a post early in this thread, double check the condition of the sidestand switch. A while back someone on this board posted about a stalling problem while riding that turned out to be the sidestand switch vibrating slightly and having just a tiny bit of grime on it, combining to just barely making enough contact to kill the engine even though the warning indicator on the dash did not show "Sidestand Down". No check engine light, no other outward sign that there was a problem.
It just so happened that my bike experienced the exact same problem this morning on the way to work; started fine, pulled away from a stop just fine, then while riding in 2nd gear at between 28-31 mph about to shift into 3rd when the engine dies. This happened several times in a row, I tried various gear/speed variables and it was pretty consistent so I figured it must be related to an engine vibe thing (since noone can read their tach while riding!). Sometimes after it stalled it would not crank nor restart, but sometimes it would. Eventually I recalled the thread about the sidestand being dirty, loose and vibrating and reached beneath my engine and wiped the switch with my gloved finger. Boom, bike started immediately and did not so much as sputter on the rest of the ride. I will give it a more thorough inspection when I get home, but its a simple thing to check out before paying a mechanic.

Good luck!
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post #24 of 27 Old 01-04-2017, 10:02 AM
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Maxime, BigShankHank's point is well-taken. The 390's sidestand switch can create a lot of hard-to-diagnose mischief by becoming laden with dirt/chain oil or by vibrating out of range of the magnet. Forum members JohnWayne and Hoover found this very simple and effective mod which cures sidestand issues. I strongly suggest you do this mod to eliminate the sidestand as a present or potential future source of stalling/starting problems.

http://www.ktmduke390forum.com/forum...-stalling.html

That said, I still think you need to investigate why your starter relay command circuit shows only 8-9 volts. A loose, dirty or corroded connection could easily cause such a voltage drop.

Cheers, Will

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1984 Moto Guzzi SP 1000
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post #25 of 27 Old 01-15-2017, 04:27 AM Thread Starter
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Hello everyone

Since I had already given the bike to a specialist I couldn't check the side stand and neither investigate further about the voltage drop.

Anyway, after two weeks the garage called me back. There were two problems:
- The starter button was partially broken and caused a leakage of current to the ground
- There was also a leakage at the rear light which caused a voltage drop as well

For the repair and the maintenance I paid 220 (235$) to an official KTM dealer.

I am glad I put it in the garage because I hadn't taught that the starter button could be broken since I had a voltage when it was pressed. I could have found the leakage at the light by myself I think but not as quick as the garage did.

Anyway, it is ready for the summer and that makes me happy! It is snowy right now so I am not sure I will go for ride.
I really want to thanks everyone for the help, it is really kind of yours!
Thank you!
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post #26 of 27 Old 01-15-2017, 07:32 AM
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Glad that the bike is sorted out and ready to ride, that of course is the ultimate goal.
Have fun!

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post #27 of 27 Old 01-15-2017, 10:54 AM
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If nothing else, Maxime, you learned a lot from this episode about your bike's electrical system and how to troubleshoot it. Helping Duke owners resolve problems is a big part of this forum's role, and I'm happy you were able to find some helpful advice here. Glad your bike is ready to roll when the weather improves.

Bonne route!

Cheers, Will

"If you don't know where you're going, you might wind up somewhere else."
--Yogi Berra

2015 390 Duke
1980 Moto Guzzi V50 II (becoming a cafe racer)
1984 Moto Guzzi SP 1000
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