1979 Moto Morini 125H ignition problems.
Posted: Wed Jan 18, 2023 12:30 pm
Rather than continuing to post in the "Veglia revcounter bracket " thread and to keep some sort of order, I hope that this separate thread is acceptable? If not please delete and advise. Thank you.
17/1/2023 themoudie
"My current "Bete noir!" is the Moto Morini 125H ignition problem. This is the same problem as that discussed, with you, by a man named Leonard, before Xmas. Both of us have been driven to distraction by the failure of the flywheel to cause the trigger coil to advance the ignition spark and nobody from the UK MRC, MMOC Netherland, or ignition/electrickery world has been able to come up with a solution. I'm considering a small Ducati engine or alternative could be made to fit. Or, maybe even a stink wheel!
THIS DOES NOT REQUIRE YOUR DIVERSION.
"
17/1/2023 Jordan
"The pickup on Morini uses an inductive coil I think.
As the induced waveform may not be symmetrical, try swapping the two wires."
17/1/2023 themoudie
"Aye Jordan,
Thank you for your suggestion.
Without going into detail the 125H uses a Lambretta/Vespa type flywheel ignition, within the generator rotor. Yes, the trigger coil is inductive and is supposed to produce a full waveform. This was part of my problem, because mine didn't produce a full wave form and therefore didn't advance the ignition. However, since replacing the trigger coil and using 3 different trigger coils, there is no ignition advance. All of the other components have been passively and dynamically tested and appear to be functioning correctly. So, it appears that the interaction, or lack of it, between the generator rotor and trigger coil appears to be the problem. Ducati Electronnica components greater than 30 years old appear to be the problem and OME replacements are no longer available. At present there are no alternative ignition systems manufactured to replace the OME and having contacted all potential manufacturers and received polite "Not worth the time and effort.", my thoughts are turning to alternative engines!
If your interested in the saga so far, here is the link to the thread on the Morini Riders Club forum: MRC_MM125H_ignition_no_spark!"
18/1/2023 Jordan
"I've noticed on my trusty oscilloscope that trigger coils usually produce a sine type wave, but with the slope on one side being very steep (near vertical), the other a gentle slope. Vertical waves usually don't show up on the display, although they are part of a full waveform.
The gentle slope's steepness increases with rotor speed, and this is how the CDI advances, as the trigger voltage arrives earlier in the cycle.
With wires improperly crossed, the gentle slope is not active, but steep slope is, but it cannot provide the needed variation related to engine speed - so ignition is virtually fixed.
Easy to try changing over the wires.
I'm not saying that's definitely the cause of your woes as some internal CDI circuitry might be faulty."
Bill
17/1/2023 themoudie
"My current "Bete noir!" is the Moto Morini 125H ignition problem. This is the same problem as that discussed, with you, by a man named Leonard, before Xmas. Both of us have been driven to distraction by the failure of the flywheel to cause the trigger coil to advance the ignition spark and nobody from the UK MRC, MMOC Netherland, or ignition/electrickery world has been able to come up with a solution. I'm considering a small Ducati engine or alternative could be made to fit. Or, maybe even a stink wheel!

THIS DOES NOT REQUIRE YOUR DIVERSION.

17/1/2023 Jordan
"The pickup on Morini uses an inductive coil I think.
As the induced waveform may not be symmetrical, try swapping the two wires."
17/1/2023 themoudie
"Aye Jordan,
Thank you for your suggestion.
Without going into detail the 125H uses a Lambretta/Vespa type flywheel ignition, within the generator rotor. Yes, the trigger coil is inductive and is supposed to produce a full waveform. This was part of my problem, because mine didn't produce a full wave form and therefore didn't advance the ignition. However, since replacing the trigger coil and using 3 different trigger coils, there is no ignition advance. All of the other components have been passively and dynamically tested and appear to be functioning correctly. So, it appears that the interaction, or lack of it, between the generator rotor and trigger coil appears to be the problem. Ducati Electronnica components greater than 30 years old appear to be the problem and OME replacements are no longer available. At present there are no alternative ignition systems manufactured to replace the OME and having contacted all potential manufacturers and received polite "Not worth the time and effort.", my thoughts are turning to alternative engines!

If your interested in the saga so far, here is the link to the thread on the Morini Riders Club forum: MRC_MM125H_ignition_no_spark!"
18/1/2023 Jordan
"I've noticed on my trusty oscilloscope that trigger coils usually produce a sine type wave, but with the slope on one side being very steep (near vertical), the other a gentle slope. Vertical waves usually don't show up on the display, although they are part of a full waveform.
The gentle slope's steepness increases with rotor speed, and this is how the CDI advances, as the trigger voltage arrives earlier in the cycle.
With wires improperly crossed, the gentle slope is not active, but steep slope is, but it cannot provide the needed variation related to engine speed - so ignition is virtually fixed.
Easy to try changing over the wires.
I'm not saying that's definitely the cause of your woes as some internal CDI circuitry might be faulty."
Bill