From: Harold Hallikainen <harold@mai.hallikainen.org>
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Date: Mon, 2 Aug 2021 14:12:12 -0700
Subject: Re: [EE] Honda MT250 ignition waveforms
Thread-Topic: [EE] Honda MT250 ignition waveforms
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> I think you may be mistaken about the magneto wiring. If I recall my old
> Indian motorcycle correctly, it's been a couple of years, the magneto,=C2=
=A0
> coil, and points were all connected in series with the condenser
> connected directly across the points. When the points were closed (most
> of the time) the coil charged. When the points opened the field around
> the coil collapsed causing a high voltage spike for the spark. The
> condenser prevented the points from arcing. You could tell if the
> condenser was the wrong value because one side of the points would pit
> and the other side would build up. Depending on which way it was the
> condenser was either too big or too small.
>
> Allen

Thanks for the comment! It appears Honda did it differently than Indian.
See the schematic at
http://honda-elsinore.alp-sys.com/manuals/MT25074/OwnersManual74mt250.pdf#p=
age=3D80
..

Thanks!

Harold



>
>
> On 8/2/2021 12:58 PM, Harold Hallikainen wrote:
>>> I think the voltages (when points connected) are way too small.  Is
>>> there
>>> a
>>> capacitor (condenser) across the points? it could be broken. Otherwise
>>> there may be another leakage path across the points.  (low oil shut off
>>> or
>>> ignition key??)
>>> I was going to  suggest that the series resistance in the secondary
>>> side
>>> could be high, but the voltage with the points (and ?) disconnected
>>> look
>>> to
>>> be pretty much as I'd expect. I'd expect to see some ringing as well
>>> and
>>> maybe >150V peak if all was going well.
>>> Have you got something else you can compare it to? - even a motor mower
>>> might give you a clue as to what to expect.
>>> RP
>>>
>> Thanks! I think the voltage with the ignition coil is quite low. Note
>> that
>> in this system everything is in parallel. The magneto coil, breaker
>> points, kill switch, capacitor, and the ignition coil primary are all in
>> parallel. Current builds up in the magneto coil with the points shorted
>> as
>> the magnet passes by. Then the points open, and the current goes through
>> the ignition coil primary and the capacitor instead of through the
>> breaker
>> points.
>>
>> My brother had to replace the ignition coil, since it was falling apart.
>> It's possible that the replacement he got was not correct. He got it off
>> a
>> recommendation on a web forum. It may have been incorrect. The service
>> manual on the motorcycle is very unhelpful. It just says to replace
>> everything. I think scope photos of what it should be doing would have
>> been helpful. Especially with the magneto and points driving a specified
>> resistive load.
>>
>> Thanks for the comments thus far!
>>
>> Harold
>>
>>
>>
>>> On Mon, 2 Aug 2021 at 14:03, Harold Hallikainen
>>> <harold@mai.hallikainen.org>
>>> wrote:
>>>
>>>> Thanks for the comments thus far. I've attached some waveforms. I had
>>>> to
>>>> break this into separate emails to stay under the 60 kB limit.
>>>>
>>>> TEK00002 - Edited.png - This is with the ignition coil primary
>>>> disconnected. It is the magneto output with breaker points operating.
>>>> Peak
>>>> voltage is about 40V.
>>>>
>>>>
>>>> Does anyone have any idea of expected waveforms?
>>>>
>>>> Thanks!
>>>>
>>>> Harold
>>>>
>>>>
>>>>
>>>>
>>>>
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