Mk3 250 Starting Issues

[Old Cog]

Thanks (again) Bob.

Whew!

I've started drafting responses to some of your points but have to give up now. Will complete when I'm able.

Cheers

[DewCatTea-Bob]

[quote= Jordan ...
" Lost me there, Bob. "

____ In like-kind Jordan, I ought likewise mention that you had lost me with your statement: "The diagnosis was a burnt out high voltage coil in the alternator. ", as it's really not possible for the high-voltage/low-current of the ign.coil's 'secondary' to burn the winding-insulation of the ign.power-coil, as there's just no generated heat that could cause such resulting damage. _ So rightly-or-wrongly, I interpreted your stated-wording as actually meaning 'zapped' instead of "burnt out", (since the leaked HT.voltage rather pokes non-visible bullet-holes through any weak insulation !).
__ BTW, I really don't actually personally conceive how the misdirected high-tension voltage-juice (produced by the HT.ignition-coil) could possibly cause any actual harm to the operating-function of the ign.power-coil (down-on the alt.stator.). _ My offered explanation was just the only scenario that could actually possibly validate the damaged power-coil diagnosis you had mentioned, (but, that I came-up with an explanation, doesn't necessarily mean that I really believe the scenario actually leads to any valid malfunction of the power-coil !).



" Both the elec igns fitted standard to Ducati singles have special HT coils, with electronics embedded in with them. "

____ One differing aspect which makes them "special", is that they must have a reduced* turns-ratio (* relative to ordinary ign.coils), since their primary-winding is subjected to already pretty-high voltage to start-out with (for obtaining a sufficient sparking-voltage).
__ I've never taken one of those electronic-type HT.coils apart to see what-all is inside them,, but I'd be far more apt to believe that any electronic-components within, are the more vulnerable weak-link for breakdown due-to misdirected spark-voltage (than is the power-coil) !



" Not so easy to change the coils? "

____ Of-course you're not meaning physically-easy,, and it's duly understandable that I had lost you since I didn't bother to elaborate on how it might be possible to run with a different ign.coil, and-so you're right that it's not so easy as simply swapping ign.coils.



" Battery powered CDI would require a step up transformer, to get the needed 300 or so volts to charge the capacitor. "

____ I had never meant to insinuate that CDI.type electronic-ignition would be involved.
When I indicated that 'electronic-ignition' could possibly remain in use, I had only meant that the trigger-mechanism could continue to replace the function of contact-points.
And as for the involved electronics,, I hadn't yet given that much thought because Graeme had mentioned a 'red-box' which I didn't recall being located anywhere away-from the ign.coil but then hastily-assumed such would contain the related electronics, (as my related/sourced thoughts had actually been carried-over form my previous considerations concerning the Electrex-setup).
I was thinking that it should be possible to have an ignition-setup either like the old AC/energy-transfer or DC/battery-powered ignition-types, except with the points eliminated.



" going back to points shouldn't be so
(extensive?). "

____ I meant that the conversion-work to switch-over to contact-points would be a relatively 'extensive' endeavor compared to what I had in mind. _ But if the involved electronics are unavailably contained within the ign.coil-unit, then the amount of adaptation extensiveness is little different either way.


Enlightened-Cheers,
D.Bob

[Ventodue]

Hi Old Cog,

Tonight I replaced the HT lead and plug cap. Better: still small and bluish but more regular. It MAY be enough to be going on with.

As Graeme said: while the Ducati Elettrotecnica system may not generate a spark that's much to look at, yet it seems adequate to the task ... . (Btw, the system first appeared in 1972).

I find my ignition system is the Ducati Elettrotecnica. Are there any known weaknesses? Are there any tests I can do maybe with the control unit off the bike or of the dedicated alternator coil with the engine running? (I've got a decent multimeter.)

Being largely electronic, the system tends to either work - or not. That said:
a) The resistance of the ignition coil in the alternator should be 350 +/- ohms. (I have seen figures quoted as low as 170 ohms; but all mine are in the 300 range).
b) The pick-up winding can fail, but this tends to be a failure of the 'Instant Death' variety . I had one re-built by West Country Windings.
c) As Graeme said, the transducer box is the same as the 860. When they're blown - and in fact they're generally pretty robust if not abused - replacement is the most practical option, mainly because of the difficulty of de-potting and isolating the components inside.

The big question is, Does this mean I'm looking at/for a new alternator?

Nope. Just get the offending coil re-wound (if it has indeed failed).

Though I'm also interested in Jordan's idea of going back to points. I know where I am with points.

There's really no need to be so radical ...

HTH

Craig

[Jordan]

Though I'm also interested in Jordan's idea of going back to points. I know where I am with points.

There's really no need to be so radical ...

I confess that, having dealt with various elec igns over the years, I have a curiosity about trying a points-triggered version.
Best of both worlds!

Jordan

[DewCatTea-Bob]

[quote= Jordan ...
" I have a curiosity about trying a points-triggered version.
Best of both worlds! "

____ You mean points-triggered CDI.type electronic-ignition ?
Gee Jordon,, I'm afraid to profess that I-myself find such as that combination to rather be the WORST of both ign.system-types ! _ As I'd much,much prefer the stronger/longer-duration ign.spark of a standard points-type ign.system combined with pointsless-triggering !!

Dukaddy-DUKEs,
-Bob

[Jordan]

[quote= Jordan ...
" I have a curiosity about trying a points-triggered version.
Best of both worlds! "

____ You mean points-triggered CDI.type electronic-ignition ?
Gee Jordon,, I'm afraid to profess that I-myself find such as that combination to rather be the WORST of both ign.system-types ! _ As I'd much,much prefer the stronger/longer-duration ign.spark of a standard points-type ign.system combined with pointsless-triggering !!

Dukaddy-DUKEs,
-Bob

I don't think there's much wrong with points, if only switching a tiny current to trigger an elec ign system.
The big attraction is that, with a little extra wiring and a switch, you could select electronic or Kettering (in case of failure).

Jordan

[Jon Pegler]

Old Cog,
I've sent you a PM regarding your 250.
Your 250 has been to Lancaster before, when we took a van full of Ducati singles to the Isle of Man in 1999.

Jon

[ecurbruce]

Here's what I've heard said so far...

Oldcog said;
I find my ignition system is the Ducati Elettrotecnica. Probably installed originally (looking closely at the datesI) but maybe retro-fitted"

And;" The bike has a 12 volt conversion and electronic ignition"

Graeme says;"
Bob, Ducati Electronica were (as far as I'm aware) were fitted to the '74 singles.
The blue and yellow Mk3's, the last Scramblers and the yellow Desmos"

Bob says;"
I'm aware of THAT-fact Graeme, (as I was the top-position employee at a Ducati-dealership back then, and I've owned a '74 450-Scrambler since 1981) ! 
__ What's been keeping me from getting on-track with what we're actually dealing with, is that I've personally been unaware of any stock 250-model (of any model-year) with a 12v.system ! 

and" I'm unaware of any stock Duke-single originally equipped with such an ign.system along-with it's associated alternator being used with a 12-volt system. 
So is your Duke-model newer than 1974, -(the last year singles were imported into the USA) 

Graeme says;"
The red box (I think) is the same as fitted to the 860 twins and had a bad image as being the weak point in the electronic ignition."

Craig says;"
As Graeme said, the transducer box is the same as the 860. When they're blown - and in fact they're generally pretty robust if not abused."

So, here's my question...
Is the elecctrotecnica system fitted to Oldcog's single originally 6 volt or 12 volt? And the "red box" that's the same as fitted to the 860, is it 6 volt or 12 volt?
I wonder what the effect would be converting the 6 volt elecctrotecnica ignition to 12 volt operation, and if it would be able to saturate the ignition coil enough, and would it supply a dwell time long enough at 12 volts  to fire the coil properly?
A 6 volt system would supply higher current, and so would need a shorter dwell, on the other hand a 12 volt system may not supply enough current to saturate the coil at the dwell angle supplied by an electronic ignition system intended to run at 6 volts. Yes, it would function, but not at the at the level the ignition coil now needs at 12 volts.

Bruce.

[Jon Pegler]

The Ducati Electronica electronic ignition system is neither 6 or 12 volts.
The red transducer box is powered at a higher voltage ( I can't remember what exactly) by a dedicated coil on the alternator. The other five coils on the alternator can then be regulated using a standard regulator unit to either 6 or 12 volts, depending on your requirements.
It's often necessary to run both the Ducati and the Motoplat electronic ignition systems with a narrow plug gap (0.020 thou) and time the ignition accordingly due to the weak spark issues.
Not like modern electronic ignition systems that seem to prefer a much wider gap, more like 0.040 thou.
I have used both modern voltage regulators and bridge rectifiers/zener diode combinations in the past to run a 12 volt lighting systems on Ducati singles, whilst still retaining the Ducati Electronica electronic ignition to fire the motor, without any problems.
I can't remember what system I fitted to Old Cogs machine when I used to have it.
Possibly the zener diode route as I did it a long time ago, although it could have been changed subsequently.
I know that there may have been an ignition fault with the bike when it was sold about 5 years ago.
I think it had a replacement transducer fitted at that time, but I could be wrong.

Jon

[DewCatTea-Bob]

[quote= ecurbruce ...
" Here's what I've heard said so far... "

____ After reading-through all your various rounded-up quoted-statements, I had expected to find their summarized bottom-line to perhaps reveal some sort of revelation,, but didn't have anything in particular dawn on me (from that batch of statements alone).
__ It seems that you must've missed one significantly related and relatively important statement made somewhere within this thread though, Bruce,, as I'm pretty-sure that it's been mentioned that the electronic-ign.systems covered within this thread are self-powered and-thus fully functional without any assistance from any battery !



" Is the elecctrotecnica system fitted to Oldcog's single originally 6 volt or 12 volt? "

____ Since we've finally learned that it's a '74-model, we know that it's Ducati electrical-system was originally the standard 6v.system (as most-all stock Duke-singles employ).



" And the "red box" that's the same as fitted to the 860, is it 6 volt or 12 volt? "

____ As Jon has already pointed-out, it's not meant to be specifically powered by either voltage-level.
Rather, it must get-by with the varying AC.voltage supplied by the ign.power-coil alone.



" I wonder what the effect would be converting the 6 volt elecctrotecnica ignition to 12 volt operation, and if it would be able to saturate the ignition coil enough, and would it supply a dwell time long enough at 12 volts  to fire the coil properly?
A 6 volt system would supply higher current, and so would need a shorter dwell, on the other hand a 12 volt system may not supply enough current to saturate the coil at the dwell angle supplied by an electronic ignition system intended to run at 6 volts. Yes, it would function, but not at the at the level the ignition coil now needs at 12 volts. "

____ I think I grasp your concept-thinking on where you suspect a deficiency may've arisen (if the ign.system was meant to be powered by a certain battery-voltage), and that the ign.spark-intensity may've somehow possibly thusly been correspondingly 50%-reduced as a direct-consequence of the 6v to 12v voltage-change.
But-then in order for the spark-juice to've become weakened (and logically/numerically cut-down to near half the normally expected intensity), then the available power-draw of the ign.system would have-to have been limited to the same amount of wattage-consumption as before ! _ But since a battery's available power-juice has no such limited-wattage/power-constraints,, then if the ign.system had depended upon battery-voltage, then the intensity of the ign.spark would've rather doubled instead of being cut-down (with the conversion/switch-over from 6-volts to 12-volts).
__ However (since I really don't actually have a good grasp of your bottom-line reasoning),, I'm thinking that this offered line of reasoning I've given, may be no more relevant to your intended conception-offering, as your offered-reasoning has actually turned-out to be (for in relevant regards to the actually non-battery-powered ign.system under discussion within this thread).


Dukaddy-DUKEs,
-Bob