Mk3 250 Starting Issues

[Old Cog]

Hi All

I took the Mk3 out of winter storage a fortnight since and I'm struggling with a couple of issues. Perhaps one at a time/per topic would be best.
The most pressing problem is persuading the engine to fire up. Once running, it's not bad. If I take the plug out and heat it up, the engine will generally start - or at least cough - within 3 or 4 kicks - sometimes sooner. But even that's unpredictable: on the one hand it sat for several months over the winter and then fired up (literally) second kick without any warming of anything; on the other hand, turn it off well warmed up after an hour's run and it may well not start again!
With the plug out, connected and earthed, there is virtually no visible spark, even in very dim light. Maybe every 3 or 4 "kicks" you'll just see a faint flicker. I've tried a new plug, checked connections and ordered new HT lead and cap. But I'm not hopeful.
The bike has a 12 volt conversion and electronic ignition and I only have only the Haynes manual for guidance: the Chapter on electrics is the least informative in the book with none of the data you'd need to check the condition/output of the various electrical components.
I'd be very grateful if someone with relevant experience could give me either any general guidance on what is likely to go wrong with a 12v electronic ignition system or point me towards a source of specs that will let me work through things logically. (By the way, the ignition light stays on even when the engine is running: should it?)

Many thanks for any help available (and if it's not available here then I am in trouble!

[Ventodue]

The bike has a 12 volt conversion and electronic ignition ...

Hi and welcome to the Forum,

Who is the manufacturer of the ignition system? Is it the Ducati Elettrotecnica system or an after market?

Ciao

Craig

[Old Cog]

Hi Craig,

Yes of course, crucial question and unfortunately I'm away from home for a couple of days. But when I'm back I'll take things apart far enough to answer your question.

Oh, and thanks for the welcome

[Nick]

Electronic ignitions often require a healthy battery to function properly. If there is any doubt about your battery, charge it then test it on a load tester or under a proper load, headlight on for a while, etc. Or, better yet, replace it. Check all connections for corrosion, etc.

Of course, if the fuel was not drained prior to parking the bike, the carb should probably be stripped and cleaned.

Whenever a bike won't be ridden again for a while, it's a good idea to turn the fuel off about a 1/2 mile from home and let it use up most of the fuel in the carb. This can save a lot of grief later.

[DewCatTea-Bob]

[quote= Old Cog ...
" Once running, it's not bad.
the engine will generally start - or at least cough - within 3 or 4 kicks "

____ What carb.model does your Duke have mounted ?



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

____ I only know-of one such update-system that provides both an 'electronic-ignition' system combined with a '12v.conversion', and that's made by 'Electrex' (which I've heard-tale has experienced some technical-issues of some sort). _ If you have that particular brand of aftermarket system, then you may care to do a 'search' to check-out what-all has been brought-up concerning it.



" any general guidance on what is likely to go wrong with a 12v electronic ignition system "

____ While I'd expect that there likely exists a 12v.DC-powered electronic-ign.system that could be adapted to a Duke-OHC.single,, most I'm aware-of (such as the Electrex), aren't powered by the battery, but rather by a dedicated power-coil (located within it's associated alternator setup). _ So it would be helpful to determine what type of electronic-ign.system you have, by checking to see if your ign.coil is circuited to battery-power or rather to your alternator.



" the ignition light stays on even when the engine is running: should it? "

____ I assume you're referring to the ('GEN')*indicator-lamp mounted on the top-front of the headlamp, (* which is only found just on wide-case models). _ So if-so,, then yes, that clear-light is supposed to light-up whenever the key-switch allows the battery-power to feed the load-system ! _ So it's not-really solely an "ignition light" (as factory stock),, and considering the fact that your system is-not stock and likely doesn't depend on battery-power to activate your ign.system, that indicator-light probably no-longer has anything at-all to do with the operating-status of your non-original ignition-system.


Hopeful-Cheers,
-Bob

[Jordan]

My own 350 has a Motoplat electronic system, that I fitted new. It's a standard Ducati-supplied part, but installed on an engine that was originally points ignition.
Now, I wouldn't think that an elec ign made quite a few decades ago should have much to compare with a currently made system, but the symptoms you describe are just as I experienced, when the Motoplat failed.
It also became harder to start, with a progressively weaker visible spark, until it no longer fired at all. The diagnosis was a burnt out high voltage coil in the alternator.
The information I got at the time was that such failure can happen, if there is no earth path, or short spark gap, when the engine is kicked over. It's true that, at times I had spun the engine without the spark wire attached to the plug. Apparenty, the hundred of volts that can be generated by the charging coil then take the path of least resistance, which unfortunately was through the winding's insulation, destroying it.
Well, that was the analysis at the time. Could it be that this type of problem still occurs?
Maybe a safety gap should be provided as standard, as on some magnetos.
You could possibly, if only to get you going, put points back in the engine?

Jordan

[DewCatTea-Bob]

[quote= Jordan ...
" I wouldn't think that an elec ign made quite a few decades ago should have much to compare with a currently made system,
the symptoms you describe are just as I experienced,
with a progressively weaker visible spark,
Could it be that this type of problem still occurs? "


____ While the quality & durability of more modern power-winding insulation-coating has probably since been improved somewhat,, it's still fairly likely that as such excess-voltage is allowed to punch holes through the winding-coils' insulation, that the resulting leakage naturally causes the ign.spark to eventually fade-away.
Assuming the diagnosis of a zapped power-coil is actually correct, then what's apt to've occurred in such case when the high-tension spark-juice doesn't have a normally expected circuit-pathway to travel through,, it can then develop enough potential/voltage-pressure to jump-through from the secondary to the primary (internal windings) within the ign.coil, and-then travel back-through the primary-circuitry to the ign.power-coil (within the alt.stator) and there rather easily punch-through the relatively weak insulation-coating to reach ground, thus-then creating a tiny short-circuit (which eventually grows larger) that allows bleeding-off of the primary-voltage that's depended-on to produce at-least the minimum-intensity required for adequate ign.spark.
This is the only feasible scenario that could support the supposed diagnosis of a "burnt*out" power-coil, (* actually having to really mean 'zapped', as it's not possible for such extremely low current to burn/overheat a coil !) _ But I-myself personally harbor doubts about the actual validity of such a diagnosis, and-so really don't support that any such scenario is a real actuality.
__ And in the story-cases of 'Electrex' grief-tales,, I'd suspect that the insulation-coating used by them is probably still also vulnerable to such leakage-malfunction, (and-so likely a main source responsible for most experienced Electrex woes, [and quite-likely certainly-so, if they happened to depend-on questionable coil-insulation that can't even hold-up long-term against the slightly-reduced voltages encountered with normal spark-gapping]).
__ (So now I'm even more inclined to surmise that we're dealing-with the aftermarket-system produced by 'Electrex'. )



" You could possibly,
put points back in the engine? "

____ It ought-to be possible to retain the existing electronic-system's trigger-mechanism to fire another/suited ign.coil rather with power supplied by the battery, (as has been done by 'Dyna-S' points-replacement systems). ...
__ While the reduced primary-voltage (provided by the battery) is certainly-not a possible detrimental operating issue, the-question is whether the internal electronics of the existing electronic-ign.system's black-box can handle the resulting increased current required by an ign.coil with a primary-winding that's made to be powered by merely-just 12-volts.
The existing-system's ign.coil (made to be powered by a pulse of much higher voltage) may still possibly create a visible spark from mere battery-voltage,, but if not a usable spark, then the required use of a std.type 12v.ignition-coil, would possibly have-to have it's primary-circuit current-demand curtailed with a 'ballast-resistor' to help prevent the black-box electronics from becoming overheated.
__ So anyhow, if the internal components of the existing black-box can handle the increased current (that's available from the battery and demanded by the 12v.primary-coil circuit),, then it and the existing trigger-mechanism (in the points & condenser chamber) could continue to effectively retain a form of 'electronic-ignition', (desirably without any need to reinstall the stock ign.points).


Enlightening-Cheers,
DCT-Bob

[Old Cog]

First of all, thank you gents. I've clearly come to the right place.

That said, many of you may not know my model since jimF informs me that the blue and gold Mks was not imported to the US. Maybe one detail mentioned is that the GEN indicator light is not clear but red. There may be other differences.

I find my ignition system is the Ducati Elettrotecnica. Probably installed originally (looking closely at the datesI) but maybe retro-fitted. (There's evidence the engine has been tuned for racing - HC piston and twin plug head - though only one is used.) Haynes largely matches what I've got, and informs me that one of the six alternator coils is isolated from the rest and powers the electronic ignition system - just like Jordan's and the Electrex system Bob describes - so I'm going to assume battery condition/charge is not the issue here. (There is a charging issue, which I'll ask for help with separately.)

So since this is the Ducati kit I assume it's well known to you gents. 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.) The problem Jordan had might well apply, and for the same reason! (If it's really sensitive) and the breakdown of insulation he describes could be going on. Though I can't be sure I quite follow all the pathways Bob describes I think I grasp that the this would not be good news. It's on its way. The big question is, "Does this mean I'm looking at/for a new alternator?"

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

However, 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. I'lI need a week or two - and a bit more practice of my starting technique - before I'll be confident that the ignition on starting is working well enough for now. But it's not a healthy looking spark.

Thanks again. Any further thoughts more than welcome.

[DewCatTea-Bob]

That said, many of you may not know my model since jimF informs me that the blue and gold Mks was not imported to the US. Maybe one detail mentioned is that the GEN indicator light is not clear but red. There may be other differences.

I find my ignition system is the Ducati Elettrotecnica. Probably installed originally (looking closely at the datesI) but maybe retro-fitted. (There's evidence the engine has been tuned for racing - HC piston and twin plug head - though only one is used.) Haynes largely matches what I've got, and informs me that one of the six alternator coils is isolated from the rest and powers the electronic ignition system - just like Jordan's and the Electrex system Bob describes - so I'm going to assume battery condition/charge is not the issue here. (There is a charging issue, which I'll ask for help with separately.)

So since this is the Ducati kit I assume it's well known to you gents. 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.) The problem Jordan had might well apply, and for the same reason! (If it's really sensitive) and the breakdown of insulation he describes could be going on. Though I can't be sure I quite follow all the pathways Bob describes I think I grasp that the this would not be good news. It's on its way. The big question is, "Does this mean I'm looking at/for a new alternator?"

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

However, 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. I'lI need a week or two - and a bit more practice of my starting technique - before I'll be confident that the ignition on starting is working well enough for now. But it's not a healthy looking spark.

____ I, for one,, am now left even-more curious about your particular Duke-model !
Is it indeed a WideCase-model ? _ What model-year is it ? _ What country was it made to be sold within ?
How about posting a picture or two of it ? - (So we can then see for ourselves what carb.model your Duke-engine is having to deal with, [for one thing].)
__ Care to describe your practiced starting-technique (for possible fault-finding) ?


Hopeful-Cheers,
-Bob

[graeme]

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 Desmo's.
Old Cog, my '74 Scrambler and Desmo have the Ducati Electronica ignition. Both have a very weak spark that is hard to see.
But both run well so I haven't bothered to replace the ignition on either.
They are not affected by poor battery voltage as the seperate coil in the stator gives enough to fire both easily.
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.
Both my 450's are testament to the ignition being a good system as they are still going strong since 1974.
I have found that NGK resistor plug caps seem to help the poor spark. Still very weak, but haven't let me down to date.
I use BP7HS plugs "P" for protruding electrode. Maybe this helps get the weak spark closer to the fuel/air charge?

Regards
Graeme