Mk3 250 Starting Issues

[Old Cog]

First of all, I'd like to respond as best I'm able to some of Bob's many points.

Model Identification
I’m not aware the bike has any model designation in the UK other than Ducati Mk3 250, imported 1969 - 1976. Checking, I find I misled you on the date of mine: it was first registered 1 Jan 1976, not 75 as I said, so made in 74 or maybe 75. (I gather Ducati shipments were occasionally shunted around the world for a while.)

Warning lights
I have three (though Haynes has only two.) The r/h one is red and lights when the ignition is switched on (It flickers a bit but that’s just something loose. I’ll get into the headlamp shell and sort it out soon.) The middle one is green and lights to show that the parking lights are on. The l/h one is white but doesn’t light up at all. As I said, soon.
The red and white are mounted in bezels, the green just a lens in the headlamp shell, so maybe the latter is a mod not found on all models.

Tuned for racing?
The extra plug just sits there behind the oil feed to the valve gear. There's a pic below.
(Ugly: I’ll have little blanking plug made up for when I have the oil feed off.)
Of course, maybe this bike never had twin spark electrics. There’s no guarantee that head - or indeed that engine - hasn’t come from elsewhere. Jon might remember.

New Alternator needed?
No!
Thanks to you - and to Craig - for the reassurance that I can just have the dedicated coil rewound if need be.
By the way, What I meant was just what you thought - that I wanted to set my question apart for emphasis. (I’m more than happy to explain the ways in which quotation marks are used in British English and explore comparison with US usage but it’s going a bit off topic.)

Back to points?
Think I’ll keep my head down out of that one for now!

Plug Gap
You ask, “So just how large do you normally keep your plug-gap set at, anyway ?”
Well normally I set the gap as per manufacturer’s/manual’s instructions. So in this case I started at 0.035in as per Haynes and then took it down to 0.3. Which seems better. In the light of Jon’s advice I’ll try it narrower still.

Plug too hot?
I agree. (The real problem is that for the sort of pottering I want to do, a softer piston would be better.)

Petrol in the oil
I can only hope there’s no damage to the cams/followers. (An odd effect was that the clutch refused to separate. The friction linings had absorbed petrol and swollen up. It squeezed out in a few days.)

6/12 volt electrics
There may be a problem with the charging system. I’ll put them in a separate post, if only for the sake of those searching topics later.

[b]Kick then blip[/b]
You describe it perfectly

[DewCatTea-Bob]

[quote= Jordan ...
" I don't think there's much wrong with points, "

____ In the past (when I still thought nothing-of taking a quick-look at the points to see that their gap is still set about right), I then preferred the contact-points system cuz I knew I could really trust it,, and if the ign.system ever happened to develop any malfunction, it would then be a simple process to trouble-shoot the source of whatever it's issue !!
__ However with the points-setup, tip-top ign.timing-performance would be a fleeting achievement cuz the point-gap setting refuses to remain optimally set ! _ So that's all I really have against the employment of contact-points.



" if only switching a tiny current to trigger an elec ign system. "

____ I'm sure at-least one method could be devised to allow points to trigger some sort of established electronic-ignition circuitry, but what would be the expected advantage of just that ?
__ You've mentioned the CDI.type of ign.spark-creation, but that type of ign.system is not a really great trade-off (with respect to the std.points-ign.setup),, cuz while it does provide a much improved voltage rise-time (that desirably builds-up the HT.spark much quicker, so as to not possibly become bled-away by a fouled-plug), that type of ign.spark generation unfortunately has a vastly reduced spark-time/duration (that's not desired) !
And-so, it ought be preferred to have any plug-fouling issues rather properly addressed, and rather have a type of ign.system which has the best ign.spark-duration for most efficient combustion, instead.


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

____ Sorry I missed seeing this post sooner !
It's disconcerting that new-pages are created every 10-posts (without each of the thread-page's posts being individually numbered so ya'd then know whether to possibly expect any new-post to be found on a next/newly-created thread-page or not.
__ Also, I had been meaning to submit a response-post to Jorden's, sooner as well,, but my internet-connection has been much more inconsistent than usual lately ! _ So I can't make my posts as timely as I'd like.
(My PC is always left-on with a browser-page opened to this w.site [no matter what-else I'm actually occupied with], so if 'DewCatTea-Bob' is not seen logged-in, then my int.connection is likely down. _ [Although this w.site takes an hour to reflect such loss, so it's possible to still see me as logged-in when I may've in-fact already lost connection here nearly an hour previous !] )




[quote= Old Cog ...
" I’m not aware the bike has any model designation in the UK other than Ducati Mk3 250, "

____ I believe it's officially rather : ' 250 Mark 3 ' .



" I misled you on the date of mine: it was first registered 1 Jan 1976, not 75
so made in 74 or maybe 75. "

____ If made in '75,, I could then find it believable that it came stock with a 12v.system, (as I wouldn't know-better).



" The r/h one is red and lights when the ignition is switched on
The l/h one is white but doesn’t light up at all.
The red and white are mounted in bezels, "

____ I suspect that those two indicator-lamps have had their circuit-wiring swapped-around with each-other,, as the red-light ought-to be for the high-beam warning-indicator, and the white-one for the 'GEN' indicator.



" the green just a lens in the headlamp shell, so maybe the latter is a mod not found on all models. "

____ That feature was eliminated from w-c USA.models because the parking-lightbulb in the std.headlamp was lost, due-to employment of sealed-beam type bulbs for the US.market. -



" The extra plug just sits there behind the oil feed to the valve gear. "

____ Have you ever tried running the engine with it ?



" There's a pic below. "

____ Thanks for the close-up picture of the right-side s.plug-installation.



" I’ll have little blanking plug made up for when I have the oil feed off.) "

____ First I ought point-out that that's not actually an oil "feed", but rather an oil 'return-line' !
__ Since your engine will no-doubt run with the extra spark-plug, I'd suggest leaving it.
Otherwise,, with your high-comp.piston, you may rather consider installing a comp.release in that plug-hole location.



" maybe this bike never had twin spark electrics.
Jon might remember. "

____ I for one am left in great anticipation of learning Jon's explanation for how both spark-plugs were fired-up with whatever ign.system(s) had been employed to take advantage of the apparent previous dual-ignition setup !



" I can just have the dedicated coil rewound if need be. "

____ I suppose it might've been possible for your ign.power-coil to've suffered from some zapping (as a result of the HT.sparking-juice ever having been forced to travel that unintended alternative circuit-pathway, [rather than jump the intended plug-gap]),, however it's more likely that your starting-issue is rather due-to overly stretching-out the already sparse ign.spark too far, (by having the plug-gap set excessively wide).



- OFF-Topic ALERT - ...

" What I meant was just what you thought - that I wanted to set my question apart for emphasis. (I’m more than happy to explain the ways in which quotation marks are used in British English and explore comparison with US usage but it’s going a bit off topic.) "

____ It's really too-bad that such discussion is indeed off-topic here, (and really ought remain curtailed that way, however a brief tidbit ought be permissible), as it seems the majority of post-writers need to learn about such punctuation for proper/correct interpretation of all our written-communication, (but I suspect many rather just don't really care much).
__ Like most-all US.Americans, I've no-doubt forgotten some portion of my education on the long established English-wording rules regarding general punctuation, but I only recall that quotation-marks -( " ) are only intended to be used just for 'quoting' wording which was originally stated by another source.
____ For all our post-writing members to be able to emphasize their text-wording (in a number of differed established styles), we have a fair number of varied niche-emphasis options available, for whichever most appropriately emphasizes the post-writer's intended word-meaning.
__ At top of the post-creation page-window, we have option-buttons labeled: B -(bold) ; i -(italics) ; u -(underline), to pick from !
It's my understanding that bold-lettering is for making-sure that such notated-wording is meant to be emphasized as-if read louder with standout importance,, and italic-lettering is meant to cause the reader to especially-consider what such notated-wording might most-likely be meant to actually mean (possibly rather in a somewhat out-of-the-norm fashion),, while the underlining feature-option provides a way to keep a string of words notably highlighted-together apart from the rest of the surrounding wording (so as to help the reader realize that such notated-wording is meant to be somewhat importantly kept rather directly-associated [as compared to any surrounding regular sentence-wording]).
__ And while covering this kind of stuff (concerning the intended meaning of commonly used punctuation-marks), I'll also note that 'apostrophe' marks -( ' ) placed at both ends of a word or phrase, are meant to note that the wording inserted between is 'coined' ('so-to-speak') in that it's meaning supposedly ought-be rather commonly known-of (by regular users of the English-language).
And-also, most everyone ought already realize that parentheses/brackets -( ( ) / [ ] ) are used for containing wording which really doesn't need to be included as a pertinent-part of the rest of the sentence it's found inserted within, but-yet offers side-note detailing which ought be helpful to keep the reader correctly on-track.
__ Then next, there's the use of 'hyphens' -( - ),, besides their commonly accepted use, I-myself also use them for the opposite-effect which a 'comma' is supposed to indicate, so as to insure that the reader realizes that I definitely intend for neighboring words to be directly-associated (rather than leaving the reader having-to assume whether I actually intended so or not). _ Thus making my intended sentence-meaning easier to properly conceive.
____ Hope this helps (everyone) !


" You ask, “So just how large do you normally keep your plug-gap set at, anyway ?” "

____ Your particular 'quotation-marks' are true quotation-marks for actually quoting another's stated wording, (just as you've properly done) !
I'd always be sure to preferably use those type of quotation-marks (whenever called-for), if any of my keyboards provided the option to access such ! _ But unfortunately I've never found such a full quotation-mark option.

\

" Well normally I set the gap as per manufacturer’s/manual’s instructions. So in this case I started at 0.035in as per Haynes and then took it down to 0.3. Which seems better. "

____ Are you sure the Haynes data you found was in specific regards to plug-gaps especially intended for use with DUCATI-type electronic-ign.systems ?
__ It's been since the '70s since I've been well-aware of the particular associated recommended gap-setting, but I think I recall it being unbelievably small between .5~.6mm -(.019~.023").
So your over-sized gap-setting has no-doubt at-least contributed, if not the bottom-line actual-cause of your sparsely-existent spark (and resulting starting-issue).



" In the light of Jon’s advice I’ll try it narrower still. "

____ Better go-ahead & try it nearer .019" !



" I can only hope there’s no damage to the cams/followers. "

____ Even if they got pretty well scored-up, so long as your motor-oil is kept good & undiluted, their working-surfaces will still work as good as new ! - (Although of-course the remaining life-expectancy would be in question.)



" There may be a problem with the charging system. "

____ Don't forget again to report what your rect/reg.unit seems to actually be !



" Kick then blip "

____ The-trick may actually be having the 'knack' of automatically knowing exactly-when to 'blip' and how much.


Duke-Cheers,
DCT-Bob

[Old Cog]

One or two more folk to thank -

Nick, your explanation of why to take the piston just past TDC on compression is plausible. I'll see if I can overcome decades of old habits and give it a go.

Craig thanks for adding your voice to the reassurances that my spark may look feeble but it's probably ok, and that's it's not too big a deal even if it is going wrong.

And to Bruce for eliciting Jon's explanation of how the electronic ignition system is entirely independent of the battery, lights and charging system.

[Jordan]

I've heard reports that using mechanical points to do elec ign triggering works well.
But one gets scolded by commentators!

Let's not compare points within the Kettering system, with points and an electronic ignition.
Of course a Kettering system demands more maintenance because of the big current involved, that causes point erosion. This is not the case when points are use to trigger an electronic system. Instead, we would only have some lightly loaded mechanical bits to wear - the points themselves should last pretty much forever.

I don't think I'd try this with CDI. Wrong type of HT coil, to be easily switchable to the Kettering "keep going" mode.
There are other electronic ignition schemes.

The advantage is that you could get home in the event of trouble with the electronics, by switching them out and using the good old Kettering standby system. What's not to like about that?

Jordan

[Harvey]

I've heard reports that using mechanical points to do elec ign triggering works well.
But one gets scolded by commentators!

Let's not compare points within the Kettering system, with points and an electronic ignition.
Of course a Kettering system demands more maintenance because of the big current involved, that causes point erosion. This is not the case when points are use to trigger an electronic system. Instead, we would only have some lightly loaded mechanical bits to wear - the points themselves should last pretty much forever.

I don't think I'd try this with CDI. Wrong type of HT coil, to be easily switchable to the Kettering "keep going" mode.
There are other electronic ignition schemes.

The advantage is that you could get home in the event of trouble with the electronics, by switching them out and using the good old Kettering standby system. What's not to like about that?

Jordan

I am a bit late to this, but there is a bit of misconception on the way the CDI system works on a Ducati.
I agree with Jordan's description of his trouble in that firing the system without the HT circuit being complete can damage the coil, but it is the secondary winding that is damaged by the open circuit, causing the voltage to rise to short through its own winding insulation, not to the Primary or the high voltage generating coil in the flywheel.

The flywheel generating High voltage coil, can fail by its insulation breaking down to reduce the generated 350 voltage to a less a figure, that happened to Jordan's.

These three coils are not connected together, only the Primary and the Secondary are connected The generating coil in the flywheel charges the capacitor in the ignition unit, that is triggered by a SCR to dump the stored 350V across the coils Primary.
So an open in the Secondary cannot get back down to the Generating coil to damage it.
I also agree with Jordan that you can use the points to trigger the system. The unit on the Ducati CDI is not very strong on triggering.
The Motoplat uses a different uni that seems to work better. The SCR is triggered by a voltage of about 7V which is held on the trigger, So you only need to have the closed points hold this line to ground, opening the points allow the trigger voltage to rise, to produce the spark. It is very reliable and allows you to use the centrifugal advance to set a different advance curve.

[Jordan]

Thanks for the clarification on open circuit damage to the HT, not the charging coil Harvey.
I guess as Bob says, it's just failure of inadequate wire insulation on the charging coil. The wire is really very fine.

And, I hadn't thought points could be used to trigger a CDI - sounds plausible now that you describe it.
Indeed, you'd need the centrifugal advance mechanism, as you'd lose the inherent advance-retard effect possible with an inductive trigger.

Still, it doesn't protect you from being stuck with no sparks, if the charging coil fails. So if I ever get around to it, I'll be focussing on making an electronic ignition that uses a standard type of HT coil that will also work with Kettering system, using a transistor as the main switch. The points would then just supply a small current to control it.

Jordan

[DewCatTea-Bob]

[quote= Harvey ...
" I am a bit late to this, "

____ Since you've 'quoted' Jordan's post,, it's thusly expected that you must've been referring to merely-just his post alone, when you stated "this". _ However, I suspect that you might've actually meant that you were rather late to this entire thread, (which I'd be more inclined to agree with !). _ But still, it's questionable whether you've read-through this entire thread.



" I agree with Jordan's description of his trouble in that firing the system without the HT circuit being complete can damage the coil, "

____ Since you didn't specify which "coil" you really meant, I'm left to guess (even if I read-through all Jordan's posts again).



" but it is the secondary winding that is damaged by the open circuit, "

____ This is of-course the standardly accepted result as the HT.voltage possibly creates an alternate pathway to ground, as that concentrated high-pressure juice can find the weakest spot in the secondary-insulation and 'zap' it's way through it (leaving a permanent hole-way [that can allow HT.leakage to travel anywhere that best satisfies it !]).



" causing the voltage to rise to short through its own winding insulation, not to the Primary or the high voltage generating coil in the flywheel. "

____ In order to make this conclusion with certain-confidence,, you would've had to've done lab-testing of all the involved stock-type components left set up as normally is, and confirm that the stock setup always results with the very-same abnormal HT.circuit-creation and resulting damage outcome. _ Otherwise it'd be just relying on the standard-deduction that the simplest circuit-route (in the HT.voltage's point of view) ought-to be the normally expected secondary-out to secondary-ground (confined within the ign.coil itself). _ But without actual testing to prove that what's regularly expected is indeed the actual case, it ought-not be concluded that another possible alternate circuit-route isn't simpler for the HT.juice to prefer taking. _ Cuz, (without any testing outcome-results),, we really can't be positively sure that it isn't easier for the HT.voltage/juice to rather zap-through the likely less-resistant insulation-coating of the primary-insulation (of an ign.coil with unknown internal construction-design) (and travel through any [relatively short] electronic circuit-pathways) to end-up also zapping-through the thin insulation of the ign.power-coil to reach the highly-sought goal of 'ground'.
__ However, as I've previously pointed-out in my earlier posts,, I don't necessarily believe that any HT.leakage (leaving the normal confines of the HT.secondary-coil) must actually travel-down (into the alt.stator) to damage the ign.power-coil.
And I really tend-to more-so suspect the same as Harvey has,, that any possible consequential damage resulting from the HT.voltage not being allowed to travel it's normal circuit-pathway, ought most-likely remain confined to the ign.coil-secondary itself.



" The flywheel generating High voltage coil, can fail by its insulation breaking down "

____ So Harvey, what do you suppose could possibly be the blame for that insulation breaking-down (on the alt.stator-located ign.power-coil) ?



" to reduce the generated 350 voltage to a less a figure, "

____ I find it a bit doubtful that the ign.power-coil actually produces any power-pulses with voltages that approach near the supposed 350-volts.
I'd rather expect that many power-pulses (of a lesser voltage, produced between each Otto-cycle) are stepped-up & combined to accumulate a raised voltage near that 350v.amount stored-up within the CDI.capacitor by the time each Otto-cycle finally requires an ign.spark.



" These three coils are not connected together,
So an open in the Secondary cannot get back down to the Generating coil to damage it. "

____ I'm unfamiliar with whatever the actual circuit-design is within the ign.coils (that go-with these stock electronic-ign.systems employed on Duke-models), which may possibly well ensure that any misdirected HT.leakage would confidently indeed remain confined within the ign.coil-body itself. _ But still there might be a possibility for the high current-pressure of 'HT.voltage' to possibly 'zap' itself from the HT.secondary-out to rather circuit through both of the other involved coils (in preference of an overly-excessive spark-gap circuit), regardless of whether they're not directly-connected, (so as to finally reach the HT.secondary-ground destination-point),, as the HT.voltage-juice will always seek whatever happens to be the easiest/less-resistive circuit-route !


Dukaddy-DUKEs,
DCT-Bob

[Old Cog]

Well, Gentlemen, You've certainly taken this discussion way out beyond the scope of my query.
And great stuff it is too.
It occurs to me that this thread now contains a huge amount of very detailed info from incredibly knowledgable experts but the thread title gives no clue. Can anyone edit and archive it so someone looking to explore the alternative ignition systems for a Ducati single would see where to come?

On the practical issue that caused me to start the thread, it seems now that an old, cracking HT lead and a spark plug gap far too big. caused the problem. I've replaced the lead and a week ago I reduced the plug gap down to 0.020in and SO FAR starting - under a variety of conditions - is much improved.
My excuse for setting the gap far too wide to begin with is

plug scan.png

which is from p71 of the Haynes' "Ducati Singles Owners Workshop Manual". (Mind you,the oil capacity is given as 5 Imp pints (2.84 litres) on p63 and 5 litres on p70.

Anyway, many thanks to all who have helped me with this.

[Ventodue]

On the practical issue that caused me to start the thread, it seems now that an old, cracking HT lead and a spark plug gap far too big. caused the problem.

Good stuff - another example of 'Look for the simple solution first'

My excuse for setting the gap far too wide to begin with is ... p71 of the Haynes' "Ducati Singles Owners Workshop Manual".

Ha! That'll learn yer to trust anything in Haynes manual, bar the photos ...

Ciao

Craig