ignition timing

[3564cam]

Hi,
I have a 1958 125 sport.I have fitted a new 60w electrix alternator and regulator.Can anyone tell me what the ignition timing is please.
regards
Steve

[DewCatTea-Bob]

" I have a 1958 125 sport.
Can anyone tell me what the ignition timing is please. "

____ Sorry, (in 1958 I was then the young proud owner of a 1-year old top-of-the-line fully-loaded Schwinn-Continental bicycle, and then knew nothing of DUCATIs), Ducati-models made much before 1963, are considerably before I became interested in 'cycles'. _ So looks like you need to tell if it had battery-powered ignition or other.
(In any case, I'd expect that about 12-degrees before TDC [static], would be close enough to try it out [in the mean time].)
__ Got any pix of your 125/Duke ?


DUKE-Cheers,
-Bob

[3564cam]

Hi Bob,
the bike is battery ignition.The table in the tech part of this site says static it should be 18-20 degrees with a total advance of 48 degrees.This seems rather a lot but I thought that as I am fitteng a mdern alternator/reg/rec,then do I need so much advance?Some piccies attached for you to see the bike
Regards
Steve

[Jon Pegler]

Fitting a more modern alternator and regulater/rectifier unit will not make any difference to the ignition settings.
48 degrees full advance sounds too much.
Maximum full advance would not need to be much more than 36 degrees.
I would start at 12 degrees static, as Bob suggests.
The auto advance unit that you are using will also affect your timing as different units have different numbers of degrees of advance. Most have either 18 degrees (160 type, probably the 125's too) or 28 degrees for the 250 type advance unit. There are a few other odd advance units with 26 degrees about but I doubt that you have one of those.

Jon

[Bevel bob]

I think i understand your thinking, some mag bikes have wierd timing that appears to be dictated by the needs of the mag rather than the motor, if you have changed to battery ignition a different AAU is needed which has a diferent points cam and timing range.Was your bike a mag ign?. I think the coil is different too.

[DewCatTea-Bob]

____ Thanks for the nice pictures of your fine Duke Steve !
I've never owned or even worked-on one of those 125-OHC models.


" the bike is battery ignition."

____ I realize that with it's new charging-system, you now have no choice but to employ battery-powered type ignition but, are you also meaning to claim that your specific OHC-125 model had battery-type ignition ORIGINALLY as well ?
__ I ask because the engine I'm familiar with that's most similar to yours is the '160-M.Jr', which uses the magneto-type of ignition (as stock on many Duke-models).
__ I understand that the very early DUCATIs used a battery-powered electrical-system not designed entirely by Ducati, so that's my only reason for not concluding that your 125 likely uses the same ignition-type as the 160.
If in any doubt, I'd suggest setting your max.advance ign.timing to be the same as the 160's, and not be too concerned with whatever the static-timing then becomes.
However the ign.advance-unit ought to be checked as being the preferred type for your battery-powered type of ignition-setup.
__ Do you have any pix of the parts which were replaced (by your new charging-system) ?


" The table in the tech part of this site says static it should be 18-20 degrees with a total advance of 48 degrees. "

____ I have never seen that, are you sure ? - (Could the '8' in "48" have possibly been one of those damm zeros with a slash through it ?)


" This seems rather a lot but I thought that as I am fitteng a mdern alternator/reg/rec,then do I need so much advance? "

____ Of course the recommended-setting of the MAX.advance will not at all depend on whatever the charging-system components employed, however I assume your concern about such relationship is due to having 'heard' something about the (static)- advance-timing needing to be less advanced for models converted from "magneto"-type ignition, over to a battery-type ignition. (?)
__ There is indeed an advantage to less STATIC-advance, (for starting purposes), and that can be a possible gain for you, depending on which of the two types of ign.setups you had, before your updated alternator was installed. _ And that's why I had asked you to let me know for sure which type your OHC-125 had before.
__ Besides whatever parts were replaced, can you please also post pix of all the new-parts (from the update-kit) which were installed ?
As you MAY need a different auto.advance-unit, to go with. _ Cuz if you do happen to have the wrong type of points-cam, then whatever you're using for an ignition-coil, will consume too much power & overheat.


Hopeful-Cheers,
-Bob

[Bevel bob]

The AAU has a number stamped on it which will tell what it was designed for, also the cam profile is very different and can be easily compared with a battery ign one.

[3564cam]

Hi all,
Please see the table copied from the tech section on this site.It seems to me that battery-less bikes without AAU have a lot of static advance as they dont have an AAU.The 160 Monza has a battery with AAU and a comutator on the light switch to regulate/balance the current to the battery.It seems my 125Sport is the same as a Monza,same light switch ect.I would like to know why you have to time the rotor on the magneto for bikes with a battery like the 160 but not on a 250 mach 1?What is the relevance of the flywheel position?
Am I right in saying the magneto is AC and behaves like an alternator but still needs to send a charge at the right time to the coil for the spark?All very confusing.
The AAU on the 125 is the same as my Mach 1 so lets assume it has 28 degrees advance,numbers are the same as well.So back to my original question,the table says 18-20 static with 46-48 total at 3000rpm.This figure is the same for larger engined bikes of the same era like a 200 elite but the Mach 1,Monza and GT are 5-8 static with 33-36 at 3000rpm with a 28 degree AAU.Many thanks for any help
Steve

[3564cam]

Hi,
Here are pictures of the Mag/alternator that was on the bike as well as the new one I would like to fit.I have one of these on my Mach 1,350 Desmo and Scrambler with no issues at all.
Regards
Steve

[DewCatTea-Bob]

" It seems to me that battery-less bikes without AAU have a lot of static advance as they dont have an AAU. "

____ Right, the original models to first employ the magneto-like (actually 'Energy-Transfer' !) type of ign.system, were stuck with the static-timing set at the max.advance setting.


" The 160 Monza has a battery with AAU and a comutator on the light switch to regulate/balance the current to the battery. "

____ Wonder where/how you got that notion ? _ While that switch likely does have some effect on how much power is available to charge the battery, it's simply consequential due to the lights sharing the same alt.stator-coil.


" It seems my 125Sport is the same as a Monza,same light switch ect. "

____ Do you mean the "Monza" or the 'Monza Junior' ?


" I would like to know why you have to time the rotor on the magneto for bikes with a battery like the 160 but not on a 250 mach 1? "

____ First off, there's never been a stock-production OHC-Ducati with a complete/real 'magneto' ! _ (Anyone who believes otherwise, please state the location where you think a 'magneto' exits at.)
__ The 160-M.Jr is one Duke-model which makes use of a battery but doesn't employ battery-powered ignition ! _ The Mach-I & others which use battery-ignition are not DEPENDENT on the alternator to allow ignition, since the battery still does the job even if the alternator's power-output happens to be dead at the intended moment/point of ignition, (although that correlated-timing would still be helpful to have occur even so, with such battery-powered ignition models !).


" What is the relevance of the flywheel position? "

__ The rotor of the alternator must be 'timed' -(specifically located to the crankshaft) so that the alternator will then happen to produce near the peak of it's power (of a pulse of DC) at the same moment when the ign.spark is expected to occur, (so that the ign.coil will then be able to become properly energized when it's needed to be). _ Otherwise, the alternator will very likely be caught at some rotation-point when it isn't producing enough power to produce the best ign.spark, (if any at all).


" Am I right in saying the magneto is AC and behaves like an alternator but still needs to send a charge at the right time to the coil for the spark? "

____ Basically, you have the concept,, however it seems that you must be a common-victim of those misinformed who think there's a 'magneto' in the motor... It behaves like an 'alternator' because that's all it really is ! _ It simply provides the required single pulse of DC, (from one of the two DC-pulses of an AC-cycle), to be transferred through the ign.coil whenever the contact-points allows so, (and doesn't itself provide any high-voltage spark-juice, like a real 'magneto' is meant to do !).


" The AAU on the 125 is the same as my Mach 1 so lets assume it has 28 degrees advance,numbers are the same as well. "

____ This confirms my belief that all the very-early DUKEs -(oldest OHC-models) employed only battery-powered type ignition.


" So back to my original question,the table says 18-20 static with 46-48 total at 3000rpm.This figure is the same for larger engined bikes of the same era like a 200 elite "

____ Aside from the 200, I have no personal-knowledge of the recommended ign.timing settings for such older models, so I can't confirm those given on the chart.
However they do seem to be in order, so I'd guess that they're probably correct, but, I would choose to not exceed the 46-degrees max.advance setting ! _ (In fact I'd be less concerned about it, with the max.setting being set no further advanced than 43-degrees BTDC.)


" but the Mach 1,Monza and GT are 5-8 static with 33-36 at 3000rpm with a 28 degree AAU. "

____ So then it's fairly understandable why you have question about this stuff, not seeming to logically 'add-up' as it seems it all actually ought to.
Perhaps someone-else has some alternate theory as to how/why there's such difference, but I think it was simply an updated-effort to help aid in kick-starting and Ducati had something against producing updated-AAUs with more useful/appropriate advance-curves.


Stay-tuned,
-Bob