ignition timing

[DewCatTea-Bob]

" Here are pictures of the Mag/alternator that was on the bike "

____ That 4-pole dual-coil alt.stator appears to be the correct (& rare) original-type CEV-made unit.
It was made to work with an old/finned-type full-wave rectifier, and the light-switch would also switch-in the extra power-coil (to then help keep the battery charged, with lights running).
__ That very rare alt.stator ought to be worth a pretty-penny to someone !
Can you post a picture of it's matching CEV rotor as well ?


" as well as the new one I would like to fit. "

____ That multi-coil alternator seems to be excessive overkill, unless you also intend to run a high-power headlight.


____ Thanks for the pix !


DUKE-Cheers,
-Bob

[Bevel bob]

I think if this 125 were mine and without any trusted data ,i would set the timing up as per a battery ign 160, when setting the timing up take special care to accurately set the points gap,say 12 thou, then re- adjust to 15thou and check the timing again, you will find a big difference, this is how i make small adjustments to my timing to find the best , a change of even 1 thou is relevant,but it is easy to get back to the base setting if on the road.Moving the points base plate is too unpredictable.With a good charging system and battery the flywheel position is not relevent and probably never was on this bike.

[DewCatTea-Bob]

" i would set the timing up as per a battery ign 160,

____ Copying the 160's recommended max.advance setting is what I also had suggested, however, I know of no 160-models which employed battery-powered ignition, as they all powered their ign.coil directly from one of the alt.stator coil-windings (with yellow wire-lead). _ And the battery in the 160s was only intended for the parking-lights & brake-light & horn !


" With a good charging system and battery the flywheel position is not relevent and probably never was on this bike. "

____ Single-phase alternators with multiple-poles -(like that pictured 12-pole stator has) are probably not worth trying to 'time', so that they're producing max.power-output at the very-moment when the ign.spark is expected. _ However I know I'd want mine properly timed anyhow, so that starting would still be somewhat easier whenever the battery might be too run-down.
__ Four-pole rotors are easier to get adequately timed, and so the alt.power-coil can then really help-out the battery to (timely) provide sufficient voltage for the ign.coil to then produce at least an adequate spark,, as the battery is rarely fully-charged whenever trying to start a cold engine. _ And many of us do realize that we can use all the help we can get, whenever trying to start-up a bike that's been sitting for any extended time.
So I-myself wouldn't outwardly ignore Ducati's recommendation of having the alt.rotor properly timed.


Dukaddy-DUKEs,
-Bob

[Bevel bob]

I stand corrected!, In the uk the 160 was called the Monza Junior, I was thinking of the Monza settup , I would still junk any ET ignition components and convert to the 12v DC system used on the Monza/daytona/Mach 1, but perhaps that just because ET systems got such a bad press in the UK with competition disasters in the ISDT . In the Uk in the late 1960's you could not give away an ET bike which were not considered worthy daily transport .My mark 3 ,12v Dc Battery system now starts reliably Ist or2nd kick, and does not kick back like it used to. If i needed to start with a flat battery i would fit a cap in circuit.Perhaps the 125 is more tolerant with the greater static advance ET system but it can't be good for that ridiculously expensive B/End .Next time i remove my flywheel i will time it as Dct Bob suggests ,it can't hurt can it.

[3564cam]

Hello chaps,
This is what I think I will do.
1/ fit my Electrix 6v 12 coil alternator with modern reg/rec with charging light.
2/ I wont bother to time the stator as firstly there aren't any timing marks on the Electrix stators plus having spoken to them it isnt necessary due to the number of coils.
3/ Set the ignition timing as per the factory setting according to the chart previously posted.This was copied and pasted from the tech section in this site and is a Ducati factory document.It seems all the early 4 speed narrow case bikes had this extreme static timing.If it "pinks" then I can back the timing off.
It may seem overkill fitting this modern alternator but i do want to use this bike,with a headlamp on ,during the day and just dont want it breaking down.Both my 350 Desmo and Mach 1 let me down due to faulty alternators.
4/I am going to build a new wiring harness the same as the Mach 1 all 6 volt.
I have attached pictures of all the main component parts,I know Bob wanted to see the CEV rotor
Regards
Steve

[Bevel bob]

I'm a bit confused!!, are you still intending to use the ET system? if not then you need to junk the AC coil and AC points cam, if you are keeping the ET system then it will need an AC feed direct from the new alternator to the coil i think, perhaps DCT Bob will advise.

[3564cam]

Hi Bob,
I dont think my bike was ET(is this energy transfer?)The coil was wired to the battery live,it has the old Westinghouse reg/rec but still has a diode but not sure why.How can I identify an AC coil form a DC?How can I tell the difference between a ET AAU and a battery ignition AAU.I just want to be sure thts all before I fry something.All I know is that my Mach 1 AAU is different to the 125 but this may be because it need so much more static advance.All I want to do is to replicate the electrical system from my Mach 1 whcih is totally reliable.
regards
Steve

[DewCatTea-Bob]

I'm a bit confused!!, are you still intending to use the ET system? if not then you need to junk the AC coil and AC points cam, if you are keeping the ET system then it will need an AC feed direct from the new alternator to the coil i think, perhaps DCT Bob will advise.

____ Bob, I was meaning to have you clarify your thoughts/wording in your previous post, but you've now already confirmed what it seemed you were thinking before...
It now seems certain that you have the systems confused between the old 125s & the much newer 160s. _ As the 160s employ Ducati's energy-transfer system, while (I believe) all the very oldest OHC-models employed a system designed by CEV, which used a battery-powered ign.system. _ And that's what's been shown to have been original/stock on the 1958 125-Sport in question.
__ Hope this clears-up things (further).


DUCATIly,
-Bob

[Bevel bob]

For a battery system i would expect the points cam to be the same as the Mach1 type,if the 125 has a different one its posible that someone has fitted one from an ET bike,. With bikes this old just about every possible mistake can have been made and with my bike they were!!. Perhaps DCT Bob can describe the difference in the coil types so you can determine what you have ., I would be tempted to compare the advance ranges of the two AAU's, they look to have different ranges, dwell ,and springs.I'm also a bit surprised you did not go for 12v.Did the ign work well before? , On my bike i was told everything was refurbed ,but sadly everything was wrong and nothing could be taken for granted.Once the bike is running its possible to determine the max advance by observing the temperature gradient markings on the spark plug outer electrode, my 250 seems to need 38deg ,certainly not 41.Piston shape is a factor and mine is modified.

[wcorey]

The AAU on the right looks to be a 'standard' battery type aa359. The one on the left however is one I've never seen and has a number of differences from the two typical ones (for battery use as opposed to ET) I'm used to. The amount of dwell looks to be somewhere in between what the aa359 provides and that of the other 'standard' ET type aa367b but in my estimation looks closer to the aa359 (battery type). While the timing of it looks (cam position in relation the weights, etc.) to be very different from the aa359 the only way to determine that is from the relative position of the locating slot on the backside.
Would also be of interest to know how much advance it has...


Bill