ignition timing

[Eldert]

the AA unit on the left looks like a CEV one to me

Eldert

[Bevel bob]

I know just what your thinking Bill !!.

[3564cam]

Hi,
The unit on the right does say "AA359".The one on the left from the 125 says "6602"If you line up the slots the pivot pins for the bob weights line up too so you can compare the cam profile and position.The springs on the 359 are stronger plus this unit has more advance.The factory specs for each unit are 5-8 degrees static for the 3359 with 33-36 degrees total,while the 125 is 18-20 static with 46-48 total.Maybe this explains why the cam is different with a more advanced postiton relative to the slot.

[wcorey]

The timing on those is quite different, I wonder if the timing mark on the drive gear is different also.
Makes sense that it would be a CEV, as the alternator is too.

Bill

[DewCatTea-Bob]

By: 3564cam...
" This is what I think I will do.
1/ fit my Electrix 6v 12 coil alternator with modern reg/rec with charging light. "

____ Why do you seem to consider your Electrix-alternator as "6v" ?

____ BTW Steve, thanks for submitting your posted pix of your stock 125-parts !

---

" I dont think my bike was ET(is this energy transfer?) "

____ As has become concluded, your OHC-125's ign.system is not the 'energy-transfer' type, (unlike the '125-Bronco'), since your 125's pictured AAU is not the correct type (for the E.T. type of ignition) !


" it has the old Westinghouse reg/rec but still has a diode but not sure why. "

____ It's fairly doubtful that such a "reg/rec" is an original/stock item, cuz back-then the electrical-systems were expected to be more or less 'balanced' (between power-production & power-consumption), with the battery handling any occurring power-imbalances.
__ Do you have a picture of that "Westinghouse" item ?


" How can I identify an AC coil form a DC? "

____ With the 'Ducati' ign.coils, the 'red-label' coil is for battery-type, and the 'green-label' coil is meant for the E.T. type of ignition. _ If the original label is missing, the coil-body includes identification-marks stamped on the base-end, (however I don't recall those particular figures now).
__ I don't recall the related details for the ign.coils used with the CEV-systems, but I'm quite sure that they at least have 'CEV' on them (if not also 6v.DC as well). _ So if your 125's ign.coil has "CEV" on it, it's then certain to be for use with the battery-powered type of ignition-system. _ (Otherwise I'd instead expect it to state 'CEV' & 'AC' upon it.)
Do you have a picture of the ign.coil that's from your 125 ? _ (So I can see if I recognize it.)


" How can I tell the difference between a ET AAU and a battery ignition AAU. "

____ Check-out the following link (to a thread by 'wcorey' / Bill )..... viewtopic.php?f=3&t=428&hilit=advancer+AAU#p2972
If ya can't see the right-side of his (otherwise very-fine!) posted-pix, then download them into your PC and open, for full-viewing on your mon.screen.


" 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. "

____ No-doubt the main reason for the obvious differences is due to your early-produced AAU not having been made by Ducati, and not merely because the intended static-advance settings are not the same.


DUKE-Cheers,
-Bob

[Bevel bob]

It would appear that both units have the same 28 degree range (fitted) ,its likely that the smaller 125 sport motor is more tolerant in use with the advanced static setting than a 250 and maybe has a less efficient combustion shape with a high piston and needs the extra advance , I would start off with less than spec as i am told todays fuel burns faster, --it certainly burns richer .

[DewCatTea-Bob]

" It would appear that both units have the same 28 degree range "

____ Well if the mentioned chart is indeed a factory-produced document, then simple-math obviously confirms that the 125-AAU's adv.range is indeed 28-degrees (between static & full-advance) !


" its likely that the smaller 125 sport motor is more tolerant in use with the advanced static setting than a 250 "

____ And of-course the likely kick-back is twice as easy to overcome.


" and maybe has a less efficient combustion shape with a high piston and needs the extra advance "

____ The most likely reason for the greater advance setting is that the combustion-chambers of the pre-250 OHC-models did not include a 'squish-band'.


" I would start off with less than spec "

____ I certainly would not start-out with the max.advance set further-out (from TDC) than the minimum recommendation of 46-degrees BTDC.


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

By: wcorey...
" The timing on those is quite different, I wonder if the timing mark on the drive gear is different also. "

____ I'd assume then that the OHC-125 AAU.drive-gear's timing-dot is located at the standard-position, unless the orientation of the 125's breaker-cam is pre-set considerably more than 6-degrees (12 crankshaft degrees) further advanced (than the AA359-cam's preset-orientation).


" Makes sense that it would be a CEV, "

____ If the 125's AAU was actually made by 'CEV', then I'm pretty-sure the unit would then include CEV's "CEV"-icon/name somewhere upon it.
Otherwise, either CEV or Ducati probably had it manufactured by a subcontractor.


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

By: 3564cam...
" plus this unit has more advance. "

____ Not clear on exactly what this wording was actually meant to state.


" The factory specs for each unit are 5-8 degrees static for the 3359
while the 125 is 18-20 static
Maybe this explains why the cam is different with a more advanced postiton relative to the slot. "

____ Indeed so, cuz since the 125 requires 12-degrees more advance, then the breaker-cam lobe-ramp's preset-location would thus also need to be equally more-advanced (than that of the 'AA359'), in order to still fall within the provided range allowed within the adj.slots (of the mounting-plate).


Duke-Cheers,
-Bob

[3564cam]

Dear all,
The information regarding the ignition timing was taken from this site and is indeed a factory document.It also gives a wiring diagram showing a "westinghouse" regulator.My 125 was all running fine,charging fine but when I checked the wiring it was all 50 yrs old and patched in places.So hence I have built a completely new harness,fitting the new Electrix alternator,plus reg/rec.My understanding now is that these early singles have an alternator,with battery igniton DC.The current regulation to the battery is governed by switching on one or two coils via the headlight switch.This is similar to early pre unit Triumphs.
So my bike has a DC coil,correct AAU,the Electrix 12 coil alternator is 6 volt as I asked them to supply it to me as such,with the option of a charging light.I will post some pictures of the original regulator tomorrow.It is the finned type and bolts to the frame behind the battery.See the full document taken from this site.It says this booklet is for "magneto" bikes but I think this is misleading as we have recently discovered from the very informative posts on this thread.
http://www.motoscrubs.com/Ducati_Electr ... agneto.htm.
Regards
Steve