Transducer

Lambertini era singles (125 and 250 - half v-twins)
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125H
Posts: 97
Joined: 30 May 2018 18:36
Location: Loughborough UK

Transducer

Post by 125H »

Hello all,

does anyone out there have an original black transducer in working order number 323921 that I can borrow?
hendre
Posts: 600
Joined: 11 Aug 2007 06:51
Location: The Netherlands

Re: Transducer

Post by hendre »

the 323921 is also for the 1st series 3 1/2's, you can use a replacement. There info on the forum about what is available to replace the older boxes.
hendre
Posts: 600
Joined: 11 Aug 2007 06:51
Location: The Netherlands

Re: Transducer

Post by hendre »

https://www.ital-web.de/forum/viewtopic.php?f=7&t=7470
on the same forum there are good experiences with the Ducati Energia 32398112 transducer used for Vespa PX 125 150 200 / Cosa 125 - 200 / PK 50 125 S XL XL2
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Transducer

Post by mbmm350s »

Hello
hendre wrote: 01 Sep 2022 08:05 https://www.ital-web.de/forum/viewtopic.php?f=7&t=7470
on the same forum there are good experiences with the Ducati Energia 32398112 transducer used for Vespa PX 125 150 200 / Cosa 125 - 200 / PK 50 125 S XL XL2
New and exact substitutes for the original black transducer with tacho output can be obtained from Alex Luzzi as Hendre says.
Yes we are testing on a 350 right now. The same transducer as used on the 125H.

I have already posted that we do not think that the 125H being crank timed will have enough stator rotation adjustment
to be able to use the Blue Scooter transducer Ducati Energia 32398112 on a 125H.

The scooter application (PX etc) has 18-23 degrees (crank) of advance, the 125H has 36 degrees. This means that the stator has to be rotated by as much as 18 degrees, this does not seem possible.

I think also you need to confirm that the pickup coil (on the stator) is the correct one and equivalent to the 125H. The direction of the pickup coil winding and the shape and polarity of the trigger magnets affect the generation and timing of the pulse. Without any intervening diode the trigger waveform will go negative then positive or vice-versa, I do not know which it should be.
Its normal to go negative first then positive, because in this way the rising portion of the waveform is better controlled. To make sure that the trigger pulse is the correct waveform and timing requires a two channel oscilloscope. The positive excursion of the waveform should be around 36 degrees before TDC ( ANT=ANTICIPO). The actual point on the waveform of the trigger voltage is typically around 1.2V when there is a diode somewhere, it is usually easy to spot because there is an interference spike. You will need to make a small trigger on the rotor for TDC to feed the second channel of the oscilloscope as reference, a specialist automotive electrical expert can do this. To avoid engine damage I would take to someone who can do this on an starter roller or can rotate the engine, at lower speed the timing point will be closer to 20 degrees before TDC.

Interference to the trigger pulse is not uncommon if the earths are poor. Or the frame is heavily painted as the transducers rely on earth via the headstock.


Best regards
Mark
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themoudie
Posts: 132
Joined: 13 Jan 2007 21:24
Location: Perthshire

Re: Transducer

Post by themoudie »

Good afternoon Gentlemen,

This 125H single problem is now spread across 3 threads! :roll: Confusing for any future reference by a similarly suffering soul! :? :? :?

So, I shall post this information across all 3 threads and then stick with the "125 with no spark" thread only. But, read the others for any further positive or negative developments.

I despatched my entire generator/ignition system, including both my original Ducati Elecctronica # 323921 and Ducati Energia #32398112 transducers (CDI/HT unit) to Rex's Speedshop, but due to staff problems and after 10 weeks, I requested that he return the whole lot to me. This he did, in short order and with no problems.

I then despatched the entire system to another experienced auto electrician, with the necessary oscilliscope facilities and experience of these scooter derived systems. After testing the individual components, he dynamically tested the system, with both the black Ducati Elecctronica #323921 and blue Ducati Energia #32398112 transducers in place. The component that appeared to be malfunctioning was my original trigger coil that was not showing a negative wave on the oscilliscope. The replacement (Lambretta type 12) that I had fitted did show the positive and negative waves but did not align with the cutaways in the flywheel that cause it to create the trigger signal. So another Italian trigger coil of better quality and fit was fitted to my stator and the working air gap checked. He too was of the opinion that there is nothing wrong with the quality of the Ducati components and system robustness, as a whole.

Today, I re-checked my valve timing, then fitted the stator etc. Connected all the stator wires to the black # 323921 CDI/HT unit and the RECT/REG and fired the engine up. A definite improvement to the ability to fire up and a good strong increase in the revs from a 1,300rpm tickover to half throttle (3,500-4,000rpm), when the stuttering re-appeared and any further opening of the throttle caused the engine to cut out abruptly. Using the timing light, a marginal movement of ~5°to the left of the 'ANT' mark on the rotor (advancing) preceeded the engine cutting out.

I then repeated the procedure, with the REG/RECT and ignition switch wires disconnected, with the same results.

The black # 323921 unit was then replaced, with the #32398112 unit, again starting with all of the connections made then disconnected and the exact same symptoms were recorded! :evil: This would tend to discount the notion that the blue #32398112 unit is not a workable alternative to the black # 323921 unit. Or, the cause of this particular set of symptoms.
Interference to the trigger pulse is not uncommon if the earths are poor. Or the frame is heavily painted as the transducers rely on earth via the headstock.
To avoid this, I have renewed the earth lead from the REG/RECT mounting bracket to the upper rear crankcxase bolt of the engine and also used an additional white wire between both CDI/HT units and the REG/RECT mounting bracket bolts, to ensure a good earth between all of the components.

I am not convinced that fitting a
New and exact substitutes for the original black transducer with tacho output can be obtained from Alex Luzzi
will cure the problem.

Thank you all for your time and thoughts.

Good health, Bill
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