125H problems

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

Re: 125H problems

Post by 125H »

Hi Bill,

thanks again for your help and support, I may well be able to find a rolling road set up near me but on previous investigation the comment was where do we plug in the laptop how will we flash the ignition? Its a problem with a 40 + year old machine and then as you say its getting it there, certainly would not attempt to take it on the road so will have the cost of further transport and to possibly to no avail. I did have my stator rewound and have to assume it was done correctly - although have noted the pickup is marked GB so may not be Italian, but this is a simplistic motor scooter system so should work.

It reminds me a little of a friends Royal Enfield some time ago, they are all gear driven in regard of valve timing and ignition and at some point in cleaning out the timing chest he had moved things about and the the bike although it would start and tick - over OK would run for perhaps ten miles then stutter not pull and bang and get hot and stop, he brought it around to me and he had the ignition well retarded lining up all the marks cured his problem, so I am convinced that the problem with the 125H it that it does not advance for some reason either electrical or mechanical possible due to the crank position, in regard to the timing belt and pulleys but to be be mechanical its doubtful. I did note that on the outside of the rotor there are two what appear to be scribe marks and wonder if they are of any relevance but as the rotor is keyed on it cannot be in the wrong place either.
My knowledge of CDI ignition is poor being from the magneto/dynamo era and I have no equipment at home for testing things like this, back in the day it was a timing disc and a battery and bulb!

Thank for your comments.

Regards
Leonard.
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themoudie
Posts: 132
Joined: 13 Jan 2007 21:24
Location: Perthshire

Re: 125H problems

Post by themoudie »

Good evening Leonard,

I too was dynamo and magneto reared (1953 AJS 18S) and moved onto the Ducati, with at the time the new technology, 1974 CDI ignition and alternator, not disimilar to the set up found in the Moto Morini v-twins and the 250 single, with the timing controlled by a trigger in the place of the AAU and points in the timing chest, driven by gears off the crankshaft. The Ducati ignition went phut, I had no money and reverted the ignition to AAU and points that were familiar. Oh, for a Rizla green packet and papers to set the points! :lol: :lol: :lol:

Went for a run today to see the local Dynomometer owner and he appears to know his stuff. However, his electrical guru is a man who thinks in a "different way"! His words, not mine. He is a freelance, who comes in to sort out the race bikes and enjoys challenges. So, there is going to be a conversation this weekend between the dyno owner and the freelance sparky. Next week I will contact the dyno owner and see whether the challenge has been accepted and if it has, arrange for the transport of The Minx to 'muchty. Time will tell! I'll keep you posted.

Regards, Bill
125H
Posts: 97
Joined: 30 May 2018 18:36
Location: Loughborough UK

Re: 125H problems

Post by 125H »

Good morning Bill,
I wish I could convert this back to points and a coil, think life would be much simpler.
Please let me know how you get on with the electrical guru, will you also ask if he travels, some times they have a mobile workshop/van and if he cures your problem he may travel to me.
I'm at the point now having overspent on this restoration that I would be happy at almost any price to have a fix to the ignition, or call the local scrap man! I have even put on hold the fuel tank leak repair just in case its a further waste of money!

I am planning to go through it again piece by piece to try and identify a fault or issue and in regard of that do you know anyone who re - magnetises the rotor magnets?

Then I will try and find someone to check the stator over for faults, then I will go over all the wiring again. I still remain unconvinced there is not an issue with the transducers not working as they should. Internet searches identify many, many, different types going right back to the 1970's so finding the right one could be a problem - they don't come with any information!

Regards
Leonard.
User avatar
themoudie
Posts: 132
Joined: 13 Jan 2007 21:24
Location: Perthshire

Re: 125H problems

Post by themoudie »

Good afternoon Leonard,

Rather than going through the whole thing again, it might be better if you could sit on your hands, until after I have had mine run up on the dyno. The angst won't be doing your blood pressure any good. :wink:

Paul Compton re-magnetises rotors, if required, but as you probably know, this is not a permanent fix, as the magnetism slowly declines over time.

As for your comment
I still remain unconvinced there is not an issue with the transducers not working as they should. Internet searches identify many, many, different types going right back to the 1970's so finding the right one could be a problem - they don't come with any information!
I too think that having been independently tested and producing the same test results for me and independently, my two CDI/HT modules are sound. Having replaced my wiring from the low tension and trigger coils to the CDI/HT module and it too independently tested, I know that is OK, as well. As for "information" on the internals of CDI/HT modules from the '70's, you must be jesting! :evil: :evil: :evil: The only way to find that out is to dissolve the potting plastic and hope that it doesn't dissolve the encapsulated components at the same time. :evil: :evil: Reference the Moto Morini Owners of Nederland website
Repair:
At the bottom of each transducer you will find a dark-red potting substance. You have to carefully remove this. You can use "dimethylsulfoxid" (C2H5OS) and mix it 1:1 with "aceton" (nailvarnish remover) (C3H6O). This mix will solve the potting substance. It is a time-consuming process and you have to be careful you don't destroy the contains of the box and the housing. When a transducer is broken, it is mostly the coil or the thyristor that needs replacing.
Ducati Electronnica didn't want anybody to "repair" these items and having gone into receivership/nationalisation more than once since the 1970's, the old adage "A new broom sweeps clean!" appears to apply to their old design/component data. Why would you bother, when the next module incorporates the latest miniaturised circuitry and micro-processor? :wink:

At present The Minx is under wraps in the workshop and can sit there undisturbed until I have the dyno run sorted out.

Slainte, Bill
125H
Posts: 97
Joined: 30 May 2018 18:36
Location: Loughborough UK

Re: 125H problems

Post by 125H »

Hi Bill,

will probably take your advise and sit on it, by the way did you have your stator rewound or is it the original, although I suppose it could have been rewound over the years and before you had it.

I had mine done and I would like an independent check to see if its OK if it was rebuilt correctly the insulation should not break down as you mention.

I will speak to Paul in regard of checking and re - magnetising the rotor, hanging spanners on things hardly seems that technical to me and a 40+ year old magnet must have lost some power.

Regards
Leonard.
User avatar
themoudie
Posts: 132
Joined: 13 Jan 2007 21:24
Location: Perthshire

Re: 125H problems

Post by themoudie »

Evening Leonard,

No, I didn't have my "stator rewound" as there has never been a problem with the 6v charging side of the electrical system on The Minx; it being separate from the ignition system.

I did replace the low tension coil, as a unit, as this is relatively easy to do. But after independent testing was told that the original low tension coil was in excellent condition and of better quality than the one that I had replaced it with. So, the original low tension coil was re-installed on the stator. Before I touched it, the original stator hadn't been altered, as all the soldered joints were covered by the original Ducati Electronnica insulation paint.

As for hanging spanners from the individual rotor magnets, whilst not "technical", I am not sure how else you would do it, unless a specific weight of keeper was specified! :?

Regards, Bill
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Ming
Posts: 798
Joined: 01 Aug 2014 16:32
Location: France
Location: Central France

Re: 125H problems

Post by Ming »

Just a couple of points. If the rotor and stator have been in position from build, there should not be a ’leak’ of magnetism. As Paul C says, the cdi units do nothing other than produce a spark. The circuit internals are shown on a cct diagram on the Dutcb site and can be built with some moderate soldering skill.
Are you certain it’s ignition related?
125H
Posts: 97
Joined: 30 May 2018 18:36
Location: Loughborough UK

Re: 125H problems

Post by 125H »

Hello Bill/Ming,

thanks for the input, my rotor stator was in poor condition so I had it cleaned and rewound, most of the insulation on the wiring was peeling off and it was full of road dirt and grease - or probably off road dirt. They are partially open to the elements, not a good idea in our climate.
As to transducers I agree they only fire the ignition but am told by 'experts' that they also advance the ignition in line with the rpm of the engine, and that the one I have is just that - straight line ignition with no advance as it was designed for a motor scooter, two strokes of course require little or no advance.

I think that both Bill and I have eliminated mechanical or carburation faults between us and it was often said that most carburettor faults are ignition related. We tried three different carburettors on my 125H with the same result so unless I have completely screwed up the valve timing don't no where else to look other than ignition, a friend in Italy thinks it may be a problem with the pickup but Bill I think resolved that with his testing. For now I am going to sit on my hands or probably with a beer glass in one hand and await Bill's trip to the rolling road and electronics guru, hope that producers a result.

Just as an observation, it would appear almost as if something's reversed somewhere, as the PMS mark with a strobe aligns with the camshaft and the ANT mark is over to the right by about 30 degrees retarded instead of being where the PMS mark is and will not move from there (advance)- happy days!

Regards
Leonard.
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