'73 Ducati 350 Ignition system

Ducati single cylinder motorcycle questions and discussions, all models. Ducati single cylinder motorcycle-related content only! Email subscription available.
Moderator: Morpheus

Moderator: ajleone

samsmc1
Posts: 2
Joined: Mon Jul 16, 2018 11:05 pm

'73 Ducati 350 Ignition system

Postby samsmc1 » Wed Aug 22, 2018 1:32 am

I decided to build a little Ducati single for a play bike. I have several complete bikes in need of restoration, but I want a small play bike and I'm not concerned about authenticity on this one, so I pulled an engine off the shelf and took it apart. I have what was a a very rough looking widecase chassis to put the engine in, so I'm 90&% there. The surprise came when I saw that the engine has a motoplat ignition - I looked up the serial number and discovered that it is a Spanish model (I have a complete one so I knew about them). I have a motoplat stator in very poor shape - the wiring is frayed right at the stator and I'm not sure I can repair it. I've also heard that they were of very poor quality (worse than CEV and Aprillia electrics)
My question is - can I pull the stator, flywheel and points from one of my older engines and bolt it on? This engine was in very nice shape with no wear in the cylinder and the guides were just within spec. Everything else looks very nice. I was a Ducati dealer years ago, so I have most of what I need to build this bike. All of my past experience was with the bevel drive twins, not the singles.
Thanks
Sam

Jordan
Posts: 795
Joined: Fri Dec 24, 2010 11:29 am

Re: '73 Ducati 350 Ignition system

Postby Jordan » Wed Aug 22, 2018 5:14 am

All the widecase singles have the same mounting arrangement for the stator and rotor.
So you can install any system that was made for widecase engines.
Narrowcase engines are dimensionally different, so you can't readily use their electrics.
In the case of Ducati's own CDI, these have 2 cables that need to come out through the crankcase, and these engines have a larger hole to permit that.
The Motoplat CDI has only one cable, doesn't need a bigger hole, and uses the same crankcase as for the points ignition systems.
It might be possible to use a Ducati CDI with a small hole engine, especially if a single cable with all the conductors in it were used, rather than 2 cables.
You'd need to keep the same size of copper cross sections or bigger.
Being not potted, soldering new cables to a Ducati CDI stator is not difficult.
There are 2 systems using points - one for use with a battery, one that doesn't need a battery.
Coils and advance-retard units differ between them, as well as some wiring details.

samsmc1
Posts: 2
Joined: Mon Jul 16, 2018 11:05 pm

Re: '73 Ducati 350 Ignition system

Postby samsmc1 » Wed Aug 22, 2018 2:10 pm

Jordan, thanks for the reply. You answered my main question in that all the wide case models have the same stator mounting holes. This leads me to the next question - which Ducati wide case singles used a cdi ignition? Are any of them available? Which ignition system would you use building a bike from scratch? I have several more wide case singles I can rob parts from if I need to.
I do have a '70 model 450 engine that is complete minus the head that I sold 30+ years ago when they weren't worth much. I would have used that engine except for not having a 450 head. Any idea where I might find a 450 head (springer or desmo) for this pup without having to rob a bank?
Thanks
Sam

Jordan
Posts: 795
Joined: Fri Dec 24, 2010 11:29 am

Re: '73 Ducati 350 Ignition system

Postby Jordan » Wed Aug 22, 2018 10:27 pm

Original new CDI not easy to find now, but aftermarket systems exist.
A stator from a points type bike can be adapted to provide charging current for a CDI, using a coil from another maker to replace one of the existing coils. That leaves the pickup assembly to be found, and the CDI/HT coil.
Attachments
DSCN0058.jpg

graeme
Posts: 593
Joined: Sun Mar 25, 2012 12:00 am
Location: Australia

Re: '73 Ducati 350 Ignition system

Postby graeme » Thu Aug 23, 2018 7:22 am

Scrambler club in Italy?

ducwiz
Posts: 270
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: '73 Ducati 350 Ignition system

Postby ducwiz » Thu Aug 23, 2018 9:49 am

This company http://www.uk-motoplat.com/home.html in the UK might be able to repair the Motoplat stuff. I have no personal experience with them. On the other hand, these spanish parts are known for premature failure, a weak spark resulting in difficult starting, etc. The Ducati CDI version is much better, but hard to find these days. Warning: you should not/cannot mix Motoplat and Ducati parts, for different reasons.
So, a conversion to an older 6-coil stator and points ignition is recommended as the cheapest solution. Of course you need a 6V ignition coil, the points/plate and an appropriate AAU. If budget is not a problem, you should consider an electronic ignition (i.e. SACHSE MHP) or a 12V alternator/regulator/ignition conversion kit from Electrex/UK.
Helotronik, a german small business company, offers an electronic ignition kit for a reasonable price: https://translate.google.com/translate?hl=de&sl=de&tl=en&u=http%3A%2F%2Fwww.helotronik.de%2Fkontaktlose.htm

Image

cheers Hans

Ventodue
Posts: 474
Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: '73 Ducati 350 Ignition system

Postby Ventodue » Thu Aug 23, 2018 4:24 pm

samsmc1 wrote:. This leads me to the next question - which Ducati wide case singles used a cdi ignition?

Some Scramblers (1972 on), some Desmos, possibly some Mark 3s(?). Sometimes Ducati Elettrotecnica/Elettronica, sometimes Motoplat, often according to year, also cc.

samsmc1 wrote:Are any of them available?

Yes. Second-hand, for sure; but obviously you take a risk that the electronics work - and will stay working. After all, we're talking 40 year old technology here.

New, from Ducati Vintage Store - transducers and pick-ups, for example. Go:
http://www.ducativintagestore.com/light ... &sort=&fp=

But see my response to your next question ...

samsmc1 wrote:Which ignition system would you use building a bike from scratch?

Not the original - even if I'm personally still running a bike with original equipment. If I were starting from scratch, I'd buy new and modern. Others have made various suggestions as to providers, Ducati Vintage Store also do modern kits, both 6 and 12 volt.
http://www.ducativintagestore.com/light ... &sort=&fp=

HTH

Craig


Return to “Ducati Singles Main Discussions (& How to Join)”

Who is online

Users browsing this forum: No registered users and 23 guests