rich running

[Jon Pegler]

What plug gap are you running?
The Ducati Electronica electronic ignition does not produce a very fat spark like modern electronic ignition systems.
I have this ignition on a couple of my Ducati singles and run a plug gap of about 0.020 thou (0.5mm)
Running a wider gap doesn't seem to suit this system, and most plugs come with a much wider gap nowadays, usually about 0.040 thou or 1mm to suit modern electronic ignition systems.

Jon

[Duccout]

Jon's suggestion is very good, I've had old bikes in the past with ignition problems that have run perfectly when I closed up the spark plug gap. My 900 Ducati stopped firing on one cylinder and I found that if I reduced the spark plug gap it cured it. Didn't save me from buying a new transducer though.

It would be interesting to try riding it with the air cleaner rubber bellows off. I have heard of old Ducatis having air flow problems due to the rubber bellows being sucked together and starving the engine of air.

[Jordan]

Can anyone tell me how the Ducati Eletronica ignition system does its advance, I assume it is all totally electronic with no owner adjustment.

Ignition timing is adjustable, in a "set & forget" fashion.
The signal inductive pickup is on the right side of engine. The backing plate that holds the coil is slotted and can be moved to alter the ignition timing point. That is done at a pre-determined engine speed, as per factory specification.

Ignition advance is analog type, taking advantage of the fact that voltage increases with speed of magnet moving past the coil. See Faraday's Law.
For each revolution, the pickup coil makes a roughly sine type wave form, going up and down each time.
Faster the revs, steeper the wave form, which means it reaches the trigger point sooner. And vice versa.
That gives the advance/retard effect, simply and reliably.

[Scottish888]

Took the plug out, it was a little damp with fuel even though it was running fine on low revs on way home.
Cleaned it and set the gap to 0.5 mm it was 0.6 (NGK B6HS)
Also have a Champion L82C, anyone tried these? I think it is a correct alternative.

Regards

[Dan C]

I had very similar symptoms on my 450, wouldn't run above 1/4 throttle about 4500rpm (Post "450 desmo not running cleanly").

Change of ignition from standard Ducati Electronicca to Sachse made no difference.

Buggered around for ages trying all sorts of settings on the VHB 29. Eventually got it a bit better but was running very lean.
Finally pulled the VHB off and replaced it with a PHF30 off the 350 and it is much better although still runs leaner than I'd prefer.

Put a VM30 Mikuni on the 350, which so far seems excellent despite me having no idea where to start with jetting. (Post "Mikuni Carb Settings)

So for my two pennies worth, I'd suggest changing the carb before worrying about the ignition.

[Dan C]

Jordan wrote

I don't know what I'm doing wrong, but I get fantastic reliable performance from my VHB.

Jordan, can you advise how much slide wear you have in your VHB?
I get 0.6mm in one and nearly 1.00mm in another. That's putting the feeler gauge between the front of the slide and the carb body. This is after the slides were recoated.....

Cheers Dan

[Jordan]

Wear on my single's carb slide is slight. There is no ridge on the flat face.
A characteristic of VHB carbs is that there is spring force acting to push the slide against one face of the throttle body.
So, any fore & aft slide play is not proof of undue wear. I think they were made fairly loose.
I do not do great mileages.
For much of my single's life I ran with no air filter, but I now have 1.2km of dirt track to my place so a foam filter sock is used, sadly.

[Scottish888]

Thanks folks,
Will first try with a new home made rubber gasket, no air filter, new plug
if still nothing after 4500 rpm, I will swap out the carb, will try to use an OKO Keihin copy flat slide carb, I have a brand new 30mm ID unit but will need to buy/make a manifold adaptor. Mikunis are fantastic but I like the Taiwanese OKO's...when I can buy them in the UK.
I really don't like the strong spring used in the Dellorto, makes a light bike feel heavy.
What I did notice on the VHB was there is no paper gasket in the top lid, on youtube some guy was showing a carb rebuild and this gasket was fitted.
I know it could be the source of an air leak but I don't think it will make that much difference...or could it? I think most carbs leak air from the throttle cable anyway. Not an easy gasket to make.
I am making the mistakes so you don't have to

Regards

[Dan C]

Thanks Jordan
I share your pain, we have 5kms of gravel road....and the Council only grade it about every 18 months.......

[Dan C]

For what its worth I fitted all new gaskets and "O" rings to the VHB (including the top gasket you mention) and it made no difference.
But a big improvement when I fitted a new carb.