Engine cuts in and out.

[72degrees]

210 ohms should, as Mark says, be OK.

In my experience, the earth lead to the crankcase is important. On my 250s (with 350 engines) I run it from the same earthing point on the frame that both the transducers use, but that's not really practical on a 350 with transducers up under the tank.

If you have a multimeter, another tactic is to measure the AC voltage output from the ignition winding while running (by hooking in to the green wire on a Morini). I've diagnosed ignition winding 'shorting' breakdown with heat on a couple of bikes that way (not Morinis to be fair). Running at steady rpm I could see the voltage start to drop rapidly when hot, then fail completely. Left to cool off, the voltage would return.

Having said that, I would have expected a failing ignition winding to possibly also make it more difficult to start again when hot, as well as misfiring or cutting out under load.

As Mark said, it would help enormously with diagnosis if you could isolate the misfiring as being from both cylinders or just one. It should be capable of starting and running smoothly on either cylinder. Mark's experience is borne out by mine. I once had to do about 20 Kms, two up with full Givi panniers, on a K2 running on one cylinder to get to somewhere to stay the night and sort it out (it was the pickup).

[Sicxtyone]

A few hours this afternoon and have tested the AC current from the ignition winding, at tick over around 90 volts going up to a shade under 100 at about 3/4000 rpm. Does this now point towards the transducers? The Pick up from my 500 I know to be good. The rear plug was certainly wet so I may swap over the 500 transducers as well and see what happens!
Be back at on Sunday
Graham

[mbmm350s]

HI Graham.
Did you make the measurements with a hot engine or just cold. We need to make sure the voltage holds up when it gets hot. The voltages you quote seem ok.
However since you have one pot that may be misfiring for sure try the 500 transducers swap. However as it's the rear thats suspect I would prefer to swap the transducers front to back and see if the fault moves to the front. If it doesn't then it's the generator or rotor as you have eliminated the pickup.

[MickeyMoto]

Are you 100% sure your carburettor are clean inside? Also, I have had problems with carb balance in the past which meant the engine bogged down in the mid range. May also want to check the air filters. How are the rocker clearances? How are the intake stubs? Not to say that when cold the rubber is nicely 'hard' but when warm cracks open up.

One other thing is to take care with quoting resistance figures as I am sure most meters will be lying like a lawyer paid by a multibillionaire Hungarian banker.

One magneto coil I measured at 250 ohms and had a weak spark, another at 300 ohms is ok. The bike does not run on the first but does on the second. Later rotors have an additional earth wire which attaches to the transducers. Have you checked resistance from the green wires at the transducers? Do you have a kill switch which may be is not properly 'open' in the run position and has a high resistance earth? The engine must be earthed as the spark will only happen if it can get back to the frame, as already mentioned. The transducers earth to the frame. May be worth checking the two points at the front of the frame where all the earths meet. I always use a multimeter to check every earth and that simple things like the engine cases and the frame earths to the battery negative are a short circuit. The plug leads also need to be 100% and I always change mine for copper ones. If you buy spark plugs on ebay be aware there are a lot of fake NGKs around. I buy mine from my local dealer.

Maybe you should go back to first principles and check EVERYTHING. Frustrating I know, but I am sure we have all been there in the past and had a Eueka moment.

Mike.

[Sicxtyone]

Hi mike,
Yes totally with you. I have a good bit of time tomorrow so am planning to be in the garage.
Have new air filters in there, rubbers to carbs are good, new copper plug leads, new ngk caps and new BP7ES plugs from a good local supplier.
Valve clearances checked and adjusted. The headstock earths are all bright and shiny with clean steel to bolt to, I have also put on an engine earth that I think 1976 bikes didn't have, back to the regulator mounting bolt earth.
What I am going to look at is the main ignition switch, connections especially the green wire. Also as you mentioned going to look at the carbs, then balance. If she runs long enough also strobe check.
Hopefully that eureka moment will come tomorrow and I am really thankful for your and everyone's helpful input.
Thank you all
Graham

[Sicxtyone]

I am very hopeful that my eureka moment has arrived, today replacement transducers arrived from www.pedparts.co.uk
They are the piaggio et3 and various other scooter, small bike units. Ducati electronica with the number 32398 1 1 2 £28.95 each. Just fitted them and a first kick starter the, engine feels smooth and strong. Tomorrow I can strobe and balance the carbs.
So looks like it was a transducer related problem. Fingers crossed, now I need to enlist an electrical wizard to make up the Rev counter modification. Anyone made up this small wiring loom mod?
Graham

[mbmm350s]

Hi Graham,

Nice one.
Do strobe the timing as the advance is different on the blue scooter CDI units.
I made a tacho driver circuit. Its pretty simple do you fancy having a go?
Will you be going to the Corsaro section on Saturday?



To any followers of this thread the blue scooter CDI units for PX125, PX150, PX200, ET3 are available from good scooter providers i used
https://www.wasp-performance.co.uk/duca ... -unit.html
oh no the secrets out - the Morini ignition is just a scooter ignition system with a special pick up.
Just check that they are ducati energie parts (made in India i believe)
and are marked with the number Graham showed.
Post 7/2011 Scooters may be restricted to 7000rpm due to Euro3 emissions so make sure its for a pre 2011 scooter.
But who regularly red lines a 40-45 year old strada anyway.

These are compatible with the red pick ups. There is no tacho output. The white is also an earth . You likely will need to extend the yellow earth.
I like to link the two white terminals to improve earth robustness.
Mark

[Sicxtyone]

Hi Mark,
Yes will be along on Saturday, I don't know if my soldering skill is up to the job! If you have a wiring diagram for the driver you made that would be a help. I do know someone locally ie next door who may be able to assemble it.
I've taken a picture from sorens video but it's all double Dutch/Danish to me
The yellow earth leads conveniently reach the air box mounting bolts, so just a wire from bianco to bianco?
If I can ride the 350 I will, best be off to the garage.
Thanks
Graham

[Sicxtyone]

So ok duh, I now have no tachometer so strobing isn't easy, also my strobe is playing up. Do I risk a 70 mile round trip to Petersfield tomorrow? I've put the original red pickup back in and statically timed and she starts and runs fine. A short potter around town revealed a higher than correct tick over but no amount of carbtuning would bring it down. I have stripped the carbs as well and discovered some cack in the front carb pilot jet housing, also the slide in the front has a lot of wear. Would this cause it to pull too much air and cause a high tick over as I can wind the stop right out and it don't make any difference!
Graham.

[EVguru]

Too much static advance will raise the idle speed. The static timing mark is just for initial setup to get the engine running.

No need for any indication of rpm, just set the timing at full advance. You'll see when it stops advancing with rpm.

[mbmm350s]

HI Graham.

Sorry if this is kind of obvious but you still have slack in the throttle cable.
My experience of scooter cdi is that they will idle fine once the ignition full advance is corrected if you put the pickup exactly where the old one was you will be like 10 degrees too advanced.
If you come to Petersfield I can give you the circuit for the adapter.
Cheers
Mark

[Sicxtyone]

Hi Mark
My neighbor is going to make up the circuit for the adaptor so am having two made one for my 500, just in case!
Graham.NnIcF3Kn

[norbert]

To make the confusion complete:
More than one pickuo, especially the red ones started his decline with problems when becoming hot. To me it happend two times. On my only trip I ever made with a tremezzo to England and Ireland in the beginning of the eightys it took me about 4 or 5 days till I found out that it only did run well when the motor became hot, when I took off the cover of the pickup. So I returned from Wales to Hamburg without that cover even raining Too days later the pickup broke down completely.

norbert

[Sicxtyone]

As an end to this post (fingers crossed) the bike now has the Rev counter driver fitted and is working nicely, accurate? Who knows. The engine starts very easily and idles reliably, I have replaced the carb slides, ouch! and I think this has really helped at lower speeds.
I need to recheck the strobe timing and re tweek the carbs but am very happy how she goes, for an old 'un.
Thanks to all for help and advice.
Graham.

[George 350]

The green wire supplies the voltage/power from the generator to the transducers. The ignition switch stops the engine by shorting the green to earth. It can be worthwhile the eliminate the ignition switch as the cause of your issues by removing the green wire from the back of the switch, or even better to run a wire from the generator green directly to the transducers to confirm that the wiring is ok.
George.