rich running

[In Two]

I'm sticking with this thread to continue the saga of my misfire on the 250D and have a couple of relevant questions.
I've just fitted a Sachse ZDG 3.10 ignition, Dyna coil, new NGK resistor cap and HT lead all supplied quickly, efficiently and expensively by Sachse.
I wanted to change everything in the ignition chain in one go from a known source, my goal was to get the bike working and prepped for the MotoGiro D'Italia rather than diagnosis. Well, it worked! Started first kick, ran strongly through the rev range with just a slight 'stumble' on transition from about 1/8 to 1/4 throttle but no trace of the previous misfire. There was also the occasional backfire through the carb at the same sort of throttle opening which I guess indicates slightly advanced timing or the carburation problem... VHB... that has been there all along, now reduced in effect by a good strong spark. I didn't have either a strobe light or the pointer thingy or even a timing disc with me in Poland , they are in Italy with the twins, so I bought a cheap strobe, cant find a degree disc here (too old school?) and made up a pointer thingy out of an 8mm bolt, a perspex disc marked with a white line from centre to edge and a handful of nuts, washers and o rings. I couldn't index it with the notch in the crankshaft except by eye so here's my first basic question; Is the notch in the left end of the crank at the top , in line with the cylinder axis at TDC? It seems so to me and makes sense, but I don't have the original pointer thing with index tab to check.
Second question; wiring up the Sachse ignition and Dyna coil involves making a very simple sub loom with a switchable power supply to and from the ignition box and the coil. The original power feed to the Ducati Ellectronica ignition module is, I believe, fed from one of the windings in the alternator via a white and green cable, now both brown and crumbling and surplus to requirements, should I keep the conductors apart or short them? Does it make any difference?
Sorry about the dumb questions but the last time I worked on and rode a Ducati single was nearly 50 years ago, the intervening years have diminished neither the joy, nor the vibration...
Cheers
Zed
P.S. I'll get onto the LEDs etc when it's running perfectly, who needs lights.

[Duccout]

I'm not surprised that the bike runs much better with the new ignition; I remember how fitting a Lucas RITA to my 750 totally transformed it.

[In Two]

Yes, I fitted a RITA to my 900ss just after John Carpenter invented it and it worked brilliantly until one dark night on the way to the TT, the bolt holding on the rotor loosened (my fault entirely).The rotor spun round about 90 degrees then tightened again, lots of sitting in a puddle at the roadside making degree discs out of cardboard boxes and school protractors ensued.
Anyone have an answer to the old electronica ignition power feed question, leaver it open or shorted? I left it open and everything seems to work... so far.
cheers
Zed

[blethermaskite]

Zed, I have reverted to good old points and a coil on my 250 desmo ......starts first kick, revs clean as a whistle to "nipon seiki"......the original power feed wire for the cdi from the alternator on mine is just dead end isolated. I have lucas rita on my 350 mk 3 and the same dead end wire from the alternator (its been like that now for about 15 years with no issues). Re the stutter/misfire.... this is the sort of really irritating nonsense that I have experienced for years with those bloody awful VHB carbs, I just chuck em and fit a Mk1 aml concentric
Cheers,
George

[Scottish888]

Update:
Got the points ignition fitted and timed it best I could with a timing wheel, static points open at 6.5 deg btdc, no idea about the advance timing.
Impossible to check the advance with a dodgy timing wheel set up.
Got the bike fired up, would not rev beyong 6k, it would begin to run rough then cut out until the throttle was closed a bit.
Stripped the original Dellorto and fitted a new gasket and seal overhaul kit, the bike then run worse than ever!? so I dumped the carb and fitted a brand new OKO 30mm carb.
I just needed a carb that worked cleanly so I could check to see if the points ign setup performed better than the original ducati electronic ign.
Bike started easily, very clean running until around 6k..just nothing after that, a few pops and gasping was it till the throttle was closed a bit.
So, it does not look like the points ign system made any difference...also two new carbs have made no difference.
Tried both carbs with the airfilter hose connected and with it off, no difference.
Last year I fitted a brand new Mikuni VM30 when it had the original electronic ign fitted, that made it run better but it still would not rev beyond 6k.
Today andother brand new carb (OKO) tried with the same result. I have used these OKO's on a few diffeent machines and rate them very highly.
Will put the original electronic ign back on and try that with the OKO carb but I am not hopeful.
So, two complete and different ignition systems, three carbs (two new) and it still wont go beyond 6k.
Running out of patience with this bike, not easy to sell but..

[themoudie]

Morning Alex,

Deep breath!

Back to basics. If the ignition isn't timed right then the engine isn't going to run right, regardless of the carbie that you stick on it.

I will send via email a useful article for timing. Be aware that it was the AAU that was giving me the grief, even though it all appeared mechanicaly tickety boo and within spec.

Whilst Sachse appear to be sound systems and many people swear by them, I went the Electrex route, which isn't "tuneable", but has proved very satisfactory on the 450. The strobing being done on the righthand side of the engine, so that you don't have to be in two places at once!

Even with a carb (AMAL MKII 2932) poorly set up and with a naff exhaust, I obtained a steady tickover and a base from which to sort out the carb.

Perseverence.

Good health, Bill

[Scottish888]

Thanks Bill,

Been reading through your pdf, what a procedure!
I suspect it is ignition related rather than carb but with fitting two new carbs with the same result it certainly looks like ignition.
It could be that the original electronic ign was not advancing and I am also having advancing issues with the points mechanical setup.
I have been frustrated with the dodgy timing wheel setup I have, it is impossible to be more acurate than one or two degrees due to this being a bolted on setup, the margin for error is always there.
I will try just focusing on the fully advanced timing with the method you kindly forwarded, even then I will be out but could a couple of degrees out but could that cause no rpm after 5-6k?

Regards

[Bevel bob]

My 250 is not fussy about timing and will run ok from 32 to 38 degrees advanced. It has the nominal 10 to one ( about9!) piston , A cam with more overlap than a green white and a 40 mm inlet fed by a 29mm SSI. To avoid starting naughtiness I run with about 5 degrees static advance , so probably a bit tamer than it could be.

[Scottish888]

saga continues,

Found tdc, set the crank back then forward to 36 deg btdc, locked the advance unit into full advance and set the points to open at that 36 deg point.
Check all again then released the advance unit and tried to start the bike, it tried to fire but would not run.
I stripped out all the points ign system and replaced all with the original ign system.
Set the piston to tdc with the rotor lining up midway along the pick up section, one of the tips of the rotor lines up exactly with a mark on the stator at tdc.
I then set the crank to 36 deg but could find no marks that lined up with anything so I made one of my own.
At least I can easily identify tdc on the electronic system.
I'll need to check how to set the static but I know the bike starts easily in this position and it did but it showed up the jets in the new OKO carb are too small so running weak as the choke was needed to keep it going.
I wondered why the Dellorto run badly after fitting a rebuild kit so I stripped it to see what I had gotten wrong. Turns out it was my fault (as usual)
I found a little corrosion inside the main body in what looked like a blocked port, so cleaned it all out and it looked like it fed through to the idle jet.
After consulting youtube I could see that there was meant to be a small ball bearing hammered into this recess, mine must have corroded away and the crud was blocking the hole successfully ...until I cleaned it out. So have applied some JB weld to seal the hole and will test after it has set.
So all back to the original setup and I expect nothing will have changed in terms of running cleanly.

[themoudie]

Aye Alex,

I have the factory baseline carb settings for the 1974 250 MKIII Dellorto VHB29, but not at this time of night. I will look them out later today and post up for you and others.

The Morini had been tweaked with a larger main jet in its VHB24 and it was sh!te. Stumbling and burbling to itself! When rebuilding the carb, I reverted to the original specification and have now a lovely tan nose to the insulator.

Regards, Bill