Hay everyone. I am new to Ducati and don't currently own one but am just finishing restoring a 1977 900SS for a customer. I have a question for the group. The bike has about 7,000 miles from new, one owner. Last started about 25 years ago. I have gone through and done a cosmetic restoration -- new frame and body paint, new plating, chrome and zinc, wheels rebuilt and polished, ss spokes, gauges rebuilt everything tidied up. I used as much of the original chrome as possible. Only the motor side covers were removed to polish. Carbs and breaks completely rebuilt. Ran when last parked. And yes before you ask, all ground connections have had the paint removed and dielectric grease applied to all frame points. Now the problem: It won't start. I have spark, fuel looks good at carbs. Electronic ignition. Do the spark plug wires have to from a dedicated coil or could the wires go to either plug? Help, Thank you. George gekrestorations.com View attachment 198553
It has 2 independent ignition systems, one for the horizontal cylinder and one for the vertical. It won't run if they are the wrong way round. You may have to track back to which ignition unit is connected to which pickup. I have the info somewhere.
Thanks Derek, that's what I was suspecting. I have tried swapping plug wire without success. How does one determine which coil goes with which cylinder. that is the question.
Also worth looking at your starting process... 1) Fuel taps on, left and right. 2) Tickle the carbs, depress and hold the plunger until fuel runs from each carb. 3) Give the engine a few gentle turns over to get things moving, 2 or 3 rotations with IGNITION off and get the rear cylinder on compression 4) Ignition on 5) Nice firm kick (sturdy boots on) and twist the throttle a bit as you go and get your foot out of the way pronto Any joy?
Yes, it's the same process with British vertical twins which is what I usually restore. Everything I know about this setup tells me it should start. I am looking for the nu-ovious answer. Thanks for the tips though. No joy until I hear it fire.
Might be really worth giving the carbs a good tickle, opening throttle a couple of times, turning the engine and getting it primed on the rear cylinder before giving it the old heave-ho... my MHR can sometimes demand that of me after a rest. Usually fires up first or second kick but I've had days where it has made me work for it.
If you have good compression and fresh petrol, then it must be either no spark or sparking at the wrong time. Dunno what they exact setting is but it will be just before TDC. Is it correct for both cylinders?
No Start yet. "Have you got good compression?" Yes "Otherwise no spark or sparking at he wrong time." ? (I have spark but I don't know when) "Is the petrol fresh?" Yes
Does it have electronic ignition that works off points or fully electronic? If it works off points, it should be possible to determine the timing with a test light.
This a 1977 bike which I'm pretty sure had the Ducati CDI electronic ignition as fitted to the GTS. The Bosch ignition was first on the Darmah when it came out in 1977 and then to the SS for 1978. Only the 750's had points. If there are sparks there is not much you can get wrong timing wise with the CDI units apart from having the plugs on the wrong cylinders.
Would turning the engine over slowly produce a spark that might indicate if it is firing at or around tdc for that cylinder by poking a screwdriver down t’t plughole??
I doubt it. I'd think it would enough speed for the pickup to generate a pulse that would trigger the CDI.
