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Hi,
I've just acquired a 1975 Ducati 860 GT. It belongs to a friend that can no longer ride. I've been asked to try to get it running so we can get a good price on a sale. Or, I might buy it for myself!

First goal: Get it to run.
What I've done.

Compression test. Max compression I've been able to get is about 70 psi on one cylinder. Applied air pressure to cylinders and found that both exhaust valves are leaking. Valve rocker adjusters loose. Exhaust valves do close more under pressure but still leak. If I get the bike running, maybe the valves will reseat?

No Spark: Bike has "Ducati Electronica" ignition system. It appears to me that I should be able to get spark even without a battery connected. I've disconnected the green wires from the engine stop diode board. Still no spark. I connected a meter to the ignition wires from the stator and do get a voltage bump when engine rotated. I'm going to do resistance checks of the stator next.

Question: Should I attempt to restore the original ignition system or proceed with an aftermarket solution? If aftermarket is advised, what should I use? I've browsed the forums and the information I'm finding is old and some vendor links don't work. I'm assuming that the ignition transducers will be replaced with coils and a battery will be necessary for the ignition to work.

Thanks,
Mike W.
 

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Discussion Starter #2
Resistance results

Checked ignition stator resistances.

Vertical Cylinder. Green-White 263 ohms. Green-Red 1124 ohms. Red-White 1474 ohms.

Horizontal Cylinder. Green-White 263 ohms. Green-Red infinite. Red-White infinite.

No shorts to ground.

Looks like I have a bad stator.

Alternator-2 wire. 2.3 ohms. Can get about 5 VAC when kicking.
 

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Hi,

What I can tell you is that those ignitions were notoriously unreliable even when new; after 40 years, who knows. I would junk the lot and fit a Sachse system.
 

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How many miles on the bike? I would remove the heads and barrels and give the piston tops, chambers and ports a good clean. These bikes were prone to leaky valve guides which leads to grubby valves and valve seats; these valve guides should have O ring seals but also look for external rubber seals as these may have been fitted. The little O rings go hard as rock and fail to seal so it's a good idea to replace them (a tricky job; just have a beer handy). Otherwise, working on these heads is relatively easy; I'd remove the valves, clean everything, re-lap the valve seats and see how this works first. If the valves are clearly, really loose in the stems then you may need to replace the stems.

If you've not worked on these engines before, remove the front head and barrel first then remove the upper rear engine mounting bolts and loosen the lower rear engine bolt. Use the front barrel hole as a handle, remove the front engine mount bolt and gently drop the front end of the motor onto a padded block; be careful not to stress the fins on the casing under the front barrel hole. Then remove the rear head and barrel. If you are lucky, the heads and barrels will pull off easily; sometimes the barrels stick to the studs if they get rusty. Sometimes the barrel and head will try to pull off as one; I use a big flat tire iron to very gently pry the head from the barrel.

This site is your friend for working out what's what: https://www.ducaticlassics.com/parts/860-gte-and-gts/all
 

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If the bike has been sitting, It could be rust/corrosion on the valve seats holding the valves off the seats. Running could knock or burn it off but the best course of action would be to pull the heads and disassemble. You will almost certainly find worn valve guides unless they were done already. With the ignition, what Duccout said is true, they were shit when new and unlike wine they don't improve with age. Fitting the Sasche isn't hard but it will require a special puller to remove the flywheel. Sometimes you can get sort of a spark by closing the plug gap down to about .010" but I wouldn't get your hopes up. If you do decide to get into it, a good manual is essential and bevel parts aren't cheap or really plentiful. That said, when they are running well they are fun and torquey to ride and handle pretty well. Many people were/are put off by the styling but I think they look cool and were years ahead of their time.
 

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I was wondering how your progress on the ignition issue is going.
Have a 75 860GT with the same conditions you described.
I get small voltage spikes on the stator output wires but no spart at spark plugs.
 

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The stator wires aren't connected to the ignition system in any way. The 860 ignition is supposedly self generating [magneto] but it is very rare to see a working one these days. Even if it did work I would hesitate to ride the bike any farther from home than I would be willing to walk.
 

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The stator is not supposed to be "connected" to the ignition system; the alternator's job is to charge the battery and power the bike via the regulator. Running the bike without a battery is not a good idea. The ignition system on the 860GT has an ignition generator that generates current to feed the two transducers. As you state earlier, if the motor is spinning, it will generate sparks independent from the battery as long as the engine stop relay in the headlamp shell is open. It may be that the relay is not working properly or the contacts in the right side switch are shorted; i.e. the engine kill switch looks open but is actually closed.

One way to check is to unplug the big, 15 wire connector block on the harness; this will break any connection between the kill switch relay and the transducers. Make sure that the transducer grounds are good; test them! It's a good practice not to trust anything by eye with these old electrics. I have an old analog multimeter withe a continuity test buzzer; best thing for this sort of work.

Do you have the wiring diagram?
 

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I just looked in my old GT860 Haynes Manual. The picture you show of the headlamp innards shows the old, engine stop device, the crappy looking circuit board with the resistor and two diodes. In 1977, the manual stated that this was unreliable and that there was a new Ducati part, the relay I mentioned above that you don't have!

If it is useful to you, I can scan some pages for you.
 

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The problem with the old stop relays was the diodes didn't. The symptom was you couldn't stop the engine. With the original ign. it takes care of that itself, when they don't produce a spark you don't need the stop device. With the replacement Sasche system power to the ign. is supplied through the ign. switch.
 
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