Ducati 860 GTS 1975 - Help!

If you need technical information or help with your early crossover gearchange squarecase Ducati 860/900 engine - post your FAQs, comments & questions here.
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ROGERTHAT1
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Ducati 860 GTS 1975 - Help!

Post by ROGERTHAT1 »

Hi All, Image

I have recently acquired this gorgeous 1975 860 GTS. It's all v original, 21k, instrument binnacle needs sorting as does rubbish wiring, and aside from ripped and worn seat cover, rusted chrome and slightly rusty original rims its all there. 21k miles, which is supported by provenance etc.

I've ultra sonic cleaned the carbs, but despite spark, and the odd pffft.. nothing. Tonight I conducted a compression test tonight and saw 89 rear, 77 front, then with the oil injection trick, 91 front and rear. At this point, turning over the started motor resulted in several bangs from the rear pot and a warm header pipe.

In short, I am guessing possible leaky valves / rings etc? Any thoughts, help much appreciated. Thanks :-D
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BevHevSteve
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Re: Ducati 860 GTS 1975 - Help!

Post by BevHevSteve »

too low - check valve lash to start, then timing, carb sync etc
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ducadini
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Re: Ducati 860 GTS 1975 - Help!

Post by ducadini »

You're sure Your timing's "on the dots" ? Rather easy to check behind the covers on top of the bevels. Remember it could take some turns to align.
You're sure You plugged the correct cylinders ? Remember this engine turns backwards.
And of course : RTFM.

have fun, we did on ours

ciao
ducadini
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wdietz186
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Re: Ducati 860 GTS 1975 - Help!

Post by wdietz186 »

I suggest you start by replacing the ignition. The original Ducati Elettrotecnica[sp?] system was junk 40 yrs. ago. I would wager it's the reason the bike has such low mileage to begin with! The Sasche or Michael Arnott's Hand Held Dyno systems seem to be the way to go these days. I think the Sasche is the less expensive of the two. Relatively easy to install [with the exception of pulling off the primary gear, needs a special tool and fabricating coil mounts] they have the benefit of being better for the crankshaft life because of an actual ignition advance curve. Other than the ignition it should only need the basics to run, air fuel, and spark. The carb insulators tend to shrink and leak vacuum so it would be wise to replace them along with adjusting the valves. The original handlebar switches are junk also, replacing with most any modern switch will ensure you have lights when you need them. When it runs and the lights work you will find it a ball to ride! And you will be a member of the "Bevel" Ducati owners, much more exclusive than the Panagale crowd!
ducadini
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Re: Ducati 860 GTS 1975 - Help!

Post by ducadini »

Our experience with the old Ducati Elletronica ignition is : when it works, it works. First thing to go is the low-rev part : difficult starting because it's running on one cylinder until revs go over 2k, then the "defect" ignition kicks back in. No problem for racing :-D . The moment both low-revs are dead, You're in trouble.
Since Roger says he has sparks (You don't get that engine running over 2k on the starter alone) indicates that the low-rev is still working.
Unless the three bolts of the ignition stator are loose and changed the timing, it still should be correct.
So we suggested to check the usual stuff before spending.

ciao
ducadini
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