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Discussion Starter · #1 ·
My 79 Darmah has recently developed a major backfire out of he vertical cyl. It starts great, then quarter mile down the road she backfires hard and sometimes loses the vertical all together. Then it comes back after some major backfires and runs well. But ALWAYS back fires hard on decell. It has popped so hard that the carb has almost popped off. New pistons, carb slides, rebuilt carbs....the list goes on. All work done in the last 1k miles and issue developed within the last 100 miles...... On the upside, my GTS is as reliable as a brick!
 

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Mightr be sucking air past the rubber gasket between manifold and head?

As it warms the seal may be lost.

Worth a check.
 

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Discussion Starter · #3 · (Edited)
Manifold rubbers and o rings are new as well.. I spend lots of money and endless hours in the shed . I tend to get a few hundred blissful miles before the gremlins take over..
 

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The back off banging and popping could be an air leak, but the backfiring under power then cutting out and backfiring again sounds like intermitant spark.
I don't envy you finding it cheaply.
Electricery is the hardest thing to find a fault with, especially intermitant faults.
I wish you Good luck.
Graeme
 

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Sounds like Bosch inition pickups/wiring going bad.
+1.

Check the condition of the insulation on the wires close to the pick-ups. If it's shot, there's lots of info on how to repair them on Steve Allen's Bevelheaven site.

Just be aware that re-positioning the pick-ups requires the use of the correct Ducati tool ... and a certain amount of patience :).

Ciao

Craig
 

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If your not a "keep in original type" replace the coils and pick ups my bosch units were abit sus .

invest in those o-ring intake mainfold spacers on flea bay again my original rubber iuints were a bit soft and sad


https://store.bevelheaven.com/electrics-battery-ignition/dyna-coils-5-ohm-black/

https://store.bevelheaven.com/electrics-battery-ignition/dynatek-7mm-silicone-spark-plug-wire-set/

Ducati Bevel Inlet Manifold Upgrade | eBay


shane tbird
2008 hypermotard
1982 SS
Bevelheaven also has the manifolds.
 

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Discussion Starter · #9 ·
It seems the plastic sleeve that is in the Carb mouth is worn. The one that slides over the inintake. I sealed it up but Havnt had a chance to ride it. I replaced the pick up wires a few years back. But I have a spare set of Bosch boxes. I will swap them out for good measure. The smaller ignition harness is new also. It does however retain the original coils. I plan to put my inline spark tester on it for a ride. When it cuts out I will simply look down and see if she is sparking. When all is well she rips along at full song like no other....
 

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I had a similar problem with my Darmah, you tend to expect the worst scenario when this sort of thing happens. I went through a long list of potential causes before finally discovering that the front Dellorto was leaking raw fuel into the cylinder and fouling up the plug.
An immediate remedy was as simple as remembering to turn off the fuel taps upon shut down.
 
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