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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Wed Jan 07, 2015 9:53 am 
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Joined: Thu Sep 20, 2012 11:48 am
Posts: 258
Location: Perth, West. Australia
model: 906 Paso
year: 1989
Might it be something as simple as the vacuum hoses from the inlet manifold to the Digiplex?

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Ducati Paso, It's an 'understanding'....


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Wed Jan 07, 2015 10:12 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5098
Location: southern Germany
model: 750 Paso
year: 1987
Quote:
I've swapped CDI boxes front to rear

indicates he has the Kokusan ignition like probably 90% of all P750s ;)
(also that would affect both cylinders)


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Thu Jan 08, 2015 9:01 pm 
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Joined: Thu Sep 20, 2012 11:48 am
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Location: Perth, West. Australia
model: 906 Paso
year: 1989
Ten points for enthusiasm?

......I know, I know.....back of the classroom.... :truck:

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Ducati Paso, It's an 'understanding'....


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Fri Jan 09, 2015 10:39 am 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
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Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
Quote:
Ten points for enthusiasm?


:thumbup: :thumbup: :beer: :beer:




Any progress Moto :?:

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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Fri Jan 09, 2015 11:53 pm 
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Joined: Wed Dec 17, 2014 12:29 am
Posts: 11
Location: US
model: 750 Paso
year: 1988
Hi,
No,Ive hit the wall. All of the components check out,voltages are equal front and rear cylinder, resistance values of the coils and triggers match.Ive replaced triggers. Ive tested and checked wiring and even jumped around the wiring harness to no avail. I tried a new coil today and it did not help. Charging system is working normally and there are no issues in the stator or wiring in that system. Ive cleaned connectors in the system as well. Ive tried 3 CDI Boxes and got a stronger spark but it still drops out above idle. Ive inspected the flywheel for any signs of damage that might interrupt a good signal from the triggers and no damage was found. I replaced the battery along the way and added grounds.......Nothing. <sigh>


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 9:26 am 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1092
Location: siena, italy
model: 750 Paso
year: 1988
Did you try to switch colis (vertical to orizontal)?
Did tou try to switch kokusan boxes?
This will allow you to find where the problem is and it will take you just some minute.

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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 9:37 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5098
Location: southern Germany
model: 750 Paso
year: 1987
Nicola, did you read this topic ?


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 11:15 am 
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Joined: Thu Sep 20, 2012 11:48 am
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Location: Perth, West. Australia
model: 906 Paso
year: 1989
paso750 wrote:
Nicola, did you read this topic ?


Probably about as much as I did...lol

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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 12:31 pm 
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paso grand pooh-bah
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Joined: Tue Jul 29, 2008 9:50 pm
Posts: 3157
Location: Hilltown,Pennsylvania
model: 906 Paso
year: 1990
Maybe its time to check the crankshaft runout ?
Wooddruff keys ?
valve timing and clearances, burnt valve ? Worn guides ?
broken piston ring..........


fuel contamination of the oil ?

Seems like you have covered the electrical issues

Just seems odd that replacing the pickup got you spark but only at idle


so if you have some spark and the fuel is OK time to check mechanical possibilities :banghead: :wacko:

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Ducati,making mechanics out of riders since 1946
There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
90 906
92 907ie


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 3:13 pm 
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Joined: Wed May 15, 2013 5:24 pm
Posts: 33
Location: USA
model: 750 Paso
year: 1988
To get us all back on the same page, when you say the spark drops above idle. Is this by using a timing light? And you said you bypassed the bike wiring harness. Did you only do that for voltage for the coil and CDI. What about the wire from the trigger to the CDI and on to the coil?


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sat Jan 10, 2015 5:37 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5098
Location: southern Germany
model: 750 Paso
year: 1987
I was also wondering, does the spark only get weaker or is it completely gone and what resistance did your pick-ups measure?


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sun Jan 11, 2015 3:07 am 
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Joined: Wed Dec 17, 2014 12:29 am
Posts: 11
Location: US
model: 750 Paso
year: 1988
Hi,
The Pick-up coils measure 99 and 99.4 ohms. the lost spark is observed by an inductive timing light and verified by a spark plug. Ive checked the flywheel and the crank there is no issues found with them. It is truely bizarre.


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Sun Jan 11, 2015 3:09 am 
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Joined: Wed Dec 17, 2014 12:29 am
Posts: 11
Location: US
model: 750 Paso
year: 1988
Hi,
When i bypassed the wiring harness, it was on Voltage, Ground and CDI to coil triger wires.


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Mon Jan 12, 2015 7:27 am 
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paso grand pooh-bah
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Joined: Sun Aug 01, 2004 12:00 am
Posts: 1092
Location: siena, italy
model: 750 Paso
year: 1988
moto319 wrote:
(The coils i have been using all pass resistance tests)...
...At this point i procured a pair of known good coils and tried them, no change...

Ok you switched Kokusan boxes... Sometimes coils can run fine at low rpm but go wrong at heavier charges.
Try to switch coil wirings (low voltage and high tension too). Switching all components from Orizontal to Vertical will let you understand which is the wrong one.

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ex...Red "smooth" 753349 :-(


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 Post subject: Re: 1988 750 Paso Loosing Spark
PostPosted: Mon Jan 12, 2015 4:16 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5098
Location: southern Germany
model: 750 Paso
year: 1987
I`m still with the pick-ups as nothing else explains the symptoms.
Meanwhile I would put my money on cable break somewhere where the wires of the pick-ups pass the engine cover (which is not uncommon). If a wire is broken either completely but still having contact or only holding together by a few strands you will still measure a correct pick-up resistance. A low voltage spark will still go through to the CDI unit letting it create a ground signal to the coil but at higher rpm the CDI unit could become "blind" due to an indistinct signal. (I have never heard of cold soldering joints at the pick-ups so I`m excluding that)

G.


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