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Old 05-Mar-2006, 03:16 AM
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CipiVTS CipiVTS is offline
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916 Electric problem! HELP (ignition system explained)

Hi all,

I have a Ducati 916, 1995.

2 weeks ago i was driving my Ducati and suddenly it started to misfire, wouldn't rev over 3000rpm and finaly engine stopped.

checked at service and noticed that a connector from the 2 wired alternator to the regulator was melted, so it didn't charge and finally the battery was drained.

Fixed the wires and it went ok.

I remembered in the last weeks before the incident the bike's acceleration was poor/harsh (seemed like the spark was not strong enough to ignite all the mixture). Finally realized why.

So after fixing the wires we checked the voltage of the alternator and it was really bellow the standard data:

1500rpm 25V instead of min 35V
3000rpm 50v instead of min 75v
and 6000rpm 85V instead of min 140V

Also the regulated voltage was bellow 13V (recommened is between 13.5V and 15.5V)
With the main light on the voltage went bellow 12V

So the next day i changed the battery with a new one and the readings improved a bit, but still bellow accepted ones.

I also realized the misfire while accelerating was not so strong as before and the engine reved smoother throught the range.

WE measured the stator's resistance and we noticed both yellow wires ahd resistance with the ground (so something must have been wrong with the stator)

Replaced the stator with another used one, and checked the readings again.

Nor ground resistance so the stator must have been ok, but the alternative voltage reading are pretty much the same with the previous one. The only thing that changed was the regulated voltage which is now 13.6V at idle and 14.0 V while revving. The rev increase is realy smooth in all gears and the bike runs very well in all gears.

The only problem is when i turn the main beam on and suddenly the regulated voltage (measured at the battery) drops to 12.3V. If the fan starts it even goes bello 12v. If i rev it a bit it jumps to 13.3v

Driving with the lights you can really feel a differnce vs without. Harshness and misfire appears again while accelerating.

So in this case, can anybody give me any advice what do i have to replace?

Is this normal to have this regulated low voltage? Is because of the regulator unit being faulty? Or is it because of the generator's stator or rotor being damaged ?(and that's why the low alternative voltage readings)

Please help... 1 generator costs ~400 EUR and 1 Regulator is ~220 EUR. Is it worth it that i should buy both?


Please hel
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Old 05-Mar-2006, 07:28 AM
KeefyB KeefyB is offline
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It does sound as if the regulator could be faulty.
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Old 05-Mar-2006, 08:45 AM
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CipiVTS CipiVTS is offline
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This would be great...

But couldn't also be the alternator that is performing under minimum requirements and because of that the regulator cannot hold the current with the lights on?

what do you think of an aftermarket regulator like Electrix?

Can i fit the newer 916/748 3 way alternator to this engine (newer stator/rotor, newer left engine cover) + the newer regulator?
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Old 05-Mar-2006, 08:53 AM
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check also the rest of the wiring near the regulator. The two yellow wires are the common culprits, but the small loom that sits down there could be toast to.
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Old 05-Mar-2006, 09:07 AM
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CipiVTS CipiVTS is offline
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Sorry it was Electrex http://www.electrexworld.co.uk/

I checked the wiring in that area and it seems fine. What can be the symptom of a damadged loom, current loss?
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Old 05-Mar-2006, 11:10 AM
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As Nelly says check the two yellow wires futher back, on my 748 I spent a bit of time choping the bullet connectors off the wiring from the engine and replacing them as well as replacing the two yellow wires that run between them and the plastic block connector that connects them to the reg/rec.

Also consider replacing the fuel filter if it hasn't been done for a while, as when it starts to block up it loads the fuel pump more which then draws more current and with the single phase alternator models their is only so much current to go around.
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Old 05-Mar-2006, 12:18 PM
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keith_mann1959 keith_mann1959 is offline
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Hi CipiVTS
I have a Genuine ( later version )2 wire regulator thats never been used, had it as a spare for years.
45 if that helps you.
U2U if interested
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Old 05-Mar-2006, 12:35 PM
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chrisw chrisw is offline
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This article might help

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Old 05-Mar-2006, 07:11 PM
KeefyB KeefyB is offline
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Was'nt there something on early bikes where the rubber clips that held the relays near the battery actually conducted electricity?
Just a thought.
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Old 08-Mar-2006, 08:07 PM
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Hmmm this is an area i am well versed in with 2 failures of the same in 3 years and 20k miles.
Firstly i put money on the rectifier being toast.
Secondly, the 2 wires that run across the motor between the gene and rectifier i also put money on are brown and brittle
Thirdly i also bet the sub loom near the rectifier is also not exactly Y reg if you catch my drift.

The sub loom is cheap drom ducati / nelly etc etc, around 30 quid if i remember last time i bought one

The 2 wires from the gene, best way to do this is to remove the gene and get tested, and then upgrade the wiring from the gene itself with a heavier cable, or at least 1 more length of the same.

Snip the bullets off between, and either use a high quality connector block which is not only tight (loose fittings increase heat and cause failure) but also capable of handling extra current draw, and same on the new sub loom. or better still solder them together.

I ride all the time with my lights on, and i could be wrong here but little things like lower wattage indicators, and LED tail lights will help matters just a tad and could make all the difference.
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