Matt's Moto Pages

Ducati Stator Info Page!!

Just when you thought it was safe to own a Ducati...

Before starting any Ducati repair, it is imperative to have plenty of espresso. This is important as any repair job that should take you two hours will invariably take at least six. Two shots of espresso should be taken for every time someone asks you if you are done yet.

Oh, and you should be using Illy Espresso. "Illy" is an Italian word for "don't bother me, I'm having my coffee", dontchaknow...

I've learned about as much as I want to know about Ducati engineering, luckily there are others who have pushed on further and reported back their findings. One such fearless explorer is Larry Kelly, whose email to the Ducati List with lots of info is reproduced here by permission.

I also rely heavily on my Haynes 916/996/748 manual for guidance. If you have only one workshop manual, get this one. However I also have a factory manual which is helpful for confirmation of info, and goofy Italian/English translations.

Below are photos from my recent replacement and rewiring of the stator on my Ducati 916. I found the wires going to my stator were fried, and decided to beef up the replacement (used) stator with better wires. Either I did an inadequate job in re-wiring, or the replacement stator was bad, but as of this writing I'm only getting 8volts at 3k RPM out of my Electrex voltage regulator. I will soon be diving back into the engine to fit another stator, hopefully with the results intended.

March 2003

UPDATE, Sunday March 16. After replacing the stator again with another that I was assured would work, I again got only 50 volts AC at the wires. After much head scratching I swapped the voltage regulator back to the stock Ducati unit. Presto! Holy crap, look at the power! It works! So I'm back on the road and a happy camper. I also installed the Allied Electronics volt meter recommended in Rich's email, so I can keep an eye on the System. I have also upgraded to the "NEW" Ducati voltage regulator that started showing up on Ducks since the late '90s. I've been told that these are much better and more efficient, but who knows?

Here is my page showing the new volt meter installed on my Ducati: Volt Meter Page.

Old stator with fried wires. This condition is very common, and should serve as a warning to those 916 owners who are choosing to ignore this engineering oversight. Replacement stator with new wires and heat-shrink tubing. Note that this stator did not provide enough juice and is scheduled for replacement...

Another photo of the new wires in the replacement stator. The Ducati two wire stator is meant to have .2-.4 ohms of resistance, and put out at least 70 volts AC at 3,000 rpm. This one only put out 50 volts AC, which ends up being about 8 volts DC at the output from the Electrex voltage regulator. Not enough, so out it will come.

Note: as stated above, it seems that 50v AC IS enough, but the voltage regulator was fried. Strange that the manual states very clearly that there must be at LEAST 70v AC. Maybe having upgraded wires and a new-model voltage regulator helps here.
Here is the engine with the left side engine cover off. Both oil and radiator fluid need to be drained for this procedure. The nut at the center of the stator magnet is meant to be checked on early 916's at every major service!! The spec. is something like 80 lbs. torque. I put the bike in gear and stomped on the rear brake, and could only get the torque wrench to read up to 60 lbs. before it started moving (I'll check this again when I go back in here). It had not come loose at all , so I let it go at that. The worst thing that can happen is this nut comes loose and destroys the stator and some other stuff. This was the first thing I thought had gone wrong, and was relieved to find it was all OK.
Here is the puller I made to get the left side engine cover off. It is described in detail in the Haynes manual, which you really must have to do all this stuff. Using the left inspection cover as a template, drill a thick piece of steel material. Screw the correct size bolt into the crank end through the inspection hole, and screw the plate down on top of the bolt. This pulls the case away from the engine. Light tapping with a soft mallet helps the process along. Make sure you use thick enough steel for the puller, this one actually bent.

This is a rather vital little tool. It is a scrap piece of cardboard employed in holding the engine case screws in order and off the floor. This is time well spent, as putting it all back together goes smoothly and you don't accidentally put that 2" screw into a 1" hole and crack the cases.

Here are my tools I use for soldering. I'm still not very good, but the connections stay connected at least. The important things here are a powerful instant-on soldering iron that can heat up heavy gauge wire and the solder for good connections (with a good tip, this tip is done and has been replaced). Also here is soldering iron tip cleaner and tinner, important to keep the tip in good shape. The flux in the white tin is vital, don't expect "rosin core" solder to do the job, it isn't good enough by itself. Use flux on every connection. This is plumbers flux, it says "not for electronics", ignore that. I have it on good authority that it doesn't matter. NOTE: I HAVE SINCE FOUND THAT THIS STUFF CORRODES THE COPPER WIRING TOO MUCH, SO I NOW USE REGULAR FLUX PASTE FROM RADIO SHACK. Heat shrink tubing is the only way to go in making things neat and clean. I dislike using electrical tape as it almost always peals off especially around heat. I haven't tried the brush-on type of coating yet, but it is on the list to try.

The other thing I've started using is dialectric grease for all connections. Also called "tune up grease" it is typically used in spark plug boots for better non-sparking connections. I found that all the grounding connections had corroded and needed cleaning and re-soldering. Available at auto parts stores.
This Wurth parts cleaner spray is the best stuff I have ever found to de-grease parts and clean off surfaces. If you have ever used "contact cleaner", you might have been surpised at how it ruins paint, plastic, and rubber. This stuff is totally safe on all those, and cleans just as well. Very hard to find, I have to go to a dealer in town and ask the service dept. to sell me some. If you ask any mechanic they will swear by this stuff.

Conclusion: So my Ducati works great now. It has the original Ducati voltage regulator installed, awaiting the outcome of further testing of my Electrex unit. When I ride the bike the volt meter shows me how well the System is working, so I have some peace of mind knowing everything is OK. I came home the other night and had a surprise when I plugged in my battery tender to charge the battery- the green light came on right away! That signifies that the battery was already at full charge, something it was never able to do before. I attribute this to the fact that the charging system wires were breaking down from the beginning, plus the grounding connections were terrible. By upgrading the connections and wires it seems that I have solved much of the problem with this System. NOTE: I HAVE ALSO REPLACED THE STARTER CABLES WITH VERY THICK HEAVY GAUGE WIRES, WHICH HELPS THE STARTER TO SPIN OVER AND REDUCES THE DRAW FROM THE BATTERY. EVERY BIT HELPS.

March 20, 2003
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