Ducati Voltage Regulator

The voltage regulator originally fitted was a Ducati Eletronica part, and these have been the subject of many failure reports.  Some failures are simple enough - the regulator dies and the battery goes flat, the bike simply stops working.  Others are more spectacular, with reports of batteries being destroyed and even in extreme cases the electric's catching fire!  Apparently the regulator failure problem is not exclusive to Laverda - the same parts reportedly failed on Ducatis too.  The location of the regulator under the seat has an impact on cooling, apparently, which can contribute to the failure.  From Martin Damsma:-

"One of the things with these regulators is that they are in a position where they get too hot, under the tail end, no air there.  A modification Gijs van Dijk often makes (also to mine) is to put the regulator up to the front, right up in front of the cylinder heads, so that it can enjoy fresh air."

Apparently, a factory service bulletin has also pointed to a potential problem (pun intended) with the earth near the regulator.  From John Ryti:-

 "It seems the ground for near the reglator at the frame was never tightened properly, therefore causing a load on the regulator causing the early failure of said part."

Charging Rate/Electrex Regulator

The following is from Wayne Orwig, a Moto Guzzi rider/owner:-

"My regulator gave up on my 94 Cali. 1100. I must admit, I probably broke it by taking a scrub brush and soapy water to the engine to clean it up. It appears that water got between the regulator case and the epoxy. When I started the engine, it let all of the smoke out of the regulator.

"So, faced with the $200 cost of a new Ducati part, I bought an aftermarket Electrex unit. There is a little bit of difference in the connectors, so I took a small amount of rewiring. Other then that, installation went well.

"I have seen reports that these units are much more efficient, and being a skeptic, I generally ignored them. After all, the power comes from the windings not the regulator. But I was surprised and I now understand the difference. The Ducati system uses a permanent magnet, so it is always putting out power. It is up to the regulator to switch off the output when the battery is charged. The Ducati regulator uses a series thyristor for rectification and control, that has a lot of loss. Most systems, including the Electrex replacement use simple diodes for rectification that has much lower loss. They put thyristors across the alternator to short it out when the battery voltage is high enough. I have to assume that the alternator coils won't overheat.

"What it means is, now, on low beam, my battery appears to start charging before it get to 2000 rpm. It used to be closer to 2500. On high beam with driving lights, I am getting a charge before 2500 rpm. It used to be over 3000 rpm. Since I didn't know this was going to happen, I didn't get any before and after measurements, so it is seat of the pants numbers, but it certainly looks like charging takes place about 500 rpm lower.

"So, if you have a regulator problem, or your bike has lights all over it and belongs in a parade, you may want to consider an Electrex regulator.

"One other thing. The coating on the regulator appears to be softer then the Ducati regulator. Maybe it won't crack and let water in like the old one did."

Note that Electrex lists the same part number, RR51, for both the Cailfornia 1100 and the Laverda 650/668 models on their web site.

Replacement Kit

The factory can supply a complete replacement kit which includes a Nisho IWAI part.  The 750 S parts manual (the early 750 bikes being fitted with the same Ducati regulator) lists this kit as part 019 001 000078.  If your bike is still within the warranty period you may be able to get the replacement kit supplied prior to component failure.  Otherwise, you may want to obtain and fit the replacement regulator before there is a failure.  Of course, not all bikes fitted with the Ducati regulators experience a failure, with many bikes still running very happily with no changes made.


© Steve Carr, 2001-2007

Site created February, 2000.  Last modified Friday, May 15, 2009

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Last updated
30 May 2005