Richard's ST2 pages - voltage regulator

Information on this page last updated 6/9/06.

If you talk to many Ducati owners or read the mailing lists you will relize that there have been quite a few instances of failed voltage regulators on 1990's Ducatis. My stock regulator has yet to fail, although I have used it on and off along with a series of Electrex regulators.

A friend had his stock regulator and an Electrex RR51 fail and has tried the updated Ducati regulator. He says it looks identical to the old Ducati part but the dealer claimed it is revised internally. Has been working fine for him and he says it has higher output at low RPMs than either the original Ducati regulator or the RR51.

Note that the regulator may work intermittantly, the above mentioned friend had this happen on his ST2. Charging system would check out fine in the driveway but battery was not staying charged during a ride. He hooked up a voltmeter and put it in his tank bag where he could see it while riding. Bike would charge for a while but after riding for a short while it would start to discharge. Replacing the regulator cured this problem.

To date I have been through three Electrex RR51 regulators. I tried them not because the stock regulator failed, but rather as a pre-emptive strike to hopefully avoid being stranded with a failed regulator. The RR51 has the reputation on bikes other than the ST2 for being very reliable. However, I have had three fail on my ST2 and I have heard from several others that have had one or more RR51s fail on their ST2s.

2005 update - Apparently Electrex is now ElectroSport, their Ducati regulators are listed here. The model number for the early ST2 application is now ESr500 instead of the old RR51. I have no experience with these and do not know if they are the same as the old Electrx units or different.

2006 update - My stock regulator is still working fine. One of the reasons may be that when I last removed it I used some heat transfer paste when reinstalling. Another reader of this site just reminded me of that, he used heat transfer paste when replacing his regulator with a stock Ducati piece. His has been working fine for 3 years. The idea is that the paste will improve heat transfer between the regulator and the headlight surround it is mounted on. This will keep the regulator cooler and it seems to help with reliability. You can find the paste at most electronics shops and some computer shops as well.

Another option here, taking the above idea a bit further, is to relocate the regulator to get more airflow over it. Charlie at Procutting sells a heat sink just for this purpose. It relocates the regulator to the lower triple clamp area and is vented to improve heat dissipation.

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