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Discussion Starter #1 (Edited)
A few months back I noticed that my ST2 was cranking slower and slower. I had had the bike a few years and had no idea how old the battery was, so I figured it was at the end of its life and I replaced it. The bike cranked nicely at first and seemed to be OK, but after a few rides over a period of months the cranking started to get weak again, so I checked the battery voltage with the bike running, and I found that it was lower than I would have expected - like 12.1V or something.

So I bought a new Ducati brand R/R (ouch), installed it, ran the bike and checked the output and all seemed well. Battery voltage was a steady 13.8 with the bike running (can't remember the RPM or if I had charged the battery first).

A few hundred more miles and a few months later, and again the cranking started to get weak. I checked the RR output again, (I don't remember the actual voltages), and for whatever reason I decided that the new RR had gone bad. I tested the stator for shorts and it seemed OK, but none-the-less I ordered a stator and an RR from Electrosport. Though it was advertised as being for an ST2, the RR didn't fit the bike (it was too tall to fit in the air intake), so I had to grind about 1/4" off of the cooling fins to make it fit. I was pissed about having to do that. I complained to Electrosport, but they never answered me. I installed all of this new stuff, and I checked and cleaned all associated connectors. I checked battery voltage with the bike running, and it was 12.3V, which I thought was a bit low, but I figured the depleted battery was charging at max. I rode off the next time thinking all was well.

After a few short rides I was out one day and the dash started flashing. I know now that that was probably from low voltage, but I didn't understand it at the time. I had recently checked and cleaned all of the front harness connectors, and I thought the issue was caused by having done that. Before I got home the bike died from running off of the battery, and I had to push it the last half mile home. I cleaned all of the battery cables, charged the battery, inspected the RR cables, etc., but didn't understand to check the RR output. Hell, it was new, why should I check it? When I fired the bike up again the dash was no longer flashing (again, I didn't realize it was voltage related). I thought I had fixed the problem, so I went out for a couple of short rides over the next couple of weeks, and then the same thing happened again.

So I partially charged the battery, fired up the bike, and checked the RR output. When the bike started up I could see the battery voltage went from 11.9 to 12.1 and then slowly start to increase while idling. Over a period of about 2 minutes I saw it climb up to 12.4, so I figured that charging was OK, but then I found that when I increase RPM's beyond about 1500 the voltage actually goes down - more RPM, lower voltage.

What the heck is going on here? I saw some posts that suggested this is a battery issue, (its now a year old and it has been drained a couple of times), and others that indicate this is an RR issue. I'm getting tired of buying RRs. Maybe this one was never any good?
 

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Agree with above and also add it would be worth doing a voltage drop test. It sounds like this may be the issue.
 

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Discussion Starter #4
Thanks for the link. I have used Brad's instructions for fuel injection tuning, and so I know his stuff is spot on. I'll give it a try.
 
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