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Monday, May 26, 2014

Aprilia Electric Stuff (updated)

see update at the end...

My Aprilia is a 2004 RSVR Factory. This particular vintage is known to have some issues with the alternator stator and the voltage regulator. From what I have read on these bikes, they do like to occasionally burn up one or the other. I decided yesterday to take the time to check the condition of mine.

With the side panel off of the bike, the regulator is easy to get to. The connector between the stator and the regulator is called the "brown"' stuff. It has a nasty little habit of burning up due to high resistance pins inside. The previous owner had already eliminated the brown connector from this bike, choosing to solder the leads together directly. You can see where the wires come into the left side of the regulator, the connections are under the silver insulation.

With the insulation removed. Not the prettiest solder job ever, but I've seen much worse.

In order to test the output of the alternator stator, these three connections have to be cut or desoldered. The three coming from the top go to the stator in the engine. We'll be doing our test there. It's easy-peasy: start the eninge, bring RPM to 4,000,  test AC voltage between each combination of two wires. As long as you are above 60V  , you're golden.

It's hard to get a picture of a multi-meter while holding the throttle with your other hand. 70.6 V is a good reading.

With the test done, I resoldered the leads and wrapped 'em up. Not a time consuming job at all.
"Well," says you, "that's just the stator, what about the regulator?"
Checking the regulator output is simple enough. You just put a multimeter across the terminals of the battery with the bike running at 4,000 RPM. Mine had 12.53 V. I believe that might be a little low. I'm going to have to check in with the experts on that. If it is too low, I just happen to have a spare regulator that I can fit to the bike.
Why 4,000 RPM? There's a lot of factors that go into that. First and foremost is that this bike was designed by people who are a hell of a lot smarter than I am. 4,000 RPM is a good cruising speed. I imagine the stator was designed to be at ideal output at that speed. With a redline in excess of 12,000 RPM, you don't want the stator to have too high of an output at very low RPM. All of the excess current generated by the stator has to be shed off somewhere. The regulator converts the excess to heat, hence it has a giant heat sink. If you had a stator that put out 70V at 2,000 RPM, the regulator would have to shed A LOT of heat at cruising speed. As a rider and mechanic, that's all I really need to understand. After that, we would get into a lot of electrical theory that I only have a partial understanding of.

As I suspected, the 12.3V with the new regulator was low. The set point of the regulator is 14.5V...pretty obvious!
While checking the voltage output of the stator, I failed to do one check. Continuity between the stator and ground must be measured. There should be NO continuity there. Well, as it turns out, my stator was leaking to ground.
Here's how this works:
With the stator leads open, there is no load on the stator. You can do your voltage check all day long and get perfectly strong voltage readings. After the regulator is hooked up and a load is placed on the stator, it will leak some of the current directly to ground. You are basically adding another leg to the circuit. I have a new stator on the way and will be able to get this fixed soon enough.

While I was shopping for a new stator, I had a look around for a new swing arm (there is a recall on mine, but there isn't a dealer near by...and I don't feel like going to Chicago). I finally found a replacement swing arm, and that will be a fun day at the shop

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