1981 XV750 Regulator/Rectifier Testing (Southeast CT)

[supercub]

Can anyone tell me how to test my regulator/rectifier? I have a Fluke multimeter. I tested my unit by the service manual and I get the opposite results of passing for continuity and discontinuity when the multimeter leads are switched from pos to neg. Also, I am not sure which scale the meter should be set to, 1X? I tested my stator and that test seems straightforward. I brought a new regulator and it also fails the test but shows no continuity in any of the tests except if I set the meter to 1000 ohms, then it shows continuity in every connection. The bike is not charging. Thanks

[ViragoJoe]

Can anyone tell me how to test my regulator/rectifier? I have a Fluke multimeter. I tested my unit by the service manual and I get the opposite results of passing for continuity and discontinuity when the multimeter leads are switched from pos to neg. Also, I am not sure which scale the meter should be set to, 1X? I tested my stator and that test seems straightforward. I brought a new regulator and it also fails the test but shows no continuity in any of the tests except if I set the meter to 1000 ohms, then it shows continuity in every connection. The bike is not charging. Thanks

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supercub,

Add your bike information to your profile "What Virago you Own:". If you open another topic and forget to mention what year and model Virago you have (Especially, if you placed this topic under: "Electrical".) it'll be located to the right in your profile information. That's where I found your location to add it to the Topic Subject Line (Southeast CT).

How To Test a 3 Phase Regulator/Rectifier: Make sure your Flute Multimeter has the "Diode Test Setting". You forgot to mention what Flute Model you own, so we couldn't verify for sure to know if you have that setting or not. You'll need to check. Let us know, so we can mark this topic (SOLVED). By way of a quick check, the Fluke meters we came across all had it.

How To Test a 3 Phase Regulator/Rectifier
https://www.youtube.com/watch?v=-2jWIkhy1fo

[supercub]

Thanks for the video. I checked my rectifier and stator and they test OK. The problem I had with testing the rectifier by the service manual was that they didnt mention to set the meter to diode and they give pass/fail criteria as continuity or discontinuity, so I was using resistance, not the diode setting. I have a Fluke 117 which has been a great meter. I will start the bike again and check for voltage coming out of the stator. It should be fine but I believe that since I am using an auto battery to run it, the battery is so large that it just shows a constant voltage from running or non running engine. Time to by a battery and test the bike out.

[ViragoJoe]

Thanks for the video. I checked my rectifier and stator and they test OK. The problem I had with testing the rectifier by the service manual was that they didnt mention to set the meter to diode and they give pass/fail criteria as continuity or discontinuity, so I was using resistance, not the diode setting. I have a Fluke 117 which has been a great meter. I will start the bike again and check for voltage coming out of the stator. It should be fine but I believe that since I am using an auto battery to run it, the battery is so large that it just shows a constant voltage from running or non running engine. Time to by a battery and test the bike out.

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supercub,
You seem to love walking a tight rope!

In an emergency you may want to use a car battery to get you started if stranded on the side of the road with the car engine not running, repeat, engine not running, when you are jump starting your Virago.

Your Virago wasn't designed to work with a battery that large. Suggest you get the appropriate WET cell or AGM (Absorbent Glass Mat) battery that is maintenance feel. Go with the AGM if your wallet can handle it.

But, never use a car battery the way you are currently. Remember Murphy's Law: "Anything that can go wrong will go wrong." That car battery can smoke your whole electrical system big time. However, if you want to take the risk and walk that tight rope, it's not my bike!

You are aware, that the voltage coming from the Stator is "AC" and not DC. Right?!
The Higher the RPM's the higher the AC (Voltage on average is 40 Volts AC, sometimes higher).

[jsyzdek]

@Supercub,

I have had an issue with the rectifier in my own Virago a while back. The battery voltage (DC voltage) that I could read on a little gizmo I mounted under my handlebars, was always oscillating wildly, and for the longest time I thought that's just how it is. Until the relatively new AGM battery went completely dead and dry. Then I went ahead and replaced both the battery, and the regulator. I mounted the regulator on a heat sink and I haven't had any electrical issues at all. The bike starts up with the battery at ~13.2V and while on idle, it climbs to a very steady 14.2V within 10-20 seconds. Then it stays pinned at 14.2-14.3, no matter the engine rpms.

I'm attaching a picture of how I mounted the regulator. On Saturday I drove the bike most of the day through winding back roads, at the end of the day my lower back was sore! The last stretch was a continuous 2.5h ride and when I got home, the heatsink was cool to touch, and so was the regulator itself, when I reached behind and touched it with bare fingers. Try that on a regulator mounted next to the exhaust can, behind the passenger foot peg. Your skin might stay on it for good.

Note: I spent $9 on this regulator on Amazon. I had the heat sink in a junk box already, from another project. So far, so good.

@Joe: I personally wouldn't be concerned about using a car battery to start/run the bike during testing. If it's a 12V battery, then it won't provide any overvoltage to the system, however, because it's higher capacity and lower internal resistance, it won't drop quite as low during the start. The voltage under load is U = E-IR, where E is the open-circuit voltage of the battery (say 12.5 to 12.9V, depending on the exact type, or state of charge), R is the resistance of the circuit, including the battery itself, the starter, wiring, relays etc., and I is the current drawn.
Typically, during an engine start, a healthy battery that is matched to the vehicle, drops from 12.5 to 10-11V for the fraction of a second it takes to start it. When the battery is weak, or the weather is cold, it may drop to 8V or less. At some point it will drop so low that the starter won't be able to produce enough power to start the engine. However, if the battery is oversized, all that may happen is that the battery will drop to 12V, or 11.5, instead of 10V. No big deal. It would be a completely different story if you connected a 24V battery...
In fact, when you run a bike, a properly working regulator should keep it at 14.2-14.5V, right? When you stop the engine, the battery voltage won't instantly drop to 12V. It takes a little while for the excess voltage (some people call it surface charge, which is a simplification, but it's OK) to dissipate. And so if you stop the engine and within a second you start it again, the battery voltage may only drop to from 14V to 13V during the start, and no Armageddon happens as a result.
You may argue, that higher voltage under load means that the drawn current will also be higher. That's true. And so the product of U*I, which is the power produced by the starter will also be higher. That is also true. However, you're more likely to stress and overheat the starter if you keep cranking the engine for 20s straight, letting the voltage drop low, and making the agony last so long, than you do by starting it within half-a second, or quarter of a second, even though it may draw 10% more power than it would on a regular battery.

[ViragoJoe]

jsyzdek,

Thanks for the battery information update, good to know.
Glad you are here. No one knows batteries better since you work with them on a daily basis.

I like your idea with the big heat sink. Here is what I did. Doesn't dissipate heat like yours will:

R-R with HEAT SINK SIDE VIEW 20171116_093057.jpg