Replacement regulator/rectifier

member14827

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Has anyone had any luck replacing the stock rectifier and voltage regulator (two separate components) with one of the combination regulator rectifier units out there?

I recently replaced my voltage regulator with a BWD R296 per this thread. It worked fine for about two weeks, then the regulator failed, overcharging my battery, killing it, and killing my ignition box in the process.

Rather than replacing the regulator with another R296 and hoping it lasts longer than two weeks, I was considering replacing both the regulator and rectifier with a modern regulator rectifier. I'm presuming any unit made for the 3-phase AC input (typically three yellow or white wires) and 12-14VDC output (typ. red and green wires) should work, provided it can take the current.

Examples:
https://www.amazon.com/GooDeal-Regu...egulator&qid=1558359162&s=automotive&sr=1-173
https://www.amazon.com/dp/B07G8432BC/ref=sspa_dk_detail_4?psc=1&pd_rd_i=B07G8432BC
https://www.amazon.com/31600-463-00...regulator&qid=1558360431&s=automotive&sr=1-53

Has anyone done this on the XS400? If so, what did you use?
 
I use a R292 regulator. Splice the yellow and orange together and fit it to the connector. My bike could have slightly different wiring than yours, which came with a mechanical regulator.

It helps to put your bike info in your signature or title to keep things clarified.

What battery are you using?
 
Oops, sorry -- It's a 1980 XS400G (Special II). I was using a a small 12V alarm battery until it got cooked. Now I'm using a more traditional motorcycle battery, sealed lead acid -- a 5LBS. It's overkill, really, for what I need, but I was stranded and the Advance Auto was a few blocks away; it's what they had.

Electrical load is fairly minimal -- no starter, LEDs all around. But that new R296 regulator definitely failed. When I got home, I metered at the (new) battery with the bike running and the gen was pumping 15-16V with little revving. No wonder my lights were so bright!

Anyway, I quickly shut her off and looking at replacing the regulator and maybe the rectifier.
 
I use AGM type batteries. The smallest ones I can find at the store are 120CCA, which is just enough to get the E-start working when I need to use it.

Our bikes electrics and regulator options arent my strong subject, but I know my reg will put out 14.5v max..

I read somewhere on here that the regulator can put out much more energy depending on the bikes needs. Your battery could have had a very low charge.
 
If you have all LED lighting including the headlight you may not have enough draw on the system to balance the regulator.
I have used the R296 regulator for years on my XS650. It has the tail/brake light and turns LED but the rest is regular bulbs. I us an aftermarket headlight shell that uses H4 bulbs. The bulb is a 55/60 watt.
I went to the LED most places to help the charging system handle the bigger headlight.
Using your tiny battery may have been part of the problem. They don't hold up long on a bike. Months from what I read about.
I heard that Fiat used a similar regulator as the R296 but was smaller and cheaper. I bought a couple to test out. I now have one on the XS650. It works well and it's smaller and has a finned alloy housing. I'll have to go back through my receipts to find the cost and get the pics.
Leo
 
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That's all good info, thank you. When you say "may not have enough draw on the system to balance the regulator," are you suggesting that the regulator has an output impedance that needs to be "matched?" I suppose that makes sense; I know they'll read a lot higher output voltage if not connected to a battery, also as NewHavenMike suggested above.

I wasn't sure how the small battery was going to perform over the long term. I found recently there were a few other guys on the forum that had used those alarm batteries successfully. But again, the circuit on my bike has been so modified and uses a lot of non-stock components, it's gonna take some experimentation before I reach a steady baseline config for the bike.

I've a got combo regulator/rectifier on the way that I'm gonna try out, in a heat-sink package as you mention. I'd still be curious to know what the Fiat regulator is, if you're able to remember.
 
Did some checking. On Ebay the !979/80 Fiat 124 Spider & X1/9 VR749 regulator sells for $10.49 + $3.71 S&H. The pic has a ruler by the reg. It shows how small it is.
Easy to wire in. If you still have the stock wiring cut the plug of the old reg up close to body. On the plug you cut off, Hook the Field coil wires to the two coming from the Fiat reg. Then hook the ground wire from the plug to the body of the Fiat reg.
Then you can just plug it in.
If you have modified wiring you will need to do about the same as with stock. Just hook the field coil wires to the reg and ground the body.
O my XS650 The R296 gave me a steady 14.5 volts output. The Fiat is just a bit lower at 14.2 volts.
The 3 phase rectifier, most are rated at 1000 volts. The important rating is the amperage. The max output of your bike is somewhere around 16 amps. A 20 amp should be good to go. This size may need a bit more heat sink. The bigger ones won't be quite so particular. I wouldn't go over a 50 amp. They come in a bigger case once you get that big.
The one I use is like in the pic. You can find them on Ebay starting around a couple bucks each from China Or Hong Kong.
Them come a bit more state side.
The ones I bought the body is the heat sink, so mounting isn't quite as critical. I did see some today that had a much larger heat sink. Start around $3.58 from China.
Just search for three phase rectifier, spell out three, just 3 gets too many single phase units.
All the three phase are easy to wire in. They have three terminals along one side, these are where you hook the three wires from the stator. Maker with wavy lines. The two on the other side are positive and negative, mark + and - .
Leo
 

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Just a quick update: shortly after my original post, I purchased and installed the following regulator/rectifier:
https://www.amazon.com/GooDeal-Regu...egulator&qid=1558359162&s=automotive&sr=1-173

I've only ridden the bike a cumulative 10 miles or so since installation, but it's only putting out 12.4VDC, full load connected, while the bike's running. No increase in voltage with increase in RPM. The bike seems to run great while I'm riding, but given these numbers, I don't think this is a sustainable solution (in case someone else was thinking about trying the same thing).

XSLeo, per your suggestion, I think I'm going to try the Fiat regulator with a separate rectifier and see if I can sleep any easier.
 
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