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Discussion Starter · #1 ·
I just replaced my stator and CDI unit (had no spark), and I’m going through and giving some love to my electrical connections, cleaning things up.
In doing so, I realize that I really don’t know what the regulator/rectifier does. I see that there are “modern” replacements; should I upgrade or wait until mine fails?
 

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Upgrades are usually a good idea if you have the budget for it. Modern units are generally better in that they cap the voltage off "more firmly" resulting in longer-lasting batteries. Additionally, modern units will usually have a lower internal resistance, allowing charging to come on sooner.

As to what an R/R does: The rectifier portion converts the power coming from the alternator from AC into DC. Your bike (with the exception of the ignition system) runs on DC power. You can run AC through some things light the head light and tail light, but stuff like the horn and flasher relays needs a definite positive and negative pole in order to function properly. The regulator portion is what ensures that the alternator doesn't put out more juice than your bike can handle. Due to Ohm's Law, as voltage increases and resistance stays the same, current increases as well. Too much current through your bulbs (and to a lesser extent your wires and fuses) and things start to evaporate. ;)

For what it's worth, we sell the upgraded parts on our website at Products
 

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....Your bike (with the exception of the ignition system) runs on DC power. You can run AC through some things light the head light and tail light, but stuff like the horn and flasher relays needs a definite positive and negative pole in order to function properly.
Good description, however your statement about the ignition system would depend on the type. A magneto ignition is AC, while a battery ignition is DC (presumably what the OP is asking about) Most trail oriented bikes from the 60's - 70's used low tension magneto's with secondary coils. Your correct in stating many of those models also had AC headlight and a tail light that had DC fed to the brake light and AC lighting the tail light.
 

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Discussion Starter · #4 ·
....Your bike (with the exception of the ignition system) runs on DC power. You can run AC through some things light the head light and tail light, but stuff like the horn and flasher relays needs a definite positive and negative pole in order to function properly.
Good description, however your statement about the ignition system would depend on the type. A magneto ignition is AC, while a battery ignition is DC (presumably what the OP is asking about) Most trail oriented bikes from the 60's - 70's used low tension magneto's with secondary coils. Your correct in stating many of those models also had AC headlight and a tail light that had DC fed to the brake light and AC lighting the tail light.
In my case, it’s a CM400C
 

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A CDI system could be either AC or DC, depending on the source used to charge the CDI (either Alternator or Battery) If it's the alternator coil charging the CDI is actually AC, but the CDI unit will only see DC because of the short time (less than a revolution) required to charge it. Not familiar with you model, so looking at a wiring diagram it appears to be an AC type.
 

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The SOHC twins are running the AC type CDI system.
If you have the budget I would recommend changing the voltage regulator to a modern version. The original unit spec was 15V +/- .5V so it wouldn't be unusual to see the battery being charged at 15.5V. This boils the water out of a standard lead/acid battery faster and is harmful to any other type of battery. I run a MOSFET type regulator on the road bike.
 

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I run a MOSFET type regulator on the road bike.
MOSFETs (especially the Series type regulators) are the best money can buy. Very good tech. We carried them for a while, but have since stopped because the market is flooded with knock offs that aren't actually MOSFET. We had to sell them at a very low price in order to move any of the inventory and it didn't end up being worth it. Almost all genuine MOSFET regulator/rectifiers are branded as Shindengen, and should be stamped with the company name and the model of the R/R. There are some genuine unstamped ones out there (they're made in Taiwan and I believe they are a supplier for Shindengen and manufactured under license), but it's not usually worth the headache to try to find an unbranded OEM part.

Honestly though, I think MOSFET is only really necessary on modern bikes that put out a lot more wattage from the alternator. The main advantage of MOSFET is its ability to handle a lot more current without overheating. On our old machines, the alternators rarely put out more than 110W (closer to 150W on the three phase twins made on/after 1978) and so modern thyristor technology (the tech we use in our R/Rs) is more than up to the task. Our R/Rs are bench specced at 13.9V, plus/minus .2V. In the real world, this puts your charging output at around 14.2, give or take a couple of tenths, so it's safe for LI-ION and also prolongs the life on your lead acid batteries as well. I know I'm in the business of selling these things, but I honestly think they're a better value part for the vintage machines.
 

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The 400/450's are rated as 170W. The road bike is running a GL1000 stator at @350W so the MOSFET is really a good thing. FH020AA and SH847 seem to be the latest versions
 

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The 400/450's are rated as 170W. The road bike is running a GL1000 stator at @350W so the MOSFET is really a good thing. FH020AA and SH847 seem to be the latest versions
SH847 is my usual recommendation for bikes that use MOSFET. They do wonders for modern Triumphs (which have a tendency to eat stators).

Also, attached is the charging output specs from the FSM for the CB450. Looks like about 130W in night time mode.
 

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