Voltage regulator alternative?

Pat D

XS650 Addict
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Joppa, MD
First, kudos to all who give so generously of their time and expertise on this forum. Unlike social media, this platform seems to support a certain level of professionalism and fact based, data driven information that is very hard to find in many forums. The technical writing and general acumen here rates 5 stars, so thanks! Now- on to the matter at hand. I'm sorting out a potential charging issue on my stock '74, and after much research and reading determined that I may as well give the VR115 install a try. Interestingly enough, my stock mechanical regulator does not have an adjustment screw, so altering the point gaps involves bending- not the most precise. However, the VR115 is no longer the $20 referenced in the threads from 2011! More like $35-$45. OK, inflation, I get it. But- I recalled an issue I had with a mid 80's Mercury outboard, 115hp, a few years back. Mercury at that time did not provide any voltage regulation in their charging systems. They were low power, 16 amp max, and used the battery itself as a bit of a sink/sump to absorb overvoltage. The issue became modern electronics like GPS chartplotters/depth finders that DID NOT LIKE seeing those voltages over 15. So- the smart folks in the old Mercury community (much like the smart folks here) figured out that the following voltage regulator could be wired into the system and work just fine, keeping max voltage below 14.5. I did it on my motor with excellent results. This unit is only $20 now, 1/2 the cost of the VR115. I know the loads on my boat were similar or greater than what the bike sees- any reason this unit wouldn't work on the bike? Link below. There are quite a few solid state VR's out there for various applications- at the end of the day, they do the same thing- maybe there are other options to the VR115? PS- someone mentioned in an old thread that the VR115 was from '71 AMC applications and replaced the old mechanical style- I can say with certainty that AMC used Motorola solid state VR's as far back as '66, possibly earlier. Thanks for any learned thoughts on the regulator choices.


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Automotive charging systems like the one used on our 650s generally use one of two different types of regulators, depending how the brushes are wired. They are called an "A" type and a "B" type. The "A" type supplies a regulated ground signal to the brush it's connected to. The "B" type supplies regulated power to it's brush. Your '74 needs a "B" type. You would need to determine what type of regulator that outboard motor one is. The auction doesn't say. Also, most of the auctions for it list it as a regulator/rectifier. You don't want that, you just want a regulator.
That's a shunt type regulator you linked to on Ebay. Yeah, it's a reg/rec but it's for a PMA type charging system... a regulator that shunts excess power to ground to maintain voltage.
You need a regulator that controls the rotors field strength.
OK, that all makes sense- and the PMA tip hit home, pretty much any system that uses magnets in the flywheel is a PMA, which covers the older outboard scenario. I'm still sorting things out, I can't say 100% what the failure was yet- bike just shut down 1/4 mile from the driveway. I assumed it was the fuse, but after that tested good I checked the battery with my meter and got 12.7V but couldn't get an arc across the terminals. An hour on the charger and life came back to the bike. Assumption is the battery collapsed, hence the charging troubleshooting. After cleaning the slip rings, attempting to adjust the regulator, and verifying the brushes are OK, I get to about 13.6 at 3500-4000 rpm (I rarely run that high- I putt). Just took the battery off a 6 hour charge, we'll see where it is in the morning, and go from there. It's only 7 months old, and was on and off a trickle charger off season. I'd like to see 14.2-14.5 at 3000. That may not be obtainable with the stock system and the headlight/taillight on.
I have voltmeters on both of mine and don't really see any difference in voltage output when revved whether the headlight/tail light is on or off. At idle though, switch them on and the voltage output takes a pretty big hit (nearly a volt). If your regulator is original, it should have two adjustment screws for the gaps and a 3rd for setting the output .....

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I'm going to guess that the "stock" VR was replaced at some point as mine does not have any of the adjustment screws shown in either my manual or 5twins pic. This bike was not "loved" prior to me getting it, the harness had been butchered, it had been laid down at some point, and the handlebar switches had been replaced (harnesses from my switches do not match the schematic colors for '74- had to trace them out to ID). EDIT- after sitting overnight off the charger, battery is sitting at 12.7, which seems reasonable to me based on experience. I'll see if it loses anymore over the day today.


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If that is the regulator which it probably is ..
I believe you will be better off trying an electronic automotive regulator.
I tried with 3 stock regulators ( Having all screws in Place ) getting one to work Some years ago ---Failed
And i did not notice it before I put a Voltmeter on the bike
Warm days on highway speed it sometimes overcharged Which is not good for other parts on the bike .
?? 4 wires ?? Bosch type which I use have 3 pin and I believe the stock mechanical have 3
? for control lamp ????