‘78 xs650 charging system questions

[D3viousd4n]

Hey all, first time poster. I’ll try to include as much detail here as possible but if I leave something out please ask.

I’m working on replacing the single unit regulator/rectifier on my 1978 xs650 after my last one failed and overcharged the battery, blowing it up and leaving me stranded on the side of the road. This is the second reg/rec I’ve gone through in the last two years, the previous two being installed by a shop. Wanting to learn more about working on my own bike I decided to do it myself, and hoping that doing it with some love and care will keep the reg/rec lasting as long as it should.

I went ahead and bought this part (mikes xs part #24-2089) and a new battery.

The problem I ran into today is that it looks like the previous owner upgraded from the stock alternator to a PMA system. I’ve been looking at a couple wiring diagrams for this reg/rec but they’re all diagrams using the stock stator -> this after market reg/rec.

I’m wondering if I can still use this part despite the fact that it has the after market PMA system installed, and if so, how would I wire (if needed) the wires that are meant to connect to the brushes/field coils. Assuming the part is still compatible, I’d be really grateful to anyone willing to provide a more detailed description of the wiring process.

Thank you all in advance. Please reply if pictures are necessary.

 

[GLJ]

PMAs use a completely different regulator than a stock 650 charging system uses. They will not interchange. I'm sorry but I can't tell you what you need as all my 650s use stock charging systems.

 

[Jan_P]

No don't think it is possible
Different Physics as far as I know
The stock regulates the created charging
The PMA cooks it off if to big

 

[D3viousd4n]

PMAs use a completely different regulator than a stock 650 charging system uses. They will not interchange. I'm sorry but I can't tell you what you need as all my 650s use stock charging systems.

Thank you. Good news is that a PMA replacement regulator looks to be cheaper than what I originally bought anyway. I’ll try my a luck with a return request.

 

[GLJ]

Like I said I do no have a bike with a PMA. From what I have read about them and all their problems there are cheap regulators and there are good regulators. The good ones are not cheap. I have no advice as to what you should by. Hopefully someone else here will.

 

[650Skull]

This is the Reg/Rect MikesXS sells for his PMA set up.

Honestly these cheap Reg/Rect have been reported to have problems.

https://www.mikesxs.net/search?q=PMA reg rec&product_list_dir=desc&product_list_order=featured

The one you link to is for a points model bike

 

[D3viousd4n]

This is the Reg/Rect MikesXS sells for his PMA set up.

Honestly these cheap Reg/Rect have been reported to have problems.

https://www.mikesxs.net/search?q=PMA reg rec&product_list_dir=desc&product_list_order=featured

The one you link to is for a points model bike

Yeah I was looking at these. Like I mentioned I’ve gone through two of em now. I’m looking at some reg/recs that have been recommended in previous threads on this site. But also starting to wonder if I should convert back to an original style stator. Any thought on reliability between the two types? I’m running a battery anyway so battery-less doesn’t really matter to me.

 

[GLJ]

Just me but I would go with stock charging system with a @Jim rewound rotor and a bridge rectifier with a automotive regulator. Pretty bullet proof then as long as you change the brushes every 10,000 smiles or so.

 

[Its been a long time]

For quality rectifier/regulators, Shindengen is generally regarded as the gold standard. They aren't cheap. If it's cheap, it isn't genuine. It seems a lot of the stuff out there is junk.

Personally, I second what others are saying. A stock charging system with industry standard rectifier and regulator is the way to go. Cheap, proven, reliable.

From what I've seen, the PMA conversions are more trouble than they are worth on an XS650.

 

[Its been a long time]

Just me but I would go with stock charging system with a @Jim rewound rotor and a bridge rectifier with a automotive regulator. Pretty bullet proof then as long as you change the brushes every 10,000 smiles or so.

Another vote for this ^^^^^

 

[jaybar6]

those PMA's are advertised as the most powerful generators on the market, 200Watt! What is that in current?
Using the formula: power = voltage X current
rearrange the formula current = power/ voltage
current = 200W/ 12v
current = 16.66 Ampere, the solid state regulator is constantly switching 16.66A. It is going to get very hot. Therefore it wont last as long.

 

[jaybar6]

I wonder if the cooling fins are inadequate? on the rect/reg unit.

 

[Its been a long time]

those PMA's are advertised as the most powerful generators on the market, 200Watt! What is that in current?
Using the formula: power = voltage X current
rearrange the formula current = power/ voltage
current = 200W/ 12v
current = 16.66 Ampere, the solid state regulator is constantly switching 16.66A. It is going to get very hot. Therefore it wont last as long.

Indeed, if you say 100w for running the bike and the lights. That's another 100w from the PMA converted into waste heat. Think how hot a 100w incandescent light bulb got.

One of the reasons I prefer the original XS650 charging system. The other main reason is that most of the Chinesium combined rec/regs seem poor quality.

 

[jetmechmarty]

The stock alternator can generate 16 amps.

 

[Its been a long time]

The stock alternator can generate 16 amps.

Indeed it can, but only when it needs to. Not 100% of the time when the engine is running above say ~1500rpm like a PMA does.

Of course there's millions of bikes out there with PMA systems.

But the stock XS650 system is, let's say, a bit more elegant

 

[jaybar6]

the regulator is a mechanical switch (solenoid) switched at 14 volt and shuts the generator down to a lower operating state. And of course lasts for ever!

 

[jaybar6]

Yeah I was looking at these. Like I mentioned I’ve gone through two of em now. I’m looking at some reg/recs that have been recommended in previous threads on this site. But also starting to wonder if I should convert back to an original style stator. Any thought on reliability between the two types? I’m running a battery anyway so battery-less doesn’t really matter to me.

Hi D3, I wonder if the rectifier still works, but the regulator is broke? Is it possible to separate the regulator and connect/ solder, a new one on the circuit?

 

[D3viousd4n]

Hi D3, I wonder if the rectifier still works, but the regulator is broke? Is it possible to separate the regulator and connect/ solder, a new one on the circuit?

Hey Jaybar, the one on the bike now is a single unit reg/rec. I wouldn’t be able to tell ya, is there a way to test for that? I wouldn’t want to be tearing the thing apart. All I know now is that the battery is getting sent 18+ volts with just a little bit of revs.

Interestingly, I just dug out the last reg/rec the shop swapped out for me and decided to test it. Seems to pass positive/negative bias test without an issue. Starting to wonder… might try plugging that one in and seeing what happens.

 

[jaybar6]

I mean on the two rec/reg you said are toast already. you could tear one of those apart, to see the circuit and replace the reg on the board.

 

[jaybar6]

although how you get inside it, is another story!