PMA, Reg/Rec Swap Possible: Question Answered, Compatible PMA Discovered!

[T3chnic4l]

Hey, so I was able to pick up a complete PMA set up (Core, Flywheel, and Reg/Rec Combo, Whole left case side as well) from an 82 Virago XV750 for $25 from a guy who was parting the bike out, it had a screw fall into a cylinder). Ideally I would like to swap this PMA system onto my 75 XS650B, my biggest concern and question is the wiring difference. I've got stock photos to show the differences but basically the xs has more wires to the rec and fewer to the reg, and the virago reg/rec appears to be the opposite how would I manipulate my stock wiring harness to accept this new combo as well as the PMA. I've got the photos here to look at, I appreciate the help in advance. This is pretty much my last step. Once this is done I will be installing my Pamco and some cosmetic work and that's essentially it.

 

[XSLeo]

One of the things you need to check is will the XV750 rotor fit the XS650 crank. The only one I know of is the Banshee rotor. Or the new ones from HHB. You will need an adapter plate to mount the stator to the XS650 case. If the XV750 rotor fits the crank then the stator will fit under the rotor. If you need to get a Banshee type rotor the XV750 stator may not fit under it.
There is somewhere a list of suitable stators that fit under a Banshee rotor. This list tells the dimensions of the stators that fit. The inside diameter, the out side diameter and thickness.
Check these things before you get to moddinging your wiring.
Looking at your diagram the wires from the XV750 reg/rec are the three whites to the stator.
A red wire that splits and sends power through a 20 amp fuse to the battery, and power to the key switch when the PMA is putting out power. Power will flow from the battery through the fuse to the main switch to power the bike till the PMA starts to work. Just hook this red wire to the red wire in your harness that your stock rectifier hooked to.
Black to ground.
The brown is a voltage sencing wire. The reg/rec uses this tell when the battery is below 14.5 volts.
The yellow wire might be used like the yellow from your stock stator and be used to send power to the safety relay. To start I would just leave this wire unhooked. Once you get the bike running and the PMA charging check this wire for voltage. It should have no voltage when the bike isn't running but have voltage while running. If above 4.5 volts when the bike is running it can be hooked to the yellow wire of the safety relay.
I'm sure others will read this and respond also. Doing a bit of searching on PMA's on here will lead you to lots of good info.
Leo

 

[T3chnic4l]

I just thought I would mention this in case its useful to someone else. The PMA from a 1982 Virago XV750 Fits exactly, the flywheel is identical in diameter to the OEM stator on the 75 XS650B. The crankshaft hole is also identical in diameter, and if you happen to have the crankcase cover this came with it works very nicely to chop down to create a plate to mount the core, or at least for me its been easy to work with so far.

However on the rear of the Flywheel (It is on the Virago in the Reverse manner of the norm) there is gear of the same diameter that is 14mm thick and is very near to contacting the alt cover, it is secured with rivets of sorts to the flywheel, I am considering cutting these rivets, or at the very least thinning the raised edges of the gear to bring them down a bit.

When I complete my adapter plate and the conversion I will post final pictures.

 

[Marvelicious]

Hmmmm, if the flywheel taper is the same (which wouldn't surprise me at all), you could make case cover mounts for virtually any stator the right diameter. I am definitely interested, since I'm already looking for a Virago parts motor.

I'm not sure I'd get too exited about using a worn out R/R. Make the mechanics of it work, and buy a new R/R to avoid all the troubles.

 

[T3chnic4l]

I guess I'm not exactly sure what you mean by the flywheel taper, is there a minor change in diameter from the open face to the closed face? If there is something you would like measured I'm more than happy to do so for you.

I'll likely buy a new R/R my plan was to connected the system and trouble shoot as far as correct connections and such and then replace the R/R to ensure long term functionality.

I'm not sure what exactly to do though about the gear on the face of the flywheel, I worry the strength may be compromised if I simply cut the rivets and remove the gear. However I worry the minimal side cover/flywheel clearance presents the opportunity for future catastrophe, and my opportunities to manufacture a replacement alt cover of some sort is rather limited.

 

[Marvelicious]

There is a taper on the end of the crankshaft, and on the inside of the flywheel. The crankshaft taper will have to match the inside of the flywheel taper. That's why everyone wound up using the Banshee stuff, because it matches.

If that is the same, then game on!

 

[Marvelicious]

BTW, I doubt there is any strength in that gear. If memory serves, that gear is part of the starter drive - the power goes from the gear, through the rivets, to the flywheel, to the crankshaft - which means that the flywheel has to be strong enough to handle the starter torque.

Edit: To be clear, I wouldn't worry about it at all.