Late model regulator/rectifier on a 79?

CrubHunter · New Member Joined: Nov 01, 2009 Posts: 5

OK guys here goes. I did some poking around and I can't find any info on this if I missed it please point me to the thread. I just picked up a 79 special, runs but will not charge. somone at some point has removed the seperate regulator and rectifier and installed a reg/rec from a 80 and up bike. They removed the plugs and installed the 8 way connector for the later part. As far as I can tell the rest of the charging system is stock (I hope). It looks like the rectifier is working, when I jump battery voltage to the postive brush the alternator will put out 14-15 volts with the engine running.

I think that I should get battery voltage to the postive brush with the key on, correct? When I check at my reg/rec conector I have battery voltage at the red wire, a good ground at the black wire and with the key on I have battery voltage on the brown wire, but less than 1v on the green wire to the brush. I think that the regualtor portion of the reg/rec is bad. I substituted a reg/rec from my buddys bike to test, and had the same result. But the other bike does not charge either so I don't know if his reg/rec is good.

Has anybody had any experience with this situation? I know the stators are different for the late and early bikes but the difference is in the markings for the ignition? from the wiring diagram it looks like the systems are wired the same. Thanks in advance for any help with this.

pamcopete

CrubHunter,

The eaqrly bikes '71 to '79 have one brush grounded. The regulator suppplies switched battery to the other brush.

On later bikes, '80 to '83, one brush is connected to battery and the regulator provides a switched ground to the other brush.

In order to use a later reg/rect on an earlier model, you have to isolate the grounded brush with three nylon swcrews and wire battery from the ignition switch to the brush.

CrubHunter · New Member Joined: Nov 01, 2009 Posts: 5

Thanks for the info. When I looked at the Clymer manual that I am using it shows the black brush wire as grouned for all 80-81 bikes hence my confusion.

Next I got nylon screws for the negitve brush. They are 4mm correct? The ones I could find today were not marked but I think they may have been 6-32. With the brush un-grouned, I supplied battery voltage to it with a jumper wire from the alternator harness to battery voltage. With the engine running found voltage still low. Substiuted the borrowed reg/rec and found the battery charging only at 12.3-12.6v with the engine running even at 3500 rpm. It was producing enough voltage to turn on the headlamp. Then I jumped the green wire from the regulator to ground with engine running and had over 14v. Now it looks like I have 2 bad regulator/rectifiers? I appreciate any ideas, I just want make sure everything is correct before I buy and install a new reg/rec.

CrubHunter · New Member Joined: Nov 01, 2009 Posts: 5

I installed a different used reg/rec and rechecked. Now the bike is charging at 13.5-13.8 volts. I know it is a little low but at least I know that the sysem is wired correctly. I will re-wire the bike during my build but I wanted to figure this out first. Now on to the carbs!

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