Hi
I have been having a problem with a bike I recently purchased. It is a 1986 FXRS mostly stock, aftermarket exhaust and possibly a cam.

The problem is: with the voltage regulator plugged in, it will not run right. If I unplug the VR from the primary or the main breaker it starts and runs perfect. Plug it in and it sputters, rough idles, backfires, and will die.

I have run through the tests outlined in the manual (the same as the sticky here in the forum). Stator passes the test, I have had the battery load tested and it is good, changed the main breaker, and the VR (2X).

I have run through the wiring and found a couple "Ahh ha" loose grounds and corroded wires but even after fixing these up the problem persists.

I have had it running fantastic a couple times, but when I try to start it later it wont run right. I am out of ideas and any help would be much appreciated.

Thanks,

Colin

 

Maybe something shorting out partially in the stator plug where the VR connects at the primary? You unplug it and it works ok. You plug in the reg, or another reg, and it runs rough due to short?
Or an intermittent short in the stator itself?
You might have to open the primary and have a look for scorched wires etc.

 

Have you tried Dr. Hess's checking your charging system sticky?

 

I had the same problem a few years ago...I used to run a plug on my voltage regulator wire to the battery so that when I replaced the voltage regulator I didn't have to fish the wire out all the way to the battery.
Lots of guys in the bay area did that because it's a pain in the *** to have to get that wire out every time a voltage regulator fails.

Doing that worked just fine and was convenient as hell until the wire got old enough to start giving problems....There were multiple bare spots that were grounding out and a couple of spots where the wire was just about to break.
I removed the wire and stopped running it that way and the problem ceased.

Even if you don't run it the way I ran mine, you probably have a slight grounding problem somewhere in that wire...Not enough to be a dead short and shut the bike down but just enough to cause the problem you describe.


Or not.....

 

Did you do the AC check?

 

One time I found the coil overheated do to a bad ground put a new one on, fixed the wires and everything was fine.

 

Since you have done the test,(I actually read his post), isolate the wire going from the battery to the regulator...check it with a meter to ground...bet you got a short in there somewhere.

 

Thanks for the replies guys I knew by putting this out in the community someone would have some ideas.

Hopper, I thought of the stator plug causing the problem and so cleaned it up (oily) and tested with it pushed in, pulled out, and places in between. It passes the test every time for a short in the winding and for AC output.

Texashillcountry & Dr. Hess, yes I have run through the tests described in the sticky and also any of those described in the service manual (that don't require a special jumper wire) everything tests as it should, battery, stator, resistance, output, all within specs.

Greezeyrider, when I pulled the first VR off the bike I found possibly what you are describing. That was one of those "AHA" moments because the connection was corroded. I replaced the VR with a solid wire from the VR to the BAT.

Touchdown, I have tested the coil per the manual and it also passes.

Tom84FXST, I thought of that yesterday when I put on the new VR from Harley, I tested that wire with the ohmmeter and visually and it looks good.

All these replies make me feel like I am on the right track as these are the things I thought of initially. We need to dig a little deeper...

 

Thanks for the replies guys I knew by putting this out in the community someone would have some ideas.

Hopper, I thought of the stator plug causing the problem and so cleaned it up (oily) and tested with it pushed in, pulled out, and places in between. It passes the test every time for a short in the winding and for AC output.

Texashillcountry & Dr. Hess, yes I have run through the tests described in the sticky and also any of those described in the service manual (that don't require a special jumper wire) everything tests as it should, battery, stator, resistance, output, all within specs.

Greezeyrider, when I pulled the first VR off the bike I found possibly what you are describing. That was one of those "AHA" moments because the connection was corroded. I replaced the VR with a solid wire from the VR to the BAT.

Touchdown, I have tested the coil per the manual and it also passes.

Tom84FXST, I thought of that yesterday when I put on the new VR from Harley, I tested that wire with the ohmmeter and visually and it looks good.

All these replies make me feel like I am on the right track as these are the things I thought of initially. We need to dig a little deeper...

 

Well, if there's no AC voltage across the battery with the regulator plugged in, I dunno what's going on. Tach doesn't act weird when the bike is acting up, does it? You might just pull that wire all the way back to the regulator and inspect it that way, or even replace the wire by splicing a new one in at the regulator and running it up to the breaker.

I hate to throw parts at things, but otherwise I would guess either voltage regulator or ignition module.