I put over 300 miles on my '86 FXRS over the weekend, and stopped to fill it up before heading home yesterday.

When I hit the starter button, the starter motor was running, but it wasn't engaged to the flywheel. When I let off of the starter switch, it kept going. I turned off the key. It kept going. I turned off the switch on the handle bars (right next to the starter switch). It kept going. I tried beating on the starter solenoid. It kept going. I finally remembered I had a Leatherman tool in my pocket, so I disconnected the battery, but the starter probably ran for almost two minutes while this was all going on.

I hauled it home, and it works fine this morning. I still ordered a new solenoid (likely culprit?) and starter relay (they're cheap) from J&P as I don't want this happening again.

Anyone ever had such excitement?

 

I think the solenoid is the most likely culprit. Since the starter was running freely with no load, I don't think you would have caused it any damage.

 

I had that happen to me outside the pub on my old 84 Shovel years ago...like you we disconnected the battery and then reconnected it. I push started it and rode home....pushed the start button and all was good...never happened again.

 

Happened to me once after I washed the Sporty. I think I got water into the switch contacts in the starter button which caused the switch to short, energizing the starter. I started riding, then heard the starter motor start cranking. I worked the switch back and forth, and the starter finally quit.

 

My issue was low-voltage starts over time pitting and corroding the starter solenoid electrodes. That pitting made it worse until the starter motor would just spin like you said and I'd jump out the power shorting to the frame with a screwdriver. Once I pulled the cap off the solenoid and replaced the electrodes (that's oversimplification on a 1990 Softail), I never had the problem again.

 

I think a lot of us have seen this at least once.
Suggest you will solve the problem with the new solenoid and relay but would advise that you service that 28 year old starter while your in there .
Also clean out the bar switches with a good shot of WD40 or whatever you choose . See previous posts regarding this procedure.

 

If the problem was a faulty (stuck) relay , the solenoid would be energized and the starter would crank the engine (not spin freely).

I think the issue is inside the starter solenoid, I bet the contact disc is broken loose from the shaft, causing inadvertent electrical contact.

This would cause the starter motor to be energized, (the solenoid coil would not get power unless the start button was pressed), spinning but not engaging the ring gear on the clutch.