Had that happen once a couple of years ago when my starter bolts came loose from the inner primary, luckily I gave the solenoid a few whacks with my leathermans and it did disengage, - good thing it did, but my 80 FXEF also has kick start, no problem getting home and fix the problem. I do have a battery disconnect switch for my ground wire and will get around to installing it asap but also like the extra solenoid Idea, learn something new every day.

 

If the timing is off where the piston wants to fire backwards --the contacts in the solenoid will weld togeather