This may be an old thread but I swear to the big guy this just happened to me today, 5/21/20. I just came in to search and thanks to ChimneySweep I didn't have to look to far...so far anyway. I'm hoping its my battery which is charging as we speak. Lights come on but basically sounds like my lawn tractor when the battery doesn't have enough juice, wants to turn, but doesn't. I've had the bike for 3 1/2 - 4 years now and still have the battery that came with it. Not sure how old it was when I got it. Hey, with a lot of 20+ year old bikes out there, this stuff never gets old!