Still beleive that borrowing another starter is your best bet to see if a starter is your problem. Having a spare starter is a good think to have. Have you ever tried running a jumper wire from the battery to the starter terminal?
No experience with the vibration plate. Bought our engine used and it didn’t have one. Don’t recall ever seeing one being used and I don’t think we had any more starter problems than anyone else.
LAD Specialties customer / tony kart / rotax / kt100