I have a 2012 Goldwing/Hannigan Trike. Every now and then when I try to use reverse, I get a grinding sound, like the gears are not meshing. I am guessing that I might need a new starter. The bike starts OK with no grinding sound. This only happens when I am in reverse and it doesn't happen every time. Can anyone advise me of what the problem is and what I need to do to fix it?