Mother has a RTV500 that she uses to get around the farm. Starter will not crank. Battery is fully charged. All cables are tight including those on the starter. Nothing happens with the key when you try and start it. It has been a good vehicle for her and has about 500 hrs on it. Kinda stumped on what else to check as everyone has said it is rare for a starter to go bad.... any help would be great so i can get my 70 yr old mother back in business!!