Recently bought a sportsman 500 ho efi. has 145 hours,and there is some sort of rattling noise comining from the engine,seems to be on the right hand side,i can here it from cold start at idle and seems to get louder at higher revs espeacially riding if I hammer on it and a lot of people say that these bikes all have that noise and its normal howerever I really just want to know what it is! I changed all the fluids and spark plug. checked valve clearance and even took the bindex off and cranked with the pull rope to make sure it wasn't from the bindex.There is nothing that I can find that is loose. Any ideas?