New rider ,got 60 miles today,I'll tell you what,it is not that warm in Wi. yet.On my way back home after the bike was good and warm I noticed a noise that really got my attention,it sounded like metal on metal coming from the motor somewere,I did not lose any power and the bike rode and shifted ok.I have noticed this acouple of times before and the brother in law said,thats just a shovelhead ,they all make that noise when they get warmed up.Is this true or should I be concerned?If anybody is familiar with this,what is it ?Bike is 84 sportster and the motor is 100% stock thanx.