i drained the old gas and put fresh gas in it .it helped a little but noise is still there i am guessing it is cam chain , i checked the push rods and marked them when i put the new head on , rolled them across a flat surface , and checked for up and down play on the piston rod but i didnt go past the top end thinking that was all that was wrong with it , i rebuilt it for a friend , it had been sitting for a couple years with a seized piston