pulled power valve on my sons 2002 ktm 250 sx and cleaned. It was stuck so had lots of carbon build up. when we put back in bike everything works smooth until you put roller in right side then it wants to bind up. I can see the roller shifting in the hole in cylinder head. Can these wear down? If I coat with grease it moves somewhat freely but I know the grease will not stay there once it gets hot. Looks like there is two much clearance.