I'm doing a top end on a 98 kx500 and the exhaust valves are so gummed up i cant remove them. I've spray a whole can of carb cleaner on the prts i can access thru the exhaust port and bottom of the cylinder. I heard of using oven cleaner but it say not to use on aluminum on the label. Im on the verge of using a slide hammer... what does anyone think of hosing it down w/ pb blaster? I've already tried wd-40, fluid flim, BR 6 in 1, and some gentle heat. Oh ya another option I 'm kind of nervous to try is submerging the whole cylinder in that carb gunk remover stuff, majorlly caustic stuff! The valves are stuck closed and the action shaft(top end one) is moving freely. surfs up! BT