I think I posted pics of the valves in my Brush Bandit 65 chipper with a Wisconsin VH4D. 3 of the exhaust valves were cracked. Put all new valves and new knives in it. Hit the key and purrs like a kitten. It actually growls. There is no clutch, it's direct drive so as soon as you turn the key, your turning the chipper disc too, so it makes a lot of non engine related noise. We are painting my daughters house. She bought the two acre lot and house two doors down from us. As soon as I get the chance I've got to put all the safety shields and engine pans back on. We suspect over heating, or a lean condition, to the cracked valves. Carb seems to be tuned right. I made sure all of the fins on the heads are clean. The manual says the engine pans are a major part of cooling. I thought the thing chipped really well for a small chipper, when it was running on 2 cylinders. Now Ican't wait to see what it does with a happy engine and new knives.