Did you do this work yourself????????Hey everybody....I'm having some issues with my evo engine. Put a new top end on. When it runs I have a nasty hollow sounding knock coming from the cylinders. Pulled the plugs so I could turn it over with the back wheel. Sounds like when the pistons reach the top of the stroke and start back down there is a bit of a clunk clunk.the rest of the way through the stroke it sounds normal. Any ideas ?