This morning I decided to pull out my reed cage for a quick inspection. I pulled out the spark plug so I could turn the engine over and quickly peek at the piston too. I put the bike into fist gear and slowly spun the rear tire. What I noticed was a loud, hollow knocking noise at TDC and BDC. I know the engine noise is normal for a KDX. My friends bikes are no louder or quieter than mine. Has anybody else noticed this with their bike? It almost seems like a problem with clearance or a wrist pin. My local dealer say's that replacing the piston with one other than OEM, makes it considerably louder. Has anyone had any luck reducing this noise? Has anyone installed a bige bore kit and have the same noise?