rincon snapping noise at rocker cover

2005 rincon 650 has a snapping noise after I installed the rocker cover. seems to do it when the valves close ( pushrod going down). went into it to install new camshaft, timing chain, guides etc. Only turning it over slowly with pull rope to be sure rocker followers are engaging with pushrods. never noticed noise before and not sure if it is ok or not. Have removed rocker cover several times to be sure rockers/rods are meshing. any advice appreciated.