If it's a Predator ?
Had one of those for a couple of hrs. , & ended up taking it back to HF,, because the valves were to tight,, & the rocker arms were not centered at all over the valve stems ect.,, & couldn't get them to line up better.
It was pretty bad.
I would pull the V - cover & check that out.
Added,,
Did you completely remove the governor from inside the case ??
I