Hitachi ex300lc-3 clicking in engine top end

Ok so i have a hitachi ex300lc-3 and the engine was rebuilt about 500 hours ago it has developed a engine tick in cylinder 5. Can smell a bit of unburnt diesel but no smoke in exhaust black or blue only when start for 30 seconds. I backed the line off at each injector to see if it was an injector when i did number 5 the tick had disappered. I then switch the injector with on that did not make a difference and ended up with same results. I'm curious if anyone has ever had an issue like this with diesel engines where u back fuel nut off injector and the tick dis appears. The tick also adjust in with rpm up or down machine show no power loss and runs the same it does have some blow buy but I'm not sure if thats from the engine being freshly rebuilt not to long ago

Hitachi ex300lc-3 clicking in engine top end