A few month back I replaced my dizzy for a rebuilt one and ever since it has had a slight top end tap that rises with revs and a slight misfiring, also the last two days it has been really tappety on cold start for a few seconds.

Is there any way to check followers by just removing rocker cover?
What exactly am I looking for?
And can anyone recommend where to buy a replacement kit of good quality, I don't want to upgrade it as im on a tight budget just an oem one will do

Thanks