I have an 09 kx 250f and it starts fine cold but warm its a bitch, anyway I'm checking the valves for the first time and how much pressure do you use to get the feeler gauge btween the shim and lobe. I have to push pretty hard to get them in and it feels like I'm opening the valve by doing it. I'm very mechanically inclined and it I don't think you shouldn't need that kind of pressure. I would think light pressure in and out. nothing that flexes the feeler gauge, right? Shimming seams pretty simple but it looks like you need the proper reading to get it within spec.