Hmm. Well mine started making the noise the first night I went out with it and got it on the highway. It was sitting for about 3 months cuz I needed to change out the head gaskets. It eventually went away on its own though so i'm not really sure why yours would crap out like that and weird how it comes and goes. Maybe an oil change might fix it for ya. Every once in a while when I change my oil, I use that motor flush that they sell at autozone to clean out any gunk it might have. You pour the bottle into the motor, let it run for 5 minutes and then drain and change the oil.