I have a 98 Fatboy (EVO Engine) with 25K miles on it. The oil pressure is very erratic and not consistent. I've already changed the oil and filter and checked the oil level. I also replaced the relief valve spring. I even took the valve out to verify it wasn't sticking. The oil system is stock and it has a Harley filter and Harley 20-50w oil. I also checked and cleaned the tappet screen. Oil pressure can be 40 at start up, 30, 10 or zero. Sometimes it will increase when I rev the engine other times nothing. I have both an idiot light and a gauge. I expect to see a decrease when the bike gets up to temperature and at idle but this makes no sense as the oil pressure is all over the place. I changed the oil pressure sending unit and added the gauge just above the tappet screen. I also removed the the sending unit when it started I had pressure and oil was pumping out of the hole. Also did this when the gauge was reading zero and the oil light was on and no oil was pumping out of the sending unit hole. Basically this is a real problem and intermittent. Has anyone ever had this problem? Thanks and ride safe.