My 2009 Electro Glide Ultra Classic had been in the shop for 6 mo. from an accident I had in Oct. 2014. I picked it up at the shop an was told that they had changed the oil out to Amsoil 20w50. Cranked it up cold and the oil pressure was around 34psi. The bike rode good. About 30 miles later I let up off the throttle and noticed that the oil pressure looked like it dropped to zero. It was a warm day and the heat from the motor was real high. I was afraid that I had a leak and lost oil. I checked the oil and it was still full. At 70 mph the oil pressure went up to about 15 psi. The idle pressure was about 6 psi. I took it back to the shop and they checked the pressure gauge and the new gauge checked the same as the old one. Another sending unit was put on and by this time the bike had cooled quite a bit, so when it was cranked the pressure read 32 psi at 2000 rpm and about 15psi at idle. 30 miles later the pressure dropped down to 15 at 70 mph and about 6 @ idle. Took bike to Harley shop to put mechanical gauge on. They had to wait for bike to cool some before they could hook up the gauge. Reading was 32 psi at 2000 psi. Paid to put a new sending unit on and when I left every thing was reading good. 30 miles later the psi dropped to 15 psi at 70 mph and about 6 psi @ idle. Every thing was still the same when bike got hot. I replaced the pressure relief spring with another and now the cold crank is about 55 psi, about 10 miles later the 2000rpm pressure is about 32 psi and the idle is about 15 psi. about 10 miles further the 2000 rpm pressure is about 16 psi and the 70 mph is about 24psi. New spring increased pressure by about 10 psi. Idle hot is still about 6 psi. Are these pressures safe to run? What can be opening up enough when the engine is hot to allow the pressure to drop?