I'm working on a 2013 Roadglide. It's running big bore jugs and Redshift cams and has been running well for a long time. It started to make some big "ticking" noises like a tappet had collapsed. When it came apart the front exhaust tappet was pretty dry. The plate and pump easily passed a bench inspection. The tappets were replaced and back together it went. Still a noise! So it came apart again. The front pushrods were kinda dry but the back ones were full. This bike shows 30/35 psi when running. The tappets are stock. My question is; what would limit the oil supply to the front tappets/pushrods but not the rear? Any ideas?