15FLHTK Found on it's side after hrs. Seemed OK, no issues found. Bike was ran 200mi before valve knock. Immediate oil check found 2.5qt low refilled, 50mi home all good, no engine noise. Oil check at home and had high pressure air vent from dipstick. Oil change with same result. Pressure eases after engine off for little while. Never heard/seen this. Oil in crank not scavenged? Or breathers? Best test with limited tool access (long way from home)