I have an oil feeding problem with my 1937 Model 9. When starting the bike the pressure gauge goes to the upper limit (fine) but when riding it drops to almost zero. Driving is therefore forbidden. All pipes are free as are the fittings. So I took the timing cover off and found that the pump gear rotates almost freely on its axis and is not fastened by the top nut which in turn is connected to the pump. Should it be fastened? And if yes, how? The outer cover doesn't go off.