Topic: Oil pump/sump

[beemerbum]

When I rebuilt my K2 750 motor, I replaced the oil pump with a freshly rebuilt one from CycleX. The bike runs fine. Oil pressure came up quickly on start-up. The light stays off as it should. However, all the oil migrates to the sump after a day of sitting. I would like to think the pump from a reputable outfit is not at fault. I'm told that the check valve keeping the oil in the tank should come to life after a few miles. I have only put on 20 since the initial startup. Is there any validity to that idea? BTW, the pump was fully primed before installation (no bubbles)

[PeWe]

If pump quickly can refill tank probably no problem.
My K6 was like that from the very beginning. Oil did not stay in tank over night. Just touching the dipstick 5-10mm.
I called a friend and worried about oil level and got the answer typical CB750, just start it have a ride and check again after 20 minutes. This worked well so I did not worry.
This was May 1979.  Bike had done 18.000 km in total.

Oil warning never showed up either, except for when engine was not running.

I replaced the pump after around 100.000 km (2015) The other pump restored with seal kit. I made sure the valve (piston) could move by ease.
Never a pressure issue with old so scavange must have pumped up oil from pan quick enough.

I have noticed with good pumps keeping oil in tank that oil can disappear really quick when parked on sidestand idling from cold. I saw oil pressure light and pressure was jumping from 0 to 20PSI on gauge, tank was empty.
After that never let bike warm up on sidestand.
This has happened on both my CB750s. I guess  the pump does not reach oil in pan when leaning too much.

First time on my K2 I initially thought had got too little oil by mistake. Gave it a liter I had to take out when warm filling the tank.