'79 kz750b oil filter

Is there a filter with anti drain back check valve for this model?

No. The filter assembly has a "pop off" valve which is a spring and steel ball to allow bypass under excess pressure when the filter is plugged up.

As I've seen, the filter stays full of oil when parked because it is mounted horizontally.

Thanks, BH. That's what I thought. Mine apparently has a problem, because, all the oil is draining to the pan. When starting cold after a day or two, there is a squeal lasting a couple of seconds until the oil pumps up. Oil lamp stays on for a few seconds sometimes, as you recall from one of my other posts.

Using 10w40 Castrol motorcycle oil, no additives.

IMO, it's not the filter or the pump. The oil drains down from the bottom end of the engine and it takes a few seconds to pump the pressure back up to the engine. Mine also will have the oil light on for a few seconds sometimes at startup after sitting a few days.

If you have a factory manual, it shows the oil flow path. Coming off the pump it goes straight to the main bearings and rod bearings. The other oil "feed paths" on the output of the pump have orifices to keep the pressure up. The main bearing wear would directly lower oil pressure. I think the light staying on shows the pump has to really work to get the oil up into the bearings.

I am not sure what the squeal is at startup, sounds like a bearing. Mine used to have a "metallic" clickey sound until the light went out but no really bad noises.