Hi John, After getting lines correct again, & starting again how long did you wait for return?
70 seconds is an eternity it seems.
As was stated pressure & return are 2 different not connected systems. The only shared item is the driving block.
With no load rod bearings will last long time at 7-10#.
Hooking test gauge will tell feed pressure, but will tell nothing about return side of pump. Yes feed & return share same casting but feed & return are stand alone systems.
I’ve never once seen pumping air turn light out. So you have some feed oil at least.
A few thoughts before removing pump. Did you wait the full 70 seconds the last test after correctly hooking up hoses?
If feed side is working but return not, oil level in tank will drop. Rather quickly. You can obviously see this with flashlight with motor running. Don’t let tank run dry!!
Now drain motor sump into container. Measure how much comes out. ‘70 has short scavenge tube. Expect 90-120cc if all is well. No return working what went low in tank will be in motor. That is a real deal test. Quart low in tank that quart plus the normal amount will drain from sump.
One bike had leaky check ball on return. A mile or two full tank was half down. That oil was in bottom of motor. There was still a return stream at tank, but no spurts of air as you should see.
Bench testing pump failed on return side check valve test. Inspected showed ball seat out of round. New pump cured.
Did you bench test pump per shop manual
? That test is very real & valid. A good pump will have zero oil drop at port in 15 seconds. Any drop at all is a fail.
If dirt, gasket chip etc got into pump after start up that can happen, but you know if passed bench test pump was good.
Cleaning pump should make it good again. Silicone sealant if flaking of is weird. It will deform & suck through screen then get stuck in ball valve or PRV.
Did tank level drop unexpectedly?
I made video of testing oil pump. Pm me your email if you want a copy.
In a side note, the threads got pip pressure switch is 1/8-27 NPS. That is straight pipe thread NOT TAPERED NPT.
The adapter fitting for pressure is not made or readily available. Trust me don’t bother looking.
I have Harbor Freight automotive oil pressure test kit. It has gauge, long hose & a bunch of fittings. Use either the British straight pipe adapter with small oRing from ace hardware or 1/8-27 taper. Pay close attention now. Finger tight on this fitting only!!!! Tight as you can with thumb & finger. Any tighter you risk grave damage to timing cover!!!
Of course it will drip oil. No matter. If pump is making pressure the gauge will jump right up. I’ve done this on straight thread cover a few times. I made proper adapter in my lathe. Most don’t have one.
So first off did tank drop? How much oil is in sump?
I’m familiar with spin on filters dry frame 650. If you don’t pre fill filter with oil, add an additional 30-40 seconds to the return time. It’s really scary to wait nearly 2 minutes. But remember the feed pump is all important.
If you’re worried about rocker oil, pump oil into skinny rubber hose with pumper oil can. Rockers need very little oil.
If you remove pump don’t just take it apart. Bench test first.