Oil pressure problems

I had to split my engine cases because of the main output shaft bearing collapsing. I did the following to the engine -
1. I split the bottom half from the top engine case leaving the barrel and head intact.
2. Replaced the gearbox bearings.
3. Replaced the oil pump (some scratches from bearing pieces floating in oil)for a spare good condition Z900 pump.
4. New gaskets and oil filter fitted (sump O'ring) and everything carefully??? (obviously something went wrong) assembled.
All looked well but when the engine was revved out the oil light came on and would not come back off till the oil was cooler in other words after 3 to 4hrs of standing. Checked the engine oil gallery plug - no oil.
The engine has a baffle plate in the sump and has never given me problems previously under the same conditions.

I assumed that the cause might've been that I somehow forgot to fit the O'ring that goes above the oil pump and sits between the engine cases so I pressure tested the gallery with air and all appeared ok (blocked the oil outlet at the oil cooler). The oil pump O'ring is definitely there / new.
The second suspect was the oil pump and I now have a new oil pump from a GPZ1100 82 fitted I had lying about. Still the same problem.
I fitted an oil pressure gauge and at idle cold = 3psi and this can go to 12psi at around 6,000rpm. When the oil gets hot at idle = nearly 0 to 1 psi (oil light is off) and at 3,000rpm cruising = 3psi to around 6psi at 6,000rpm.
All appears ok till I take the bike to around 9,500rpm hot (power goes to 10,500rpm) pressure drops and the oil light comes on.
The only thing I can think of is that even though the O'ring between the cases does appear to be there, it might not be and the engine pressure exceeds the oil pump output but apart from that I've run out of ideas.

Added - I am using the same oil as I used previously - Castrol GPS semi synth M/C oil.

Bozo.
Just to be clear . At 9500 rpm HOT No oil pressure per your pressure gauge ?? And the oil lite then comes on as well ??

Correct, at around 9,500 rpm Hot, the oil pressure drops (on gauge) and then the oil light comes ON. If I rev it further to 10,500rpm the only way I can get the oil to pick up is when the oil cools (thicker). I have been thinking about this more and my feeling is that the engine cases when hot create a gap (maybe where the cases join) causing the pressure to drop.
I was hoping someone out there had a similar problem to back my theory before I start ripping the bottom engine casing off to check if the joiner hole O'ring has not escaped for some reason.

Last thought before tear down. You mention a oil cooler. Does it have a thermostat that might cause a blockage ? Just grasping at straws

Dave

Good suggestion but apart from the fact that its the same cooler as used previously it is one from a GPZ1100 '82, I'm certain they don't have a thermo, also just in case I primed it beforehand to ensure there were no air pockets (just in case)
I really appreciate your input Dave, your questions make me think about what I might've missed.
John

Im always here to try and help a friend John
. I hate to see you tear it apart again but looks like you need to. My advise is ASSUME NOTHING IS RIGHT, CHECK EVERYTHING. . Even the gauge and oil pressure sensors. Reclean everything, If pan has a gate make sure it swings free and has a little play for heat expansion. Is pump cavitation due to wear, speed, oil level, viscosity????? Missing gasket, O ring, gasket sealer buildup or pressure pushing silicon into a passage , Trash in oil pump screen , bad oil bypass valve, partially plugged filter

Just a list of thoughts since you don't want to miss anything
Good Hunting Bro
Dave

I had problem last year with my oil pressure. I have a oil pressure gauge installed on the crank case and all was fine and then my gauge pressure went wacky. The cause was an intermintent blockage at the galley gauge location (was really hard to diagnose) and the culprit was a small piece of old base gasket (stock graphite type) that was stuck in that area moving in and out or back and forth. At higher rpm the piece of gasket kept blocking the galley on that side of the block with increased oil pressure. I thankfully did not do any top end damage.

Your sure your oil pump is good? I would check and make sure that oil ring is the correct one also.

Doug.

WHAT was the bikes oil pressure prior to changes? These bikes use a high-flow, LOW PSI oil system - my own stock, low mileage KZ1100 will show about 6 PSI cold idle on 15/40 DELO 400 lube, dropping to about 1 PSI when hot. Factory spec is about 3 PSI at 3K RPM when fully warmed up as I recall. Variations in gauges, and using low viscosity lubes can vary readings a great deal...

Dave, Doug & Barry, you guys are champions thankyou, Doug you gave me one point I didn't think about. We all like to think we assemble motors clean BUT.... I will double check this before stripping the motor, have to admit Dave after outlining all the points it really looks like a strip down.
Why - because the only place I could have a blockage has been checked and blown out with air. I fitted an air nozzle to the hole where the oil filter bolt goes (after removing the sump) blocked off varies points to see if air leaks especially where the engine cases join (which is what I suspect when hot).
The oil I use is 10-40W semi Synth and I've been using it for years with no issues.
Gary, the pressures you outlined are exactly what I was hoping for. They seem to be on par with mine i.e hot idle 0-1psi, 3,000rpm=3psi to 6psi at 6,000rpm+ Your 6psi on idle cold would be due to 15-40 oil, mine is 3psi cold idle and can go to 12psi at 6,000rpm+
The oil pump has been changed for different type twice, I now have a new GPZ1100 pump.
I even checked the oil filter O'ring as some gaskets on the sump are thick which might create a gap. ( I bought a cheap set of gaskets which turned out to be twice as thick - what a waste of money).
The only other item I could suspect is the oil pressure relief valve in the oil filter block, I did push it up/ down from under the bike with the sump off and appears to be ok.
At this stage I'm gearing up from an engine removal and hope it doesn't end up being something other than a missing O'ring ??? or leaking. If this turns out to be the case it would be the first time I have ever made a stupid mistake like this (I have assembled at least 40 motors in my life time). I'll keep you posted when I get the balls to do this.
I have checked the sump gate, it appears to be ok and loose so it shouldn't bind when hot but again I'll recheck.

I eventually pulled the motor out after not solving the oil surge problem. DO NOT BUY CRAPPY GASKET KITS, I did turn out to be the oil gallery oil ring, I split the cases and changed the O'ring for a genuine. Now I can rev to 10K with no problems - NICE.
Thankyou to all that helped me.

Im glad you found the problem Bozo !!! :woohoo:

I only use stock or Cometic Gaskets.

Now get out and ride that Beast !!! :evil:

Dave

I have noticed over the years the gasket quality of aftermarket gaskets has gone down a lot. I rebuilt my GPz1100 engine with a Cometic gasket kit and had the following leaks.
Alternator cover
Clutch cover
valve cover
Cylinder base.
I replaced the base gasket with OEM, that stopped the leak but I replaced the others with another set of "quality" Cometic aftermarket gaskets. They all leaked again, All the surfaces were very clean and smooth. I couldn't afford to replace with OEM gaskets so I used a very thing film of yamabond on all the leaking gasket, both sides. That stopped the leaks very frustrating.