Low oil pressure, check the pump and relief?

I just finished measuring the oil pressure on my KZ650. The oil light has been coming on after about 30 minutes of riding.
I have new 15W40 Rotella (JASO-MA) oil, and a new oil filter. I found that I'm missing the flat washer from the oil filter assembly.

At cold idle I get about 8 psi of oil pressure. After 10 min of idling it drops to 4 psi.
At which point my 4k rpm psi is at most 15 psi. Should be 28-36, right?

I've attached a pic of two plugs the other two look very similar. These were cleaned 25 mi ago (4, 15 min trips)
A bit of oil on them? Also, I notice the exhaust for 1-2 has a very definitive pop-pop sound, Exhaust 3-4 sounds muffled.

Here's a link to a video of my KZ idling. Does the engine sound ok? There's some mechanical noise, but I don't know what's normal.


I think my next step may be to drop the pan? Bearings, relief valve, oil pump/oil pump screen?

The pumps rarely fail but the screen could be gunked up. Definitely drop the pan and look. That pressure looks dangerously low if the readings are correct. I didn't hear anything noteworthy on the video.

I have so little experience with the KZ650, I hesitate to give much advice....
I would do all the easy stuff first too, as in new oil filter with proper washers and compression spring assembly, maybe dropping the bottom pan, clean out the oil pump pickup tube and screen. Heck maybe even drop the oil pump out at that point if possible. It's easy in the 900s and KZ1000...

Pressure bypass-relief valve: be cautious with unrealistic expectation there... the whole idea of the bypass valve is to shunt oil around a clogged oil filter, which is causing excess oil pressure... not really to set over all oil pressure.
That rather implies to me that the max pressure is already set before getting to the bypass valve.

But, as mentioned, oil pumps are really robust.
Once out of the engine, you'll see how stupid simple they are.
However, I'd be thinking about babbit wear in the plain bearings myself too.
Keep in mind that all the plain bearings are in actually in parallel with the source of "oil pressure", and dumped into the bottom of the engine when returning to the start of this cycle....so all it takes for the pressure to be low is one or two bad or really worn out plain bearings.

Drop the pan and inspect the oil pump and strainer. If the oil pump has scoring in it, depending where is is, it can be smoothed out. In your manual it explains how to check the clearance between the gears (with a feeler gauge) and what to do about scoring.
Steve

Ok. Cool. I will drop the exhaust and pan tonight and have a look.
I'm really hoping it's something simple like a clogged screen. I've seen pictures of some pretty bad ones.
And I'd certainly be ok with a bad oil pump, as they're pretty cheap on eBay.

I took three and made one. For the Z1/KZ there's a thinner gasket to bump up the oil pressure.
Steve

The 650's run higher oil pressure than the big bikes. The pressure relief is actually pretty important. Replace the spring and ball. Clean out the oil pan and check the pickup screen. I would doubt the problem is in the pump.

Tyler wrote: The 650's run higher oil pressure than the big bikes. The pressure relief is actually pretty important. Replace the spring and ball. Clean out the oil pan and check the pickup screen. I would doubt the problem is in the pump.

And, keep in mind that there is a difference between a "pressure relief" valve and a "pressure bypass" valve....
A stuck oil "pressure relief" valve dumps pressurized oil right back into the case pan/bottom.
So, if possible, you would definitely want to pull the relief valve apart and see if it is stuck or plugged with something.

I dropped the pan and......it's very clean. Some gunk and some bits of carbon, but it and the oil pump screen is very clean.

But, I think I'm missing one of the three o-rings! One stayed on the pan, one is in the block next to the oil pump, but the one at the rear near the oil filter is missing! Please tell me this explains my oil pressure problems. ::fingers crossed::

The oil pressure relief valve looks fine. No scratching, The ball looks fine and the spring measures 20.5mm.
I don't think the FSM gives a service limit for that spring though.

When replacing oil pan gaskets I generally leave the block side dry or perhaps use a bit of dressing, and on the pan side I use black permatex. Do y'all share the same technique?

I think the O'rings are there for a reason... I hope you found the issue.

I hope so too. I searched the forum for someone with the same problem but couldn't find anything similar.
DPO strikes again!

That would do it if your sure it didn't drop out too........ looks like a after market gasket so its been off ..... be sure the 90mm o ring is in the filter groove too. I swear someone on here forgot one and burnt up his top end but forget where it was. Not sure on the gasket I left mine dry nos Kawasaki .