Topic: Oil delivery problem after CB550 engine rebuild

[bryanj]

Only way crank bearings would have any effect is if clearance was way too large,
Oil light out says pump is getting over 7psi is all, might be worth temporarily plumbing in a gauge to see what actual pressure is.
Did you strip and check pump? Too big a cover O ring drops pressure as will a sticky relief valve.
If you have an air line i would be tempted to remove the pressure switch and feed air in with filter on and see if plenty of air is comming out where restrictor jets go

[Nik-bot]

Thanks for the advice.

Today I checked the pressure relief valve and it was not stuck (slid out easily after some light encouragement). I had checked the oil pump when removing it from the previous engine and it was in spec...

I can't check actual pressure at the moment since I have removed the cylinder head.

Next time I get time, I will pump air through the pressure switch orifice to check flow to the head and I guess pull the pump to re-check everything.

For what it's worth many of these engine parts are from a past life where the engine failed leading to oil starvation and a spun rod bearing, the oil pump assembly is one of them. I thought I had diagnosed that previous cause when finding that the oil filter had been installed askew, partially blocking the intake.

[dave500]

i wonder if the oil tunnel has been rubbed through by the primary chain in the past?this one came close!

[bryanj]

Thats a possibility but the 550 was recast from the 500 and does seem to have more clearance, still possible with knackered chain though

[Nik-bot]

Nice outside-the-box thinking!

I was able to find a disassembly pic of this area and there is no damage

[dave500]

cool,press on.

[Roscoe500four]

Hi. Don't know if it helps but once when I rebuilt my 500 Four, I put the pressure relief valve in the oil pump backwards and was having the oil pressure light coming on when I'd pull up at lights. Did an oil pressure test and it was dropping right off at idle. Relized my mistake, swapped it around and all good since.
Hope this helps.

[Nik-bot]

Today is a US holiday so got to continue this project...

Recap: new engine build has low oil pressure on top end. Verified oil passages from case thru head to cam journals are all clear, including restrictor valves. Checked for free operation of the oil pump pressure relief valve

Today I removed the oil pressure sensor and blew compressed air into the orifice. A couple of burbles and burps later, oil flowed up to the area where the restrictor valves fit into the head.

Reviewed earlier comments and someone said to ensure the vacuum hose attached to the filter screen is stiff enough. I drained the oil and did this and it's very hard (I reused this hose from prior engine). Can someone explain to me the function of this vacuum in the oil delivery? Picture: https://photos.app.goo.gl/D7jwsnMUKLKTBXk98

I guess my next step will be to re-check all specs on the oil pump. Someone also said to check the o-ring on the pump housing is not too large - I'll search for info on how to determine this.

Beyond that I'm struggling to think of what else I can check...

[bryanj]

IT IS NOT A VACUUM LINE its the suction pipe for the transmission oil pump on end of primary shaft

[Nik-bot]

Thanks Bryan. I'll move on to the oil pump. Any additional guidance will be appreciated...

[denward17]

If that suction pipe is hard/old, could it be leaking not allowing enough suction?

[bryanj]

But that would only afect the gearbox as the whole of that big filter is submerged in oil

[bryanj]

Two possible thoughts

1 there is an air leak on suction side, have you rebuilt the pump with a thicker O ring under the cover, should be 46x2

2 primary chain has worn through main oil gallery and pressure is just returning to sump, mor likely on 500 as 550 casing was recast but possible if chain really bad

[Nik-bot]

Under the oil pump cover I found two o-rings, stacked. Together they measured 2.24.  Looks like this could be the culprit?

[bryanj]

Probably, with a thicker O ring  oil will escape the pump at end clearance

[MauiK3]

Wow, two o rings, pretty bad solution. This may be it