excessive pressure in cam cover possibly causing leaks

[Brocky2]

Hello,
I have done a major rebuild of my CB550K3 1978. I finally have it running fairly well but I have oil leaking out of my cam end covers which I know is not unusual. I have replaced the rubber O rings on the cam end covers and the aluminium and copper washers on the cam end cover mounting bracket bolts but it still leaks from there somewhere. However, it also seems to be bubbling out of the bolts holding the large cam cover onto the cylinder head, the ones inside the rubber gasket.  The bubbling bolts are not the bolts holding the cam end cover in place. If you blow into the breather you can push air in but then it stops going in. Should you be able to keep blowing air through? It's really annoying as this is my last fix. Any suggestions or help greatly appreciated.

[McCabe-Thiele (Ted)]

On the positive side you know there is oil reaching the camshaft.
If you remove the vent pipe from the top vent cover can you feel any air venting out?

Update: Did you fit the oil restrictors & O rings on the block?

[K2-K6]

Put the breather into a glass jar of engine oil when running to see if it's sucking or blowing, that'll at least let you see if there's pressure or not.

[Johnny4428]

Also don’t want to state obvious but did you place the sealing washers underneath the end cover brackets?
(between brackets and cylinder head)

[Oddjob]

IIRC there are 6 bolts inside the oring gasket and 6 outside. The 6 inside are supposed to be fitted with sealing washers so they don't leak, in theory that is, never seen one leak myself. Best type of washer is alloy and then copper IMO.

As for the end cover leakage. Check the threads in the head where the bolt goes, I've seen more than a few blown out and then the bolt fails to pull hard enough into the head to crush the washers and thus seal the bolt hole. This is normally caused by testing for oil coming up after a rebuild, this then flows into the bolt hole as it's right next to the oil passage oil, the bolt is then inserted and it tries to compress the oil at the bottom of the hole and of course can't. The bottom threads then get blown out by the pressure and you find the bolt will tighten up and then spin when enough pressure is applied. Any oil getting down those holes should be sucked/blown out before the bolt is fitted or you risk this happening.

[Brocky2]

Thanks All for your input.
Yes I'll check the pressure coming out of the breather hole to get a feel for whether its pressurising. Good idea thank you also the ideas with the oil sucking or blowing. If it is pressurising what might cause that? I have replaced all the valve seals and have the valves recut and reground professionally.
The cam end cover bolt currently has two copper washers on it one above the bracket between bolt and bracket and one between the bracket and the head. I might try replacing the one between the bracket and head with an aluminium one. They both tighten down nicely although the leak only seems to be coming from the left side one.
I've tried various Viton (higher temp. spec than Nitrile) O rings in the cam end cover in an attempt not to pay the huge price for Honda ones but have given up and coughed up for ones from David Silver. I'll fit those in the next few days. Fingers crossed.
I have tried to use copper washers on the bolts holding the main cam cover down in order to seal them. It seems to be working so far. I just wasn't expecting to see these leak oil.
Thanks again for your ideas. 

[Brocky2]

Good question re oil restrictors. Yes I did fit them on the rebuild.

[K2-K6]

Virtually all of these (combustion engines in general) will generate pressure internally, primarily from leaking past the compression piston ring. More recently, cars and bikes have breathers connected to intake system to avoid expelled gases being vented to atmosphere, even pulling slight vacuum in crankcase volume while doing this.

It's usually small and contained within the volume of breather facility to avoid anything much building up to eventually become a problem. Obviously this relies on the breathers being clear to operate.

Copper washers, you can aneal/soften them (they gradually work harden through using) by heating to red colour, then quenching in cold water. This will make then as soft as possible to work well in sealing the joints they've been used on, at the same tightening torque setting.

[Oddjob]

Viton or Nitrile orings will make no difference so long as they are the correct size. Meant to be aluminium washers below the bracket as they compress and seal quicker and easier than copper. It's the distortion which seals the opening.

The restrictors are fitted to increase the pressure of the oil around the crank bearings, not specifically to reduce it in the camcover.

I'm wondering if the oil pump is over pressuring the system, it does have a relief valve fitted to stop that but I've taken a couple apart recently where the relief valve was frozen in place, maybe think about checking that as well. It's the 14mm headed cover fitted on the lower right of the pump, take it off and there is a spring and plunger underneath, the plunger should move freely up and down it's tunnel without the spring fitted, 2 of mine were stuck solid.

Also check the breather pipe isn't pinched anywhere thus blocking the breathing system.

[Brocky2]

Thank you K2-K6 and Odd Job,
Right thanks I'll replace those copper ones below the bracket with aluminium.
I'll also check the pressure relief valve on the oil pump. Can I do this without draining the oil?
Are there any disintegrating O rings I need if I check the relief valve?

Thanks again for all your suggestions.

[Oddjob]

If the oring leaks I have some spares.

You can probably do the job with minimal oil loss. Stand the bike upright, even better if you can lean it away to the right, maybe a small lock of wood under the left hand leg of the main stand.