Pressurising the rocker cover!!

[mowerman]

On the RBRR I noticed oil leaking from the rocker cover filler cap! I have bypassed the conventional breather arrangement (because of K&N filters) into a vented catch tank on the bulkhead. There is very little oil in the tank but lots over the engine  :-/ Has anyone else had this type of problem with a modified breather arrangement? The engine is mildly tuned and runs on 10w60 full synthetic oil. Do any of you racer types with tuned engines suffer with the same problem? I have checked the hoses on the breather and there are no blockages  :-/ I also find it strange that it hasn`t blown the cork gasket ?Any hints or tips on how to overcome this issue gratefully received as the oil costs £15 per litre!!! Thanks, Steve.

[Nick Jones]

Is the breather actually clear?  Can you blow through it?

Nick

[bodders1]

Can the catch tank vent easily to the outside air?  If the vent filter on the catch tank is blocked or restricted, the system will pressurise, and the vapour will find a way out at the weakest seal in the chain.

[Jonny-Jimbo]

Is the oil a touch thin? Too thin and it'll piss out of any gap it can...

[JohnD]

mowerman,
The Silverbcak engine does the same -I thinkits the cap.
With the engine hot, take off the filler cap and rev it.
If there is a mighty rushing wind out of the filler aperture, you have excess blowby.
If only a slight breeze, or pulsing flow, you haven't.
The above points about blocked catch tank vents still apply, as any engine gets some blow by.
John