'74 Mk II, Still Chasing Significant Cyl Head Oil Leak

Previously john_holmes wrote:

Best leave your email address off the post, there are spambots trawling forums looking for email addresses to add to spam lists.

On BSA A65's there are head studs they add O rings to, so it works on a similar engine, vitron is the best material for oil and heat resistance. Have you considered removed the studs and reinstalling with a sealant such as Loctite 515 or 518, this will stop oil migrating along the threads.

Also read this thread.

http://www.accessnorton.com/high-temp-head-gasket-sealer-comparison-t27001.html

Thank you John for your useful suggestion all around. Will edit my post and remove my email. Have thread sealant and will use. Also will pick up correct sized viton o-rings and put them in place.

I WILL stop the oil leak !

Ron

Previously alan_blackhurst wrote:

I had this problem last year. My fault hadn't emptied the breather bottle and the breather pipe was in the emulsified oil. I think that this caused the engine to pressurise. Which showed by leaking badly from the 3rd fin down. I have since fitted a non return valve in the breather pipe from the engine and make sure the breather bottle is emptied regularly. It hasn't leaked since.

Your problem maybe down to poor breathing.

Regards Alan

Good suggestion Alan, thank you.

I have a PCV valve (works as a one way check valve) on the line that comes from the transmission, right, side. I'll remove the PCV valve to assure minimal crankcase pressure.

Now the big "Duh" on my part. The oil tank breather near the fill cap is blocked off and always has been for the two years I owned the bike. That may be a huge part of why I have been unsuccessful in stopping the oil leak. I'll run a hose off the breather and hopefully solve my problem.

Thanks again for bring up the poor breathing possibility.

Ron

Previously richard_payne wrote:

Third fin up at the front is a favourite spot for oil to appear and the usual causes are either the inlet rocker cover gasket or the rocker spindle cover plates.

It seems odd that oil should run forwards on a moving vehicle but it does on the Commando and the third fin is where the hollow gallery between the rockers converges. Strangely, even on a clean engine it can be nigh-on impossible to see the oil migrating downwards but once it puddles up and runs forwards, it can seem like a lot.

There are after-market alternatives to the odd rocker spindle retainers but it is certainly worth dismantling, checking for flatness and refitting with new gaskets.