3RD Fin oil leak

Hello All
Well. Got sick of oily boots /clothes/bike etc etc so decided to investigate oil leak from front of head, 3rd fin up. 850 Mk11A with RH10 head. Read ALL the posts I think but couldn't come to a conclusive reason. Bit the bullet and pulled the engine out, removed the head but no obvious leak from the head gasket or 5/16 bolts near the pushrod tube. Decided to pressure test the head, so made a rubber gasket, popped the head back on and pressurised the head via the rocker supply line to 10psi. Sprayed the offending area with soapy water and located the leaks. Fine cracks bubbling to the side and behind the front 5/16 holddown nuts. Oil must be migrating from pushrod tubes but cant see any evidence inside the tubes. Not sure what the black marks are int he pushrod tube but certainly not crack there. Any suggestions to repair? I can only think of a thin smear of Devcon in the pushrod tubes in the local vicinity. I'm quite calm at the moment but it won't take much to look at buying a JAP??? bike HAHA. Any suggestions would be appreciated for repair/s. Anybody have a spare RH10 head for sale?
Thanks for listening
Steve
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You're in luck! Your new head is being cast in Adelaide at the moment.

There was a spate of porous heads back when these bikes were being made and the factory sent them out for treatment, my MK2A had the silver paint but that is long gone as I had it vapour blasted 25 years ago and no leaks since, so not sure if the paint alone will act as a sealant or maybe my head never had any leaks. You could try Glyptal paint on the inside of the pushrod tunnels

Some discussion in this thread.

porous-timing-cover-t26933.html

Did read this post:

oil-leak-the-head-t26204-45.html#p348258

Have you fitted a breather valve of any kind (Comnoz, Mikes XS etc.) It may help.


cheers,

cliffa.

Hi All

Thankyou for replies. Obviously I had missed some of those posts and have reviewed them. The bubbles come out along a fine crack so I am discounting porosity but not sure the welding will be successful. I think I will try a combination of repairs suggested, even if it reduces the leak I think I will be satisfied. I will try a improved breather setup as every little bit will help. She only gets used for 160km runs once a month. The rest of the time I just admire her simple beauty!
FULLAUTO - I wasn't aware your heads were being cast in Adelaide. Thankyou for supporting our local SA industry, heaven knows we need it!!!! As much as your head would be an obvious repair there are others out there more deserving of your efforts. If I put one of your masterpieces on I would have to tart up the rest of the old girl!
Thanks again.