Commando cylinder head again

Check out the link provided by Robin Goddard's reply to previous cylinder head post. Very informative and exhaustive.

Previously wrote:

I remember reading, but can't remember where, that you can fit a 750 commando head on an 850 commando engine after a simple mod. This is supposed to cure the leaks caused by porosity, apparently common on the 850 head. Can anyone comment? Has anyone done it? How?

Michel.

If your cylinder head or any casting suffers from porosity then get it resin impregnated, you could try try 01613441004, can't remember the company's name, and I haven't used them either but I do remember getting the ad out of one of the classic mags. Resin impregnation is definitely better, and should be cheaper, than arsing about with cylinder head swaps/dubious mods,

Simon.

My 850 had the leak from the third fin up at the front. It is not porosity, and resin impregnation will not help one little bit.

The cause is a very fine crack through to the pushrod tubes.

It is a case of putting up with an oily bike, or change the head, although finding a good 850 one is very hard.