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So I'm guessing that you set up your torque wrench and thought "maybe I should just try and tighten the nut first so I can see if the nut is not up to the proper torque" right? Not a bad idea but first you must consider the fact that as I mentioned before, standard torquing usually requires a small amount of lubricant under the face of the nut and also on the threads of the stud. If you did what I suspect you did and found the nut up to torque, then you've just experienced what I was trying to describe when torquing up a nut when the threads and the face of the nut is dry. As you torque up the nut, you start to drive out the oil from under the face of the nut and squeeze the oil out of the threads and at some point down the road the contact surfaces are too dry.

The only way you could check the torque would be to reference the nut to a fixed object (mark a line on the nut with a pencil or sharpie marker and extend the line to the head), then loosen off the nut and get the threads and face of the nut wetted with oil, then torque the nut back up to spec, then check your marking and see if the nut has rotated further than it was previously.

Yes of course Obvious now you point it out, I will do as you suggest and if the nuts don't turn any further than originally I will carry on with the new gasket, if they go a bit more put it back together and test

Just tried the first nut and it has turned around 4mm past the original mark so a promising result, I will do the rest in sequence and see how they go, could be my lucky day

It's 4:45 am. (in the morning ) here in Ontario Canada and I'm up thinking about this dilemma of yours. We have no history on your motorcycle so we need to consider all of the possibilities here of why you might have a failed head gasket (oil leak).

This may of happened because of a stuck oil pressure relief valve. The only parts of the lubricating system that would see high oil pressure and relieve to the oil sump or the atmosphere would be the cylinder base gasket or the head gasket. The oil pump by design is required to produce more oil than necessary to accommodate all of the required leakage through the bearing journals at all rpm's. The only way it can manage the various flows and create pressure is by having a oil pressure relief valve in the system. IF the motorcycle was stored with old oil in it which may have contained or likely contained moisture in the oil, then it's possible that the steel piston of the relief valve got stuck in the aluminium bore of the relief valve and caused a high oil pressure spike until the relief valve either popped and started working again, or relieved enough and got stuck partially relieved. Either way causes me to also include that one would be wise to check the oil pressure with a gauge and ensure the relief valve is functioning properly.

Oh the joys of working on old equipment. You really have to put your thinking cap on when trying to understand failures and come up with the remedies. Gaskets fail for any number of reasons and when you come across them, you really need to investigate the problem until you find the cause of the failure. Mating surfaces that aren't parallel, dries out gasket material which is not supple any more, incorrect torque on fasteners, incorrect operating temperatures, incorrect pressure across the faces of the gasket surfaces are just a few off the top of my head.

I think the main reason I initially pointed you in the direction of trying to retorque the head nuts is due to my previous experience with Volkswagen diesels. If you didn't follow their retorquing procedure every 50,000 km, then the head gasket would leak oil. The reason for the requirement was that the engine needed the head studs to be torqued up to almost the yield point of the stud and eventually the stud would yield causing the stretch on the stud to relax. One has to understand that steel has an elastic zone where you can pull it and release it and it returns to its before stretched state. This property of steel allows us to apply torque on the fastener and maintain tightness. When you over stretch a steel fastener, it will yield (or give in) and remain at the new length. In the case of the VW head studs, in order to maintain enough stretch on the studs to maintain the seal on the head gasket, the studs were torqued up to almost the yield point of the studs, then the cylinder pressure working on the surfaces of the cylinder and head surfaces would cause enough added stretch to yield the studs. In effect it was a engineering design defect which they chose to accept by requiring a retorquing of the head stud nuts. if you didn't retorque the nuts then you would have a total failure of the head gasket and have to replace it.

ARP have made a fortune in the head stud game for racers with modified engines. They recognize that when you build up a racing engine and add extensive cylinder pressure, that you can and usually do exceed the yield point on the stock head studs. They offer steel studs which have a higher chromium content and the tensile of the material is almost double what the stock studs are, but then you could pass the failure onto the threads in the cylinder block that the studs screw into. So it's critical that when installing their studs, that you follow their procedure which requires tapping the cylinder block holes deeper to accommodate the added stresses.

I guess for you, the bottom line would be to check the oil pressure and ensure that it's within the range as suggested by the service manual. For anyone else following this thread it's a bit of a lesson in understanding failures before attempting to correct. One must not forget to take in to account the fact that failures can be due to circumstances related to improper storage and long periods of inoperation. This last point I have to remind myself of when I work on my projects and sometimes I need to give myself a smack up the side of the head when I forget to take in to account all of the possibilities.

Thanks a million for your thought and explaination, I feel a bit guilty when someone like yourself spends more time on my problem than I probably have myself...but I can live with that I'm not certain of the bikes history but it has only done a few miles in the last ten years. I will try to get the oil pressure checked out precisely after retorquing the head, I'm thinking that maybe an untouched motorcycle engine can like all of us shrink a couple of millimeters over 33 years and 50,000 miles and a quick "nip up" may tighten things to useable again..Thats my theory until I run it up and it pisses oil out anyway , we shall soon see.

Just done the retorquing and every nut has moved a further quarter of a turn apart from the 2 in the tunnel on the starter motor side which stayed as before. I'm not sure how big a difference this equates to but suspect it could be enough to cause/cure an oil leak as in the VW diesels you mentioned.The engine only developed the leak a couple of weeks after I bought it last year after I gave it its first good run with the occasional fistfull of throttle so I may have caught it early enough. It would be interesting to know if mine is an exception or if all old engines with average milage loose torque on the head nuts. I'm short on time so won't have it ready for a test run for a week or two but will post the results as soon as I can.