Thanks Bert, "easy bit" might be overstating my understanding. Be that as it may, I have some questions that may indicate how deep my ignorance is;
I assume, and correct me if I am wrong, that a failing head gasket and/or a failing valve guide would, to some extent, affect the performance from the cylinder that had one or both of those conditions. If one were fortunate enough to have BOTH of those conditions occur in the SAME cylinder (rather than one condition in each cylinder), then would pulling the plug wire on one cylinder at a time (and running the engine) give one a reasonably good clue as to which cylinder was so affected? That is, pulling the plug wire on the cylinder that is NOT affected would allow the engine to run "better" than pulling the plug wire on the good side.
Would the so called "compression run off test" reliably confirm which side is fouling things up?
If the valve guide or head gasket has failed on the side that "powers" the fuel pump, would the fuel pump keep on working?
As others have suggested elsewhere, if I suck and blow on the breather tube that leads to the carb from the crankcase, will that reliably confirm or deny that the breather valve is operational? Common sense leads me to believe that for the breather valve to be a cause for pressure to build up in the crankcase, it would have to be stuck in the closed position, but if it was stuck closed, wouldn't that mean I would NOT see oil coming out of the breather tube into the carb?
Thanks for your time and have a "Goo'day Mate" (hope that isn't offensive)
J R Clark