Oversize Cam and Lifter Spindles
When you discover the holes in your crankcase for the cam and lifter spindles are oversize it is not a problem. Oversize spindles are available.
What you have to remember when offering the new oversize spindles, unless corrected, the holes will not be oversize for the full depth of the hole. It is at this point one must be aware that spindle lengths can vary. Without correcting the diameter of the hole you may find yourself trying to drive a spindle home where the end of the spindle is facing a .004" or more interference fit. The pressure this heavy interference causes is is enough to crack the crankcase especially on the rear cam spindle. To quote an English friend of mine, This is a confounded nuisance."
To avoid this the spindle can be shortened a bit, but I find it better to ream the hole to correct the problem. This way the hole is straight and true and you don't risk breaking the crankcase.
Fitting New Sleeves to your Muffs
With time and heat cycles Vincent muffs loose the .006" interference fit that holds the sleeve in place. This causes all sorts of problems. Select an oversize sleeve that will give you the required .006" interference fit. Bore and hone the aluminum muff so the new oversize sleeve has the required .006" interference. For good heat transfer get the surface finish on the muff as smooth as possible.
When heating the muff getting it to 250° F is about all that is required. At that temperature you will have at least .001" to .0015" clearance on the new sleeve. When the temperature is reached let the muff soak up the heat for 5 minutes or so to allow it to grow before you offer the sleeve.
To avoid having the sleeve squeeze up out of the muff as it cools hold the sleeve up from dropping fully home. I place a 1/4" piece of metal along side the sleeve as I drop it. A 1/4" or so is all you need. When the assembly is cool enough to handle go to the press and finish pressing the sleeve home. This way the sleeve's shoulder is pressed firmly against the head avoiding problems later when the sleeve settles in the muff and you loose the seal between the head and the top of the sleeve.
It makes for easier going if you do some planning and have the tools and accessories at hand before you start. You will need something to hold the muff up of the table to allow the sleeve to drop through the sleeve. You will need a 1/4" piece of steel to rest against the side of the sleeve, you will need to adjust your press so it is at the right height to do the job, you will need a stiff plate to hold the muff/sleeve assembly in the press and another to place on top of the sleeve to press on.