Quote Originally Posted by andreww5680 View Post
Strictly speaking to skim a head you should make up a jig that holds the head exactly parallel then put it on a surface grinder and grind off the minimum amount to take off all the high spots. The same should be done with the barell. Since i know a local engineering company they lent me some ground flat stock (flat steel plate approx 30mm thick with a surface ground face typically used for machine tooling etc) - as this is very flat i put some very light emery paper on the surface and put the head and barell face down then rotated them while holding the paper until you could see that the high spots had been removed.

This method has been used by a number of my associates on other motorbikes and could save a hefty machining bill !!

No there is no impact on engine timing - obviously you have to dismantle the engine and thus upon reassembly it needs to be re timed - this isnt really that much of a chore though. Obviously if you were to take a lot of material off the faces of the head and barell it would

a) increase the compression
b) if too much was taken off the vales and piston could collide

Right everyone enjoy your nap !!!!!
an old friend uses a pane of glass for cleaning up head and cylinder surfaces when using this method.goodluck with the rest of the build...tractor.