Hi Mark..The valve seats were originally cut directly into the cylinder casting, so if you have valve seat inserts fitted they are a later addition.
If you don't have valve seat inserts fitted and the original seats have been recut to the extent that the valve/s are recessed into the cylinder face, the cylinder should be machined out and seat inserts fitted.
If you do have seat inserts fitted already but they are worn out the normal method of removal prior to fitting replacements is to machine them away.
If the original seats are pitted but not to the extent that the valves are recessed they can simply be recut and lapped in.
Finally, check the seat faces on the valves as well...particularly the exhaust valve to ensure there is no 'collapsing' of the valve seat face on the side nearest the cylinder, that they are not excessively pitted, that the 'land' above the seat face on the exhaust valve is adequate and the stems are not badly worn....Ian
email (option): ian@wright52.plus.com
Hi Mark...If you have an Automotoive Engineer in your area (that does rebores, crank grinds etc.) they can usually supply and fit a suitable hardened seat insert.
The very top edge of the valves seat face should be flush with the gasket face..with the land (or edge)of the valve above the seat protruding above the surface.
If you are unable to find somewhere to do the seat I can do it..the problem though is the cost of shipping the cylinder and the potential for damage during transit..they have to be very well packed..Ian