The two stroke KX 80 or KX 100 cylinder head is not boreable, like some other four stroke models, because of the type of metal used.  However, the cylinder can be re-sleeved.  Generally once the re-sleeve has taken place, then the cylinder becomes "boreable".  To date, we have overhauled our motor - replacing the crank in the bottom end, and using a standard size wiseco piston for the top end.  Information indicates the two stroke piston requires replacement (if under heavy use) about every 40 hours of operation.  The crank should remain OK, if the 32:1 mix is used.  Higher rations ( less oil in the gas mix ) of 38 or 40:1 will result in a siezed crank, which can be difficult to seperate ( but in most cases is replaceable ).