Hello Barry, The one great advantage of alloy pistons is their weight. The other advantage is their modern make up in regards to heat expansion. Now my opinion is that when you give them to an engine reconditioner he will want to use modern bike tolerances. I still like to use the old rule .003 thou per inch of clearance. This will still give you rattle free performance and a little more insurance against seizure and maybe destruction of your crank. I am also a believer of giving a little more clearance to the rear pot particularly in regard to it running at much higher temperature. Somewhere in the handbook it says that the oil drip should be set in such a way as to to achieve a fine wisp of smoke from the exhaust when riding. This I dont think would happen if you use modern tolerances. Open to critism on my thoughts from other operators. regards Al
