Reply to thread

Message: [QUOTE="EricGorr, post: 158644, member: 19611"] Hi Bill, Measuring the piston and setting the clearance on 4-stroke thumper pistons can be a bit tricky, every company seems to have some idea on how to do it. J&E says to measure the edge of the slipper skirt and set the bore size to the same dimension, assuming that the skirt will collapse .002in. upon start-up. I set the bore size to 97.01mm to account for slight differences in pistons, the model you have should measure 96.950 out of the box. You're still safe with .0033in. clearance. Its amazing that you removed 40 grams from that piston, thats a ton when you spin it to 12 grand! Regarding the honing accuracy, US Chrome uses a CNC honing machine with all-abrasive anti-rollover mandrels. That set up is really beneficial for large 4-stroke cylinder bores. Most of the other plating vendors are using horizontal hand-feed single-row stone honing machines. I use that same set up for my 58mm and smaller 2-stroke cylinders too. Its very tooling and skill dependent to get any decent result, but its also easy to change surface finishes for various degrees of plateau finish. The modern lightweight slipper piston on the big thumpers require a very round bore to take advantage of the piston's unique shape. Keep us updated on how your YZF performs with your lightening mods on the piston. Thanks, Eric P.S. What do you think about counter-boring the top of the cylinder to fit a ring of copper-berylium as a heat sink and anti-detonation gaurd? Thats starting to become common on plated NASCAR blocks. [/QUOTE]

Verification: Which ocean is California closest to?