I know that he did a 61cc twin based on the Echo CST-610 chainsaw. I have one converted and 4 more here waiting. I have been told that there was another size twin that was under 100cc that may have used the same crank but have not been able to figure out what it was or is. I would like to know what it was as I would like to make one of the ones I have into it. Problem would be the stroke of the original engine and finding cylinders with that stroke but a bigger bore. Then matching the cylinder alignment dowels. D&B makes the 61cc also.