Ernie, BME started with their 5.8ci/100cc twin, and added a new crankshaft with a longer stroke bring up the size to 6.2ci/102ccs using spacer plates under each cylinder jug. Then came a new crankcase with no spacers and a bit longer nose, still a 102. The EVO had a further improved crankcase a bit lighter still, but whose main claim to fame was the larger and better breathing reed valve assembly.