Syncing has nothing to do with the foam at all. fire the bike up and let it get warmed up, and then sync. All a sync does is get each of the throttle plates providing equal valccum across the cylinders. Changing the foam size affects the jetting. also be aware that if the fuel levels are running high, and you have to set the float heights higher than 18mm to get the levels down to 1mm above the parting line, then you need new needles. trust me on that - Steve