if the new sport is the same as my old one, then the barrel length don't come std bud, mines being top n tailed, hence why I have 2 x RB20 head gaskets to bring the squish up to a reasonable size, me thinks totalling 2.5mm

, (without looking back thru my notes)

as for the head, mines a porcupine 185 one opened up to 200cc.