TPR Racing 84mm 305cc Big Bore Kit for Honda CBR 250
Ari Henning - Ride a CBR300R, CB300F, CB300R, Rebel 300, or a Grom, Monkey or CRF250L with a 300 engine swap? You can go from 286cc and a paltry 10.7:1 compression ratio
ASMIKE's CBR300R Build Thread | Honda CBR 300 Forum
TPR Racing 84mm 305cc Big Bore Kit for Honda CBR 250