There's lots that can be done over factory 250s from '90s. Those 250 4-cylinders with 45bhp were actually restricted to comply with gentlemen's agreement between manufacturers. All had ways to remove this limit and get more power (Honda's smart-card may be most difficult to hack). Dave Moss's '93 CBR250RR gets 58bhp. Many, many people suspected he had 55-60bhp due to his laptimes before he posted his dyno-charts, which confirmed 58bhp. - With modern fuels, you can run 12.5-13.0:1 compression easily. Many factory bikes are running +13.0:1 with bigger bores than 250s - retard intake-cam timing to reduce factory high-RPM torque-drop with same redline. Use variable-cam timing to reduce low vs. high-end compromise. - 3D ignition-mapping. Don't have to compromise partial-throttle response. MC22s have retarded ignition-timing at HP-peak to reduce power. - yeah, EFI can get you +10% over carbs. Add that to Dave Moss's 58bhp and we're looking at 64bhp!