1955 thru 1957 Honda SA SB ME MF motors

[Boxler 65 Dream 305]

Does anyone have any knowledge of the differences in motors between the:
SA,ME 250
SB350
MF350
Ive read the 250SA and 250ME have about 11 horsepower and the SB350 has about 15 horsepower and the MF350 has about 20 horsepower. Besides the bore what differences are there between these motors? Do they all have the same stroke? Are the bottom ends all the same? If the SB350 and the MF350 are the same displacement where are they getting the extra 5 horse from on the MF 350? For example can a SA250 be modified with a SB350 or MF350 top end for more horsepower? I would guess that there may be carburetor,exhaust and camshaft changes also. If anyone has any knowledge on this topic I would really appreciate it!

[terecha]

hi!
Everything what you wrote is a true. Also valves are different.