RE: 25 Size Engine?
Unless you have offcial restrictions for the size, the .25 is not the best, I believe it is
better to get .35 where are the same weight you will get significant extra power,
in fact .35 is the same .25 where the displacement is made a big bigger and that
is just couple mm wide and tall.
Also, for those displacements Super tiger and especially MVVS are well known
to be very good ones at much lower cost than OS.