sadmar30 wrote:Considering if they use production blocks which have no provision for a balance shaft, they wont be able to run an odd fire inline four like yamaha.
sincere question here, are you saying the (cross-plane crank) Moto GP Yamaha of the last few years has a balance shaft ?
(IMO the Y wouldn't have more need for a balance shaft than a conventional 4 cyl has)
and another, surely a balance shaft is anyway more likely on a production (road) bike than on a racer ?
(especially in a fuel-limited race class)
large conventional (ie flat crank) 4 cyl road bike engines have balance shafts for vibration (rod angularity) at twice engine frequency
these IIRC cost eg 3 hp, and have been removed when racing where rules allow this
enlightenment, anyone ?