Boyesen ports as they're called, short circuit the crankcase and allow charge directly into the transfer port. They also give the charge somewhere to go when the piston covers the intake ports instead of the charge "backing up" towards the reeds.
Boyesen ports as they're called, short circuit the crankcase and allow charge directly into the transfer port. They also give the charge somewhere to go when the piston covers the intake ports instead of the charge "backing up" towards the reeds.