1969 Ski-Doo Snowmobiles Service Manual, Page 7Get this manual
Figure "00" shows how this is possible through the use of three openings or ports; two ports open into the combustion chamber and the other one into the crankcase from the carburetorRotax use trans fer ports located on each side of the cylinderTherefore, ports at the time open into the combustion chamber (2 transfer and one (1) xhaust) Ignition
INTERNAL COMBUSTION ENGINES BASICS
Exhaust Compression