Super cheap super simple mechanical fuel pump.

This is absolutely brilliant. Turns out the rotary has a separate
compression chamber that pulses. Somewhat similar to a
2 cycle so it is REAL cheap to have a VERY VERY simple
and reliable mechanical fuel pump. This is not possible on
a four stroke  piston engine.

Another advantage of the Wankel rotary engine.

This is an AIXRO engine on an ultra light.