The original engines were 28 hp ( 21 kW ) Rotax 277s with 35 hp ( 26 kW ) Rotax 377 engines as optional .
Some aircraft have been modified with larger engines .
The original engines were 28 hp ( 21 kW ) Rotax 277s with 35 hp ( 26 kW ) Rotax 377 engines as optional , although some aircraft have been modified with larger engines .