Been searching for the mini four strokes out there that might be good for converting for rc and picked up a Stihl catalog at my local dealer to see the info on their 4 mix four strokes the 31cc & 36cc trimmers & found a backpack blower with a 4 mix four stroke at 65 cc and 4 hp. model number br 550 here is a link I hope.
http://www.stihlusa.com/blowers/BR550.html

Thanks Hubert