I just rcvd my rcv 91-cd, and have run a couple of tanks through it, all I have to say is what a great engine, started first spin, ran great, seemed like it had more than enough power, followed RCV's Running in instructions, Ran for 15 min, and 15min cool down time, fired it up, set the high end, then set idle, very quite compared to OS & Saito, very distinct sound(average joe may not be able to distinguish) but our flying club has many 4 strokes so I noticeed the minute differences. I will continue to post when engine has had more run time, first in the CG super chipmunk, and then moving it into the new great planes Super Skybolt ARF when it arrives.