I recently got a 21cc? Echo,at least thats what I was told it was,does look like my blower,to try on gas/glow. Using the 10/10 1-3 gas ratio it turned 15-8 6700 rpm 16-8 5900 .I took muffler off and rpm would increase 500 rpm. It will idle at 1400 and has a good transition with glow power on.
I am using a zenoah 20 muffler and the prop stud [goes from 6mm at crank to 8mm at prop] works also.I did have to ream muffler holes slightly for easy fit but for $8 new what a deal. I tried the original muffler but 6000 was the best on any prop,
Are these figures about right for this engine? I am really surprised how docile this engine is, reminds me of my 135 Moki but without all the rpm.
It seems like the 15-8 or maybe a 16-6 might be best. Looking forward to getting it on something and flying.