I have a Reedy .21 motor and I did the break in process just buy the book...I have almost half a gallon thru it......When cranked it idles perfect and when you bump the throttle no problem...But when you give it alot of throttle and let off it just dies...I have played with the lean and rich..glow plugs and even the different carb. sleeves......I was wondering if maybe I should seal the engine...and if I should seal it what should I use to seal it....we maybe you can help...THANKS

If you are running it down the straight and then it dies it sounds like it is running out of fuel, a sign of being to lean.

Yes on above but you also might be too low of idle for it to bump back. Make sure when your tuning it you get it up to running temp first. Love my Reedy!!!