Martin;  I don't remember ever taking the sleeves out of any of my engines,  As I understanding it, the last Drown that I sent you, popped and sounded like a AK47.  If it would run on the prime then I suspect that there is something wrong with the needle valve assembly, You state that when you choke it it draws fuel well so I'm not sure what the problem is.  You may remember the Yellow WWI biplane that I built but never flew was if I remember correctly, was susposed to use that last Drone.  That was the last engine, that I used in my Secret Weapon but after the R/C meet in Summit, NJ, where a competitor "accidently" stepped on the wing. I stopped flying after that. I repaired the plane but it was never the same.  This was about the time we discovered girls and cars  Chris