gotta add in my .02, i also have an o.s. .18 cv-rx(s) in my sportmaxx, first 2.5 was beatiful, second one was an absloute pain so i got this o.s. is has not stalled once (well during break in it did a couple times because it has to be so friggin rich). but other than that the thing will idle forever if you want it to. great power, havent changed either mixture screw in weeks, only thing is since i got it it leaks all over the crankcase with fuel, kinda lived with it but dirt got on the fuel and mudpies were all over my chassis near the engine. so ive cleaned it all up and spent 1/2 and hour examining everything throroughly and its gotta be the o-ring that goes under the carb, between it and the intake port on the crankcase, so i sent o.s. a LONG and DESCRIPTIVE email lol and they replied in less than a friggin day and asked for my address to send me a new gasket cuz they believed it was the gasket. so no biggie, i can understand if stuffs defective, its a very new engine, just came out, so my vote: kick-ass engine!