Orma, I don't know about the R version, but the "regular" EFS series of carb requires more than gravity feed to run, so it won't just run out with no pump pressure behind it. My limited experience with my EFS-3A is that the engine needs to be sucking on it in order for it to flow anything more than idle amounts of fuel. In fact, the first time you run it, you have to suck on the port with a piece of plastic tubing to make it flow at all if you don't have a primer. First thing I'd do tomorrow is call Ben Ellison at 425-271-3220 and ask him what he thinks. You've probably seen it already, but there's some info on that carb on their website at http://www.ellison-fluid-systems.com/applications/rotax582.htm , and you'll find a lot more on these carbs and what makes them special in that general vicinity.
As far as Ellisons in general go, I'll quote Steve Makish, who's tried just about every carb on VWs, Subarus, and now the Corvair...."you can screw around with the rest all you want, but when you get tired of fooling around, get out your wallet and buy an Ellison, and you'll be done with it". I'm pretty happy with mine, that's for sure, but I haven't flown it either. Other comments by somebody who knows what they are talking about are certainly welcome. I'm just throwing this out there because I'm afraid it's all you're going to hear... Mark Langford, Huntsville, Alabama N56ML "at" hiwaay.net see KR2S project at http://home.hiwaay.net/~langford
