I'm willing to bet your low RPM is due to two factors: 1) New Engine and 2) You said it was way rich, which isn't bad. WE got mine adjusted but weren't able to put a tachometer on it. Two things to try are to properly adjust the carb and if you're still not getting good numbers after at least two gallons, cut off ends of the pipes on the muffler with a dremel. The holes look pretty big to me if we have the same muffler. About the same as the Slimline DA 50 muffler which is often modified for this engine and gets the same numbers as the set up on a can. I wish Slimline would make mufflers for this engine, but i'm not King yet. I know the engine likes to turn somewhere around upper 6700's to lower 6900's in the RPM range. It'll probably happen once you lean it out a little bit and get some time on it though. I wish the snow would melt so I could maiden my Edge and see what this engine can do.